Updated on 2024/05/26

写真a

 
SASAKI Tomohiro
 
Organization
Academic Assembly Institute of Science and Technology SEISAN DESIGN KOUGAKU KEIRETU Professor
Faculty of Engineering Department of Engineering Professor
Title
Professor
External link

Degree

  • Doctor (Engineering) ( 2006.3   Yokohama National University )

Research Interests

  • Optics Welding and Joining Ultrasonic

Research Areas

  • Manufacturing Technology (Mechanical Engineering, Electrical and Electronic Engineering, Chemical Engineering) / Measurement engineering  / Optical measurement techniques

  • Nanotechnology/Materials / Material processing and microstructure control

  • Manufacturing Technology (Mechanical Engineering, Electrical and Electronic Engineering, Chemical Engineering) / Mechanics of materials and materials  / 材料接合

Research History (researchmap)

  • Niigata University   Graduate School of Science and Technology   Professor

    2020.4

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    Country:Japan

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  • Niigata University   Graduate School of Science and Technology Advanced Materials Science and Technology Advanced Mechanical Science and Engineering   Associate Professor

    2012.10

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  • Niigata University   Graduate School of Science and Technology   Associate Professor

    2012.10 - 2020.3

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  • Niigata University   Faculty of Engineering Department of Mechanical and Production Engineering Creative Engineering   Assistant Professor

    2009.4 - 2012.9

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  • Southeastern Louisiana University   Research fellow

    2008.7 - 2009.3

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  • Yokohama National University   Research Associate

    2007.4 - 2009.3

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  • Yokohama National University   Assistant

    2006.4 - 2007.4

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Research History

  • Niigata University   Faculty of Engineering Department of Engineering   Professor

    2020.4

  • Niigata University   Graduate School of Science and Technology Advanced Materials Science and Technology Advanced Mechanical Science and Engineering   Associate Professor

    2012.10 - 2020.3

  • Niigata University   Faculty of Engineering Department of Mechanical and Production Engineering   Associate Professor

    2012.10 - 2020.3

  • Niigata University   Abolition organization Creative Engineering   Assistant Professor

    2009.4 - 2012.9

Education

  • 横浜国立大学大学院博士課程後期   工学府機能発現工学専攻

    2003.4 - 2006.3

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    Country: Japan

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  • Yokohama National University   Graduate School, Division of Engineering   機能発現工学

    - 2003.3

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    Country: Japan

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  • Yokohama National University   Faculty of Engineering   Department of Mechanical Engineering and Materials

    - 2001.3

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    Country: Japan

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Professional Memberships

Committee Memberships

  • 溶接学会   東部支部 代議員  

    2018.4   

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  • 日本鉄鋼協会北陸信越支部   幹事  

    2017.4   

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    Committee type:Academic society

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  • 溶接学会   界面接合研究委員会 幹事  

    2013.4   

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  • 日本金属学会 ヤングメタラジスト研究交流会   ヤングメタラジスト研究交流会 運営委員  

    2007.4 - 2009.3   

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    Committee type:Other

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Papers

  • Model development for numerical analysis of the bonding strength for friction welded lightweight structures

    Eric Heppner, Tomohiro Sasaki, Frank Trommer, Elmar Woschke

    Finite Elements in Analysis and Design   229   2024.2

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    The rotary friction welding (RFW) is a robust, precise, productive and economical joining process that is used in many areas of mechanical engineering to produce lightweight structures consisting of combinations of ferrous and non-ferrous materials, for instance aluminium alloy and steel. Crucial for the design of such lightweight structures is the knowledge about the bonding strength. The bonding strength is the result of the bond formation depending on the present transient kinematic, kinetic and thermal states during the welding process being directly determined by the welding process parameters. Despite several years of empirical research, no reliable numerical modelling approach exists for the RFW process to analyse the bonding strength based on these transient state variables. For this reason, an improvement of the bond formation and therefore an increase in the bonding strength can only be tested experimentally. The main motivation of this paper is to develop an appropriate modelling approach for the estimation of the bonding strength for friction welded lightweight structures manufactured of an aluminium alloy and a structural steel. Therefore, a couple of aluminium alloy and steel welding experiments with different process parameters were performed and subsequently analysed concerning to the resulting bonding strength. Moreover, all the welding experiments were simulated in regard to the corresponding welding process in order to determine the present kinematic, kinetic and thermal state variables, like the strain rate, the stress and the temperature. Thus, a model for the characterization of the bond formation can be developed, which allows a correlation between the bond formation and the resulting bond strength based on the chosen welding process parameters. Finally, the model will be examined and discussed in terms of its plausibility and applicability.

    DOI: 10.1016/j.finel.2023.104063

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  • In Situ Observation of Bubbles and the Effect of Ultrasonic Vibration on Bubble Behavior in EDM

    Chenxue Wang, Tomohiro Sasaki, Atsutoshi Hirao

    Materials   16 ( 20 )   2023.10

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    Accumulation and concentration of debris in deep hole electrical discharge machining (EDM) significantly hinder its machining efficiency and accuracy. It is believed that the movement of bubbles associated with the discharge gap flow field play a pivotal role in debris removal and influence the discharge conditions. Ultrasonic vibration (USV) of the electrode is thought to be an effective method for improving EDM-generated bubbles and debris exclusion. In this study, we first elucidated the behavior of bubbles during EDM of holes with varying aspect ratios. Subsequently, USV was introduced to EDM. The behavior of dielectric fluid flow under the influence of ultrasonic vibration was analyzed using computational fluid dynamics (CFD), which revealed time-varying changes in discharge gap flow pressure and velocity. The velocity of the dielectric flow field near the electrode’s side face was found to reach a maximum of approximately 15.2 m/s, greatly facilitating debris removal. High-speed camera observations revealed that bubbles were dispersed within the side gap, with most of them adhering to the electrode’s wall. Furthermore, the bubbles exhibited a tendency to continuously break up and coalesce near the hole’s outlet before escaping in the USV-assisted EDM. These observed characteristics of bubble behavior under the influence of USV are expected to significantly enhance debris removal and promote efficient dielectric exchange.

    DOI: 10.3390/ma16206676

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  • Stress Dependence on Relaxation of Deformation Induced by Laser Spot Heating. Reviewed International journal

    Yuma Murata, Tomohiro Sasaki, Sanichiro Yoshida

    Materials (Basel, Switzerland)   15 ( 18 )   2022.9

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    This paper deals with a non-destructive analysis of residual stress through the visualization of deformation behaviors induced by a local spot heating. Deformation was applied to the surface of an aluminum alloy with an infrared spot laser. The heating process is non-contact, and the applied strain is reversible in the range of room temperature to approximately +10 °C. The specimen was initially pulled up to elastic tensile stress using a tensile test machine under the assumption that the material was subject to the tensile residual stress. The relaxation behaviors of the applied strain under tensile stress conditions were evaluated using contact and non-contact methods, i.e., two strain gauges (the contact method) and a two-dimensional electronic speckle pattern interferometer (non-contact method). The results are discussed based on the stress dependencies of the thermal expansion coefficient and the elasticity of the materials.

    DOI: 10.3390/ma15186330

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  • Accuracy verification of cortical bone thickness in terms of anteroposterior knee X-ray image. Reviewed

    高根沢佑斗, 森清友亮, 坂上勇太, 森隆裕, 古賀良生, 望月友晴, 古賀寛, 坂本信, 小林公一, 田邊裕治, 佐々木朋裕

    臨床バイオメカニクス(Web)   43   2022

  • Heat deformation analysis using a finite element model on gas pressure welding for railway rail Reviewed

    ITOH Hajime, YAMAMOTO Ryu-ichi, SASAKI Tomohiro

    QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY   40 ( 1 )   44 - 55   2022

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    Language:Japanese   Publisher:JAPAN WELDING SOCIETY  

    We developed heat deformation analysis model based on that of steel bar using Gaussian distribution in order to quantitatively understand deformation behavior of gas pressure welding of rail. The validity of the developed analysis model was confirmed by the variation of temperature, transition of upset length and geometry of budge through gas pressure welding test of rail. Therefore, it was confirmed that this model could simulate that with high accuracy. We found that the deformation degree at the center of the rail base and the jaw part of the rail head are smaller than that of other parts from results of heat deformation analysis. It is estimated that the deformation degree depends on the shape of rail. This paper describes the developed heating deformation analysis model of gas pressure welding of rail, and its validation test results.

    DOI: 10.2207/qjjws.40.44

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  • Dynamic ESPI Evaluation of Deformation and Fracture Mechanism of 7075 Aluminum Alloy Reviewed International journal

    Shun Takahashi, Sanichiro Yoshida, Tomohiro Sasaki, Tyler Hughes

    Materials   14 ( 6 )   1530 - 1530   2021.3

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:MDPI AG  

    The deformation and fracture mechanism in 7075 aluminum alloy is discussed based on a field theoretical approach. A pair of peak-aged and overaged plate specimens are prepared under the respective precipitation conditions, and their plastic deformation behaviors are visualized with two-dimensional electronic speckle pattern interferometry (ESPI). The in-plane velocity field caused by monotonic tensile loading is monitored continuously via the contour analysis method of ESPI. In the plastic regime, the peak-aged specimen exhibits a macroscopically uniform deformation behavior, while the annealed specimen exhibits non-uniform deformation characterized by a localized shear band. The occurrence of the shear band is explained by the transition of the material’s elastic resistive mechanism from the longitudinal force dominant to shear force dominant mode. The shear force is interpreted as the frictional force that drives mobile dislocations along the shear band. The dynamic behavior of the shear band is explained as representing the motion of a solitary wave. The observed decrease in the solitary wave’s velocity is accounted for by the change in the acoustic impedance with the advancement of plastic deformation.

    DOI: 10.3390/ma14061530

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  • Nondestructive Evaluation of Solids Based on Deformation Wave Theory Reviewed

    Sanichiro Yoshida, Conor McGibboney, Tomohiro Sasaki

    APPLIED SCIENCES-BASEL   10 ( 16 )   2020.8

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    The application of a recent field theory of deformation and fracture to nondestructive testing (NDT) is discussed. Based on the principle known as the symmetry of physical laws, the present field theory formulates all stages of deformation including the fracturing stage on the same theoretical basis. The formalism derives wave equations that govern the spatiotemporal characteristics of the differential displacement field of solids under deformation. The evolution from the elastic to the plastic stage of deformation is characterized by a transition from longitudinal (compression) wave to decaying longitudinal/transverse wave characteristics. The evolution from the plastic to the fracturing stage is characterized by transition from continuous wave to solitary wave characteristics. Further, the evolution from the pre-fracturing to the final fracturing stage is characterized by transition from the traveling solitary wave to stationary solitary wave characteristics. In accordance with these transitions, the criterion for deformation stage is defined as specific spatiotemporal characteristics of the differential displacement field. The optical interferometric technique, known as Electronic Speckle-Pattern Interferometry (ESPI), is discussed as an experimental tool to visualize those wave characteristics and the associated deformation-stage criteria. The wave equations are numerically solved for the elastoplastic stages, and the resultant spatiotemporal behavior of the differential displacement field is compared with the experimental results obtained by ESPI. Agreement between the experimental and numerical results validates the present methodology at least for the elastoplastic stages. The solitary wave characteristics in the fracturing stages is discussed based on the experimental results and dislocation theory.

    DOI: 10.3390/app10165524

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  • Deformation Wave Theory and Application to Optical Interferometry Reviewed

    Sanichiro Yoshida, Tomohiro Sasaki

    MATERIALS   13 ( 6 )   2020.3

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    A method to diagnose the deformation status of solid objects under loading is discussed. The present method is based on a recent field theory of deformation and fracture and optical interferometry known as the Electronic Speckle-Pattern Interferometry (ESPI). Using one of the most fundamental principles of physics referred to as symmetry in physics, this field theory formulates all stages of deformation and fracture on the same theoretical basis. In accordance with the formalism, the theory has defined the criteria for different stages of deformation (linear elastic, plastic and fracturing stages) expressed by certain spatiotemporal features of the differential displacement (the displacement occurring during a small time interval). The ESPI is used to visualize the differential displacement field of a specimen as two-dimensional, full-field interferometric fringe patterns. This paper reports experimental evidence that demonstrates the usefulness of the present method. A tensile load is applied to an aluminum-alloy plate specimen at a constant pulling rate and the resultant in-plane displacement field is visualized with a two-dimensional ESPI setup. The differential displacement field is obtained at each time step and the interferometric fringe patterns are interpreted based on the criterion for each stage of deformation. It has been found that the criteria of linear elastic deformation, plastic deformation and fracturing stage are clearly observed in the corresponding fringe patterns and that the observations are consistent with the loading characteristics.

    DOI: 10.3390/ma13061363

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  • Heat deformation analysis using a finite element model on gas pressure welding for steel bar Reviewed

    ITOH Hajime, YAMAMOTO Ryu-ichi, SASAKI Tomohiro

    QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY   38 ( 4 )   418 - 428   2020

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    Language:Japanese   Publisher:JAPAN WELDING SOCIETY  

    Finite element model of gas pressure welding of steel bars is constructed in order to evaluate deformation behavior of the welded joint. The proposed model is based on a thermal-structural coupled analysis. Distribution of heat flux sourced from oxy-acetylene flame is assumed as a combination of two Gaussian functions, and heat losses due to convection and radiation are considered. Temperature dependences of thermal and mechanical properties of welding materials is modeled for the thermal-structural analysis. The analysis results show a good agreement with experimental results of variations of the temperature and the displacement on the weld center in the 20MPa to 40MPa range of the welding pressure. The proposed model revealed that tensile strain on the weld interface reaches larger value in the center than that in the outside of steel bar, depending on the temperature gradient. Additionally, the difference of the tensile strain between the center and the surface increases with increasing the upset force. It is considered that the temperature gradient on the weld interface is an important factor to control the deformation of gas pressure welded joint.

    DOI: 10.2207/qjjws.38.418

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  • Effect of Residual Stress on Thermal Deformation Behavior Reviewed

    Tomohiro Sasaki, Sanichiro Yoshida, Tadashi Ogawa, Jun Shitaka, Conor McGibboney

    MATERIALS   12 ( 24 )   2019.12

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:MDPI  

    This paper discusses a non-destructive measurement technique of residual stress through optical visualization. The least amount of deformation possible is applied to steel plates by heating the specimens +10 degrees C from room temperature for initial calibration, and the thermal expansion behavior is visualized with an electronic speckle pattern interferometer sensitive to two dimensional in-plane displacement. Displacement distribution with the thermal deformation and coefficient of thermal expansion are obtained through interferometric fringe analysis. The results suggest the change in the thermal deformation behavior is affected by the external stress initially applied to the steel specimen. Additionally, dissimilar joints of steel and cemented carbide plates are prepared by butt-brazing. The residual stress is estimated based on the stress dependence of thermal expansion coefficient.

    DOI: 10.3390/ma12244141

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  • Ultrasonic Bonding of Multi-Layered Foil Using a Cylindrical Surface Tool Reviewed

    Keisuke Arimoto, Tomohiro Sasaki, Yuhei Doi, Taewon Kim

    METALS   9 ( 5 )   2019.5

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    A cylindrical tool was applied for ultrasonic bonding of multi-layered copper foil and a copper sheet to prevent damage to the foil during bonding. The strength of the joints bonded with the cylindrical tool was comparable to that of the joints bonded with a conventional knurled tool. The effect of the cylindrical surface tool on bondability was investigated thorough relative motion behaviors between the tool surface and the bonding materials, as well as on bond microstructure evolution. The relative motion was visualized with in-situ observation using a high-speed camera and digital image correlation. At shorter bonding times, relative motions occurred at the bonding interfaces of the foil and the copper sheet. Thereafter, the relative motion between the tool and the bonding material became predominant owing to bond formation at the bonding interface, resulting in a macroscopic plastic flow in the bonded region. This relative motion damaged the foil in knurled tool bonding, and the cylindrical tool achieved bonding without any damage.

    DOI: 10.3390/met9050505

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  • Evaluation of Ultrasonic Bonding Strength with Optoacoustic Methods Reviewed

    Takumi Kamimura, Sanichiro Yoshida, Tomohiro Sasaki

    APPLIED SCIENCES-BASEL   8 ( 7 )   2018.7

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    This study reports the application of an optoacoustic method for evaluating the bonding strength of ultrasonically bonded joints in a non-destructive and non-contact fashion. It is proposed that the bonding strength is correlated with the resonant frequency of bonded joints. The bonding strength measured with a destructive tensile test roughly increased with the vibration time, however, it varied, causing the transitional and dispersed formation of micro-bonds at the bonding interface. Scanning Electron Microscopic observation of the fractured surface suggested that the bonding strength depends on the total bonded area of micro-bonds. Frequency response of the bonded joint was examined with a non-destructive method using a piezo-electric vibrator. The experiment revealed that the resonant frequency exponentially increased with the bonding strength. In addition, this vibration behavior was dynamically visualized with electronic speckle pattern interferometry (ESPI). The correlation between the bonded area and the resonant frequency is discussed based on finite element analysis. The results indicate the possibility for in-situ evaluation of the ultrasonic bonding strength.

    DOI: 10.3390/app8071026

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  • Analysis of ultrasonic welding process of mild steel and 5052 aluminium alloy Reviewed

    Tomohiro Sasaki, Tatsushi Nagai, Takehiko Watanabe

    Welding International   32 ( 2 )   95 - 102   2018.2

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    © 2017 Informa UK Limited, trading as Taylor & Francis Group. Ultrasonic welding of mild steel sheet (SPCC) and aluminium alloy sheet (A5052) was conducted using two different weld tips of a knurled tip (K-tip) and a curved shape tip without knurled edges (C-tip). Behaviours of the weld tip and the welded materials during the weld process were analysed using a high-speed camera observation and an image correlation. The C-tip welding shows a completely different displacement behaviour from the K-tip welding; a relative motion between the tool tip and A5052 in contact with the tip predominantly occurs in the C-tip in contrast to a relative motion between A5052 and SPCC observed in the K-tip. The joint strength using the C-tip was higher than that using the K-tip under the weld conditions in this study. It is demonstrated that the relative motion behaviour in the C-tip causes a macroscopic deformation of A5052 in the vibration direction. This phenomenon promotes growth of a bonded region, resulting in the increase of joint strength. It is surmised that Fe–Al intermetallic layer forms at the weld interface, and the joint strength consequently decreases for the longer weld time condition.

    DOI: 10.1080/09507116.2017.1346895

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  • Influence of tool edge angle on the bondability of aluminum in ultrasonic bonding Reviewed

    Tomohiro Sasaki, Kazuki Komiyama, Jonas A. Pramudita

    JOURNAL OF MATERIALS PROCESSING TECHNOLOGY   252   167 - 175   2018.2

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    A transitional stage in the relative motion was confirmed through in-situ observation using a high-speed camera and digital image correlation. In the earlier bonding time within the first 20 ms, relative motion predominantly occurred between the bonding materials, resulting in the formation of an initial bond at the bonding interface. The initial bond developed toward the vibration direction with increasing bonding time. The formation of a larger bonded region was observed at larger edge angles, resulting in greater joint strength. In the latter stage of bonding time beyond 50 ms, the relative motion between the tool edge and the bonding material became predominant because of bond formation at the bonding interface. The relative motion between the bonding tool and the bonding material caused macroscopic plastic flow in the bonding part when larger edge angles were used, leading to the observed increase in joint strength. The enhancement of bond creation at larger edge angles is discussed on the basis of finite element analysis focusing on the change in stress distribution at the bonding interface with the penetration of the tool edge.

    DOI: 10.1016/j.jmatprotec.2017.08.024

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  • Two-step diffusion treatment of aluminium-coated TiAl-based alloy Reviewed

    T. Sasaki, T. Yagi

    Surface Engineering   32 ( 11 )   809 - 815   2016.11

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    © 2016 Institute of Materials, Minerals and Mining. Aluminising of thermal sprayed TiAl-based alloys (49.1 at-% Al) was conducted by a two-step diffusion treatment at 700°C and 1100°C. The coating morphology is strongly dependent on the diffusion temperature; a poreless and thicker TiAl3 layer is obtained at a temperature of 700°C, while the intermediate layer predominantly grows at a temperature of 1100°C. In addition, the second diffusion treatment at 1100°C can also decrease the overall pore volume in the TiAl3 layer. In a cyclic oxidation test at 900°C in the air, TiO2 scale predominantly grows in pores and cracks that occur in the coating, and this promotes the oxidation. It is demonstrated that the two-step diffusion treatment improves the oxidation resistance of aluminide coating on TiAl-based alloys because of the formation of poreless TiAl3 and the crack suppression by the intermediate layer.

    DOI: 10.1179/1743294415Y.0000000032

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  • Opto-Acoustic Method for the Characterization of Thin-Film Adhesion Reviewed

    Sanichiro Yoshida, David R. Didie, Daniel Didie, Tomohiro Sasaki, Hae-Sung Park, Ik-Keun Park, David Gurney

    APPLIED SCIENCES-BASEL   6 ( 6 )   2016.6

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    The elastic property of the film-substrate interface of thin-film systems is characterized with an opto-acoustic method. The thin-film specimens are oscillated with an acoustic transducer at audible frequencies, and the resultant harmonic response of the film surface is analyzed with optical interferometry. Polystyrene, Ti, Ti-Au and Ti-Pt films coated on the same silicon substrate are tested. For each film material, a pair of specimens is prepared; one is coated on a silicon substrate after the surface is treated with plasma bombardment, and the other is coated on an identical silicon substrate without a treatment. Experiments indicate that both the surface-treated and untreated specimens of all film materials have resonance in the audible frequency range tested. The elastic constant of the interface corresponding to the observed resonance is found to be orders of magnitude lower than that of the film or substrate material. Observations of these resonance-like behaviors and the associated stiffness of the interface are discussed.

    DOI: 10.3390/app6060163

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  • Evaluation of near-surface stress distributions in dissimilar welded joint by scanning acoustic microscopy Reviewed

    Dong Ryul Kwak, Sanichiro Yoshida, Tomohiro Sasaki, Judith A. Todd, Ik Keun Park

    ULTRASONICS   67   9 - 17   2016.4

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    This paper presents the results from a set of experiments designed to ultrasonically measure the near surface stresses distributed within a dissimilar metal welded plate. A scanning acoustic microscope (SAM), with a tone-burst ultrasonic wave frequency of 200 MHz, was used for the measurement of near surface stresses in the dissimilar welded plate between 304 stainless steel and low carbon steel. For quantitative data acquisition such as leaky surface acoustic wave (leaky SAW) velocity measurement, a point focus acoustic lens of frequency 200 MHz was used and the leaky SAW velocities within the specimen were precisely measured. The distributions of the surface acoustic wave velocities change according to the near-surface stresses within the joint. A three dimensional (3D) finite element simulation was carried out to predict numerically the stress distributions and compare with the experimental results. The experiment and FE simulation results for the dissimilar welded plate showed good agreement. This research demonstrates that a combination of FE simulation and ultrasonic stress measurements using SAW velocity distributions appear promising for determining welding residual stresses in dissimilar material joints. (C) 2016 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.ultras.2015.12.006

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  • Effect of tool edge geometry in ultrasonic welding Reviewed

    Kazuki Komiyama, Tomohiro Sasaki, Yusuke Watanabe

    JOURNAL OF MATERIALS PROCESSING TECHNOLOGY   229   714 - 721   2016.3

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:ELSEVIER SCIENCE SA  

    Ultrasonic vibration was applied to a single AA1050 aluminum sheet, and relative motion between a weld tool and a specimen during ultrasonic welding was assessed. Weld tools with different knurled edges such as a trapezoidal pattern edge (trapezoidal edge) and a serrated pattern edge (serrated edge) were prepared in this study to investigate the effect of tool edge geometry on weld microstructure. Relative motion behaviors between weld tools and a specimen were analyzed with a high-speed camera and digital image correlation. A large difference was observed under the normal, force of 588 N. In this condition, relative amplitude of the serrated edge was larger than that of the trapezoidal edge, and the penetration of the serrated edge was lower than that of the trapezoidal edge. In the serrated edge, plastic flow in the microstructure occurred because of a greater temperature rise. The strength of the joints welded using the serrated edge was greater than that using the trapezoidal edges In addition, although smaller relative vibration was observed in both of the tool edges as the normal force increased, the serrated edge showed higher joint strength. These phenomena are discussed and related to the relative amplitude and penetration depth. It is suggested that the bonded area was enlarged by the plastic flow, thereby increasing joint strength. (C) 2015 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jmatprotec.2015.10.031

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  • Residual Stress Analysis Based on Acoustic and Optical Methods Reviewed

    Sanichiro Yoshida, Tomohiro Sasaki, Masaru Usui, Shuichi Sakamoto, David Gurney, Ik-Keun Park

    MATERIALS   9 ( 2 )   2016.2

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    Co-application of acoustoelasticity and optical interferometry to residual stress analysis is discussed. The underlying idea is to combine the advantages of both methods. Acoustoelasticity is capable of evaluating a residual stress absolutely but it is a single point measurement. Optical interferometry is able to measure deformation yielding two-dimensional, full-field data, but it is not suitable for absolute evaluation of residual stresses. By theoretically relating the deformation data to residual stresses, and calibrating it with absolute residual stress evaluated at a reference point, it is possible to measure residual stresses quantitatively, nondestructively and two-dimensionally. The feasibility of the idea has been tested with a butt-jointed dissimilar plate specimen. A steel plate 18.5 mm wide, 50 mm long and 3.37 mm thick is braze-jointed to a cemented carbide plate of the same dimension along the 18.5 mm-side. Acoustoelasticity evaluates the elastic modulus at reference points via acoustic velocity measurement. A tensile load is applied to the specimen at a constant pulling rate in a stress range substantially lower than the yield stress. Optical interferometry measures the resulting acceleration field. Based on the theory of harmonic oscillation, the acceleration field is correlated to compressive and tensile residual stresses qualitatively. The acoustic and optical results show reasonable agreement in the compressive and tensile residual stresses, indicating the feasibility of the idea.

    DOI: 10.3390/ma9020112

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  • Analysis of near weld stress field based on strain measurement and physical mesomechanics

    S. Yoshida, T. Sasaki, M. Usui, Ik K. Park

    Physical Mesomechanics   19 ( 1 )   41 - 54   2016.1

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    © 2016, Pleiades Publishing, Ltd. Stresses induced by welding are analyzed from the viewpoint of material deformation behavior. Strain gages are used to measure the residual stresses, and electronic speckle-pattern interferometry is used to analyze the response of the welded work to external force. A tensile load is applied to a butt-welded, thin-plate steel specimen, and the resultant strain field is analyzed with the electronic speckle-pattern interferometry. Comparison is made with the case of a nonwelded specimen of the same material and dimension. The analysis indicates that the residual stress due to welding makes the normal strain due to the external tensile load asymmetric. The asymmetry enhances shear and rotational modes of deformation, generating stress concentration at a point away from the weld where the residual stress is substantially negligible. The observed features are discussed based on physical mesomechanics. Analysis reveals plastic deformation like behavior in the response of the welded specimen to the external force.

    DOI: 10.1134/S1029959916010057

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  • Nondestructive Characterization of Thin Film System with Dual-Beam Interferometer Reviewed

    Hae-Sung Park, David Didie, Daniel Didie, Sanichiro Yoshida, Ik-Keun Park, Seung Bum Cho, Tomohiro Sasaki

    RESIDUAL STRESS, THERMOMECHANICS & INFRARED IMAGING, HYBRID TECHNIQUES AND INVERSE PROBLEMS, VOL 9   9   129 - 137   2016

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    A dual-beam Michelson interferometer has been built with two thin-film specimens configured as end mirrors. The two specimens have been prepared by coating a 10 nm thick titanium film on a silicon substrate and coating a 100 nm thick platinum over the titanium film. For one of the specimens, the silicon surface has been treated prior to the coating (the treated specimen). Each specimen is oscillated from the rear surface of the substrate with an acoustic transducer at a driving frequency ranging from 6 to 14 kHz, and the resultant film surface displacement is measured with the interferometer. The dual-beam configuration is important to compare the treated and untreated specimens under the same experimental conditions. The oscillation amplitude of the transducer's surface has been calibrated so that the specimens can be oscillated with the same acoustic amplitude for the entire frequency range. The study has confirmed our previous observation that the film-substrate interface of the treated specimen shows a resonance-like behavior near 8 kHz, exhibiting higher oscillatory displacement than the untreated specimen.

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  • Two-step diffusion treatment of aluminium-coated TiAl-based alloy Reviewed

    T. Sasaki, T. Yagi

    SURFACE ENGINEERING   32 ( 11 )   809 - 815   2016

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    Aluminising of thermal sprayed TiAl-based alloys (49.1 at-% Al) was conducted by a two-step diffusion treatment at 700 degrees C and 1100 degrees C. The coating morphology is strongly dependent on the diffusion temperature; a poreless and thicker TiAl3 layer is obtained at a temperature of 700 degrees C, while the intermediate layer predominantly grows at a temperature of 1100 degrees C. In addition, the second diffusion treatment at 1100 degrees C can also decrease the overall pore volume in the TiAl3 layer. In a cyclic oxidation test at 900 degrees C in the air, TiO2 scale predominantly grows in pores and cracks that occur in the coating, and this promotes the oxidation. It is demonstrated that the two-step diffusion treatment improves the oxidation resistance of aluminide coating on TiAl-based alloys because of the formation of poreless TiAl3 and the crack suppression by the intermediate layer.

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  • Analysis of ultrasonic welding process of mild steel and 5052 aluminum alloy Invited Reviewed

    Sasaki Tomohiro, Nagai Tatsushi, Takehiko Takehiko

    Journal of Light Metal Welding   53 ( 11 )   448 - 454   2015

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    Ultrasonic welding of mild steel sheet <tt>(</tt>SPCC<tt>) </tt>and aluminum alloy sheet <tt>(</tt>A5052<tt>) </tt>was conducted using two di−erent weld tips of a knurled tip <tt>(</tt>K-tip<tt>) </tt>and a curved shape tip without knurled edges <tt>(</tt>C-tip<tt>)</tt>. Behaviors of the weld tip and the welded materials during the weld process were analyzed using a high speed camera observation and an image correlation. The C-tip welding shows a completely di−erent displacement behavior from the K-tip welding; a relative motion between the tool tip and A5052 in contact with the tip predominantly occurs in the C-tip in contrast to a relative motion between A5052 and SPCC observed in the K-tip. The joint strength using the C-tip was higher than that using the K-tip under the weld conditions in this study. It is demonstrated that the relative motion behavior in the C-tip causes a macroscopic deformation of A5052 in the vibration direction. This phenomenon promotes growth of a bonded region, resulting in the increase of joint strength. It is surmised that Fe-Al intermetallic layer forms at the weld interface, and the joint strength consequently decreases for the longer weld time condition.

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  • Ultrasonic brazing of magnesium alloy

    Takehiko Watanabe, Hideki Saito, Atsushi Yanagisawa, Tomohiro Sasaki

    Welding International   28 ( 3 )   184 - 189   2014.3

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    Authors tried to braze magnesium alloy in air using no flux with the aid of ultrasonic vibration, and investigated the effect of brazing conditions on the joint properties. The main results obtained in this study are as follows. Applying ultrasonic vibration made it possible to braze the magnesium alloy in air without flux and the joint strength was so high that the joint fractured partially in the base metal. The brazing temperature at which solid and liquid phases coexisted in filler metal could provide the brazed joint with the maximum tensile strength. This seemed to be because the liquid phase in the filler metal infiltrated into the cracks occurring in the oxide film on the faying surface during heating and the solid phase would rub against the oxide film to detach, resulted in removing the oxide film from the faying surface. The optimal time for applying ultrasonic vibration could effectually detach and remove the oxide film from the faying surface. The excessive applying time of ultrasonic vibration caused defects such as cavity formation in the brazed layer and led to decrease the joint strength. © 2014 Taylor & Francis.

    DOI: 10.1080/09507116.2012.715888

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  • Effect of tool geometry on ultrasonic welding process Reviewed

    Tomohiro Sasaki, Yutaro Sakata, Takehiko Watanabe

    INTERNATIONAL SYMPOSIUM ON INTERFACIAL JOINING AND SURFACE TECHNOLOGY (IJST2013)   61   2014

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    Ultrasonic welding of pure aluminum sheets is performed using two weld tools, one with a knurled surface and one with a cylindrical surface. Relative motion behaviors of each weld tool, with respect to the working materials, during ultrasonic welding tests are analyzed using the digital correlation method. Weld microstructure development is investigated on the basis of transitional weld stages in the context of relative motion behaviors. The dominant relative motion is between the two work materials at the beginning of the weld but changes to be the motion between the weld tool and the work material it is in contact with as weld time increases. Thermo-mechanical effects of the relative motion of the weld tool and the work materials, on the development of weld microstructure, are discussed.

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  • Effects of Ni and Co additions to filler metals on Ag-brazed joints of cemented carbide and martensitic stainless steel

    Kengo Kaiwa, Shinji Yaoita, Tomohiro Sasaki, Takehiko Watanabe

    Advanced Materials Research   922   322 - 327   2014

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    This study focuses on understanding the effect of Ni and Co additions to filler metals on Ag-brazed joints of cemented carbide and martensitic stainless steel. Ni and Co added braze alloys were processed based on Ag-Cu-Zn ternary alloy, and joint strength and microstructure of the brazed layer has been investigated. The joint strength increased by the 2.0mass%Ni and 0.5mass%Co addition into braze alloy. This trend is remarkable in the Co added alloy, and the brazed joint increased by 141% compared to that in no-added alloy. The joint strength was closely related to the suppression effect of Co dissolution from cemented carbide into filler layer and Fe diffusion from the stainless steel to the brazed layer. In the brazed microstructure, Co-depleted zone caused by dissolution of Co in the cemented carbide was observed near the interface between the cemented carbide and the steel. Width of the Co-depleted zone significantly decreased in the Co added alloy. However, the joint strength decreased in the multiple addition compared to that in the single addition of Ni or Co. © (2014) Trans Tech Publications, Switzerland.

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  • Ultrasonic spot welding of galvanized steel sheet

    Naho Kaneko, Tomohiro Sasaki

    Advanced Materials Research   922   332 - 337   2014

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    Ultrasonic spot welding of galvanized steel sheets has been conducted to investigate formation process of the weld microstructure, and effect of zinc coat on joint property. The joint strength showed a rapidly increase at the weld time of 0.8s, and it has the maximum value over 1.0 s. In the weld time range from 0.1s to 0.8s, fracture occurred in zinc coat/ steel interface. In contrast, the fracture partially occurred in the base steel in the weld time over 1.0s, and concaves in which the steel substrate of one specimen partially remains on the other specimen were observed. The formation process of weld microstructure of ultrasonic welding was proposed to be a two-steps process. First, zinc coat in the interface was mechanically removed by the vibration and clamping force, and some zinc particles dispersed in the weld interface. Second, the zinc particles melted due to the friction, and partially bonded regions were simultaneously formed around the zinc particles. The partially bonded regions were stirred with the steel substrate as the weld time increased. The joint strength increased by development of the stirred zone. At the weld time over 1.2s, the joint strength decreased due to growth of crack around the stirred zone. © (2014) Trans Tech Publications, Switzerland.

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  • Effects of Ni and Co elements in filler metals in Ag brazing of cemented carbide Reviewed

    S. Yaoita, T. Watanabe, T. Sasaki

    Materials Research Innovations   17 ( SUPPL 2 )   S142 - S147   2013.12

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    This study focused on understanding the reason for improvements in wetting characteristics to cemented carbide due to the Ni element in filler metals, and the effects of Ni element on the strength of brazed joints. Furthermore, the effects of Co element in filler metals on the strength of brazed joints were investigated. The results obtained are as follows. By adding Ni element to the filler metal, α-Cu solid solution phases were formed along the interface; consequently, the distribution of Ag and Co elements across the interface continuously changed. It appeared that the continuous distribution of Ag and Co elements across the interface caused the wetting characteristics to improve. Addition of Ni element expanded the Co depleted zone in the cemented carbide around the interface and decreased the strength of brazed joints. The addition of the Co element narrowed the Co depleted zone, resulting in an increase of the strength of brazed joints. © W. S. Maney & Son Ltd. 2013.

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  • Revealing load hysteresis based on electronic speckle pattern interferometry and physical mesomechanics Reviewed

    T. Sasaki, S. Yoshida

    PHYSICAL MESOMECHANICS   15 ( 1-2 )   47 - 57   2012.1

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    A method to reveal load hysteresis of metal specimens is described. In this method, a low-level tensile- load is applied to a previously loaded specimen, and the resultant displacement field is visualized as a two-dimensional, whole-field image. An optical interferometric technique known as the Electronic Speckle Pattern Interferometry is used for the visualization. The interferometric fringe pattern of the visualized displacement field is analyzed for determination of the degree of deformation from the previous load. A series of experiments have been conducted with aluminum plate specimens for the demonstration of this method. The specimens are preloaded to three stress levels: (A) lower than the yield stress, (B) middle of the plastic regime, and (C) close to the maximum stress. After released from the preload, the specimens are reloaded for fringe pattern analysis. It has been found that the fringe patterns clearly differentiate the three preloading conditions, and that by varying the reload stress level it is possible to reveal the preload stress quantitatively. All experimental observations are explained by deformation dynamics based on physical mesomechanics.

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  • Effects of Ni and Co Elements in Filler Metals in Ag-brazing of Cemented Carbide Reviewed

    Yaoita Shinji, Watanabe Takehiko, Sasaki Tomohiro

    Yosetsu Gakkai Ronbunshu/Quarterly Journal of the Japan Welding Society   30 ( 4 )   298 - 305   2012

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    Ag-based filler metals containing Ni element have been recommended for brazing of cemented carbide because the Ni element is considered to improve the wetting characteristics to the cemented carbide. However, the reason for the improvement is still unknown. The present study was aimed at clarifying the reason why the Ni element in Ag-based filler metals makes the wetting characteristics improved and the effects of the Ni element on the bending strength of the brazed joints. Ag-Cu-Zn ternary alloys with and without Ni element were produced to investigate the effects of the Ni element. Furthermore, Co element was added into the filler metals to prevent the Co element in the cemented carbide from diffusing into the brazed layer, and the effects of the Co element on the bending strength of the brazed joints were investigated. The obtained results in this study are as follows. By the Ni element addition into the Ag-based filler metal, a-Cu solid solution phases were formed in the brazed layer along the interface
    consequently, the distribution of Ag and Co elements across the interface between the cemented carbide and the a-Cu solid solution phases continuously changed. It seemed that the continuous distribution of Ag and Co elements across the interface caused the wetting characteristics to improve. The Ni element addition expanded the Co-depleted zone of the cemented carbide around the interface and decreased the bending strength of the joint brazed at 750 °C. However, when the brazing temperature was set at 850 °C, much amounts of Ni element diffused into the Co-depleted zone. As a result, the deterioration of the bending strength of the brazed joint was small. The Co element addition made the Co-depleted zone narrow, resulting in the increase of the bending strength of the brazed joints. © 2012, JAPAN WELDING SOCIETY. All rights reserved.

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  • Analysis for ultrasonic welding process of aluminum sheets using digital image correlation method Reviewed

    SASAKI Tomohiro, WATANABE Takehiko, GOTO Takuto, HOSOKAWA Yusuke, YANAGISAWA Atsushi

    QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY   30 ( 2 )   125 - 132   2012

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    Ultrasonic welding phenomenon of pure aluminum sheets was observed using high speed video camera. The dynamic vibration behaviors of the edges of a welding tip, and a pair of aluminum sheets (upper specimen, lower specimen) were analyzed from the captured images using digital image correlation method. The following results were obtained. The welding process was comprised of following three stages. First, the upper specimen vibrated accompanying with small slipping between the edge and the upper specimen. The upper specimen thereby moved to one side along the vibration direction (Welding process I). In the second process, the vibration amplitude of the upper specimen decreased, while the friction between the edge and the upper specimen relatively increased (Welding process II). Then, the vibration amplitudes of the upper specimen and the lower specimen increased and the welding region plastically deformed (Welding process III). Joint strength increased with the welding time. In the fracture surface observation, partially welded regions were observed in the welding time corresponding to the welding process I, and growth of the welded regions was confirmed in the welding process II. The maximum strength was obtained in the welding process III, while adhesion to the welding tip and breakage of welded joints caused by compressive plastic deformation of welding region occurred in some specimens. The edges of a welding tip penetrated to the upper specimen with friction and plastic deformation of the upper specimen during the welding processes I and II. The penetrated depth saturated in the welding process II and the tip indentation forms on the surface of upper specimen.

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  • Effects of Ni and Co Elements in Filler Metals in Ag-brazing of Cemented Carbide Reviewed

    YAOITA Shinji, WATANABE Takehiko, SASAKI Tomohiro

    QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY   30 ( 4 )   298 - 305   2012

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    Ag-based filler metals containing Ni element have been recommended for brazing of cemented carbide because the Ni element is considered to improve the wetting characteristics to the cemented carbide. However, the reason for the improvement is still unknown.<br>The present study was aimed at clarifying the reason why the Ni element in Ag-based filler metals makes the wetting characteristics improved and the effects of the Ni element on the bending strength of the brazed joints. Ag-Cu-Zn ternary alloys with and without Ni element were produced to investigate the effects of the Ni element. Furthermore, Co element was added into the filler metals to prevent the Co element in the cemented carbide from diffusing into the brazed layer, and the effects of the Co element on the bending strength of the brazed joints were investigated. The obtained results in this study are as follows.<br>By the Ni element addition into the Ag-based filler metal, &alpha;-Cu solid solution phases were formed in the brazed layer along the interface; consequently, the distribution of Ag and Co elements across the interface between the cemented carbide and the &alpha;-Cu solid solution phases continuously changed. It seemed that the continuous distribution of Ag and Co elements across the interface caused the wetting characteristics to improve. The Ni element addition expanded the Co-depleted zone of the cemented carbide around the interface and decreased the bending strength of the joint brazed at 750&deg;C. However, when the brazing temperature was set at 850&deg;C, much amounts of Ni element diffused into the Co-depleted zone. As a result, the deterioration of the bending strength of the brazed joint was small. The Co element addition made the Co-depleted zone narrow, resulting in the increase of the bending strength of the brazed joints.

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  • Oxidation resistance of Al-rich aluminide coating on TiAl based alloy by thermal spray and diffusion treatment Reviewed

    Takahiro Yagi, Tomohiro Sasaki, Takehiko Watanabe, Atsushi Yanagisawa

    Advanced Materials Research   409   820 - 825   2012

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    Al-rich aluminide coating on Ti-49.1at%Al alloys has been performed by two-step process of thermal aluminum spray and diffusion treatment. Effect of the diffusion time on the oxidation resistance, and the change of microstructures in the coating during the oxidation test in air at 900°C for 100 h were investigated. In the aluminized coating before the oxidation tests, formations of TiAl 3 on the outer layer and an intermediate layer consisting of Ti 2Al 5, TiAl 2, and Al-rich TiAl were observed. The intermediate layer developed by the diffusion treatment for 3600s. In the oxidation test over 50 h, the specimen diffusion treated for 3600 s exhibited the lower oxidation rate than that diffusion treated for 900 s. Multi-oxide scales of TiO 2 and Al 2O 3 were observed on the both surfaces of aluminized specimens. Large TiO 2 particles were observed on the specimen of t D = 900 s. It was found that the TiAl 2 layer developed during the oxidized specimen, while the thicknesses of Al- rich TiAl and TiAl 3 layer decreased by the growth of TiAl 2. © (2012) Trans Tech Publications, Switzerland.

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  • Brazing of cemented carbides at lower temperatures

    Shinji Yaoita, Takehiko Watanabe, Tomohiro Sasaki

    Advanced Materials Research   409   865 - 870   2012

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    Cemented carbides have been widely used for cutting tools because of their high hardness and abrasion resistance. Since the cemented carbides are so expensive, it is desirable to reuse a tool shank made of cemented carbides. For the reason, so far, a new blade of a tool has been brazed to used shanks. However, when cemented carbides are heated for brazing, heating inevitably causes the deterioration in the mechanical properties. This study was carried out to braze the cemented carbides at lower temperatures for reducing the deterioration of the shank. First of all, authors developed a new Ag-based brazing filler metal with a low melting point of about 605°C, and investigated the effects of the new Ag filler metal on the properties of a brazed joint. Moreover, Co element or Ni element was added into the Ag filler metal to make the bending strength of a brazed joint improved. The addition of Co element increased the bending strength of a joint and the strength was equivalent to that of a joint brazed at 750°C using a conventional Ag filler metal, but the addition of Ni element decreased the bending strength of a brazed joint. © (2012) Trans Tech Publications, Switzerland.

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  • Analysis for relative motion in ultrasonic welding of aluminium sheet Reviewed

    T. Sasaki, T. Watanabe, Y. Hosokawa, A. Yanagisawa

    Science and Technology of Welding and Joining   18 ( 1 )   19 - 24   2012

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    Ultrasonic welding of pure aluminium sheets was observed with a high speed video camera. The dynamic vibration behaviours of a welding tip and aluminium sheets were analysed using the digital image correlation method. The welding process consisted of the following three stages. First, the upper specimen in contact with the weld tip vibrated. The formation of partially welded regions was confirmed at this stage. Second, the vibration amplitude of the upper specimen decreased, while friction between the weld tip and the upper specimen increased. Growth of the partially bonded region was confirmed in the second stage. Third, the welding part began to plastically deform owing to the clamping force. The joint strength reached its maximum value at the third stage. The analysis demonstrated that the relative motion between the weld tip and the upper specimen predominantly affected the increase in joint strength. © 2013 Institute of Materials, Minerals and Mining.

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  • Analysis for relative motion in ultrasonic welding of aluminium sheet Reviewed

    T. Sasaki, T. Watanabe, Y. Hosokawa, A. Yanagisawa

    Science and Technology of Welding and Joining   18 ( 1 )   19 - 24   2012

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    Ultrasonic welding of pure aluminium sheets was observed with a high speed video camera. The dynamic vibration behaviours of a welding tip and aluminium sheets were analysed using the digital image correlation method. The welding process consisted of the following three stages. First, the upper specimen in contact with the weld tip vibrated. The formation of partially welded regions was confirmed at this stage. Second, the vibration amplitude of the upper specimen decreased, while friction between the weld tip and the upper specimen increased. Growth of the partially bonded region was confirmed in the second stage. Third, the welding part began to plastically deform owing to the clamping force. The joint strength reached its maximum value at the third stage. The analysis demonstrated that the relative motion between the weld tip and the upper specimen predominantly affected the increase in joint strength. © 2013 Institute of Materials, Minerals and Mining.

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  • Brazing of Cemented Carbide Using Ag-based Filler Metals with a Low Melting Point Reviewed

    YAOITA Shinji, WATANABE Takehiko, SASAKI Tomohiro

    QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY   29 ( 3 )   204 - 209   2011.12

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    The present study was aimed at producing new Ag-based filler metals that have a melting point lower than that of a conventional Ag-based filler metal (BAg-24) for brazing cemented carbide and possess the ability to provide a high strength joint of cemented carbide. Using an Ag-based filler metal with a lower melting point (BAg0) that was a quaternary alloy of Ag-Cu-Zn-Sn system previously developed by authors, and Ag-based filler metals with Ni or Co element added into the BAg0, cemented carbide rods were brazed. Bending strength of the joint and the brazed layer microstructure were investigated. The following results were obtained in this study.<br>Bending strength of a joint brazed at 650&deg;C using the BAg0 was about 85% that of a joint brazed at 750&deg;C using the BAg-24. When Ni element was added into the BAg0, intermetallic compounds were formed in the brazed layer, and bending strength of a brazed joint was decreased. By adding a small amount of Co element into the BAg0, bending strength of a joint brazed at 650&deg;C was improved and was equivalent to that of a joint brazed at 750&deg;C using the BAg-24. However, excessive addition of the Co element made the bending strength of a joint decreased.

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  • Development of Ag based brazing filler metal with low melting point Reviewed

    T. Watanabe, A. Yanagisawa, T. Sasaki

    SCIENCE AND TECHNOLOGY OF WELDING AND JOINING   16 ( 6 )   502 - 508   2011.8

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    This study was carried out to develop cadmium free silver based brazing filler metals that meet the following requirements. First, they have to have a melting point lower than that of BAg-1 brazing filler metal. Second, they have to have not only good wetting characteristics and the ability to produce a sound joint with excellent mechanical properties but also plastic formability. Using the calculated phase diagrams on Ag-Cu-Zn-Sn quaternary system alloys, the authors selected several alloys with a possibility of meeting the above requirements. The melting point and other properties, such as hardness and brazeability of the selected alloys, were evaluated. As a result, the authors successfully developed silver based brazing filler metals that have a low melting point below similar to 600 degrees C and meet the above requirements by adding a small amount of indium as an alloying element into the Ag-Cu-Zn-Sn quaternary system alloy. The newly developed brazing filler metals are slightly inferior in wetting characteristics to BAg-1; however, the brazing filler metal containing similar to 3 mass-% indium element showed wetting characteristics comparable to those of BAg-1. Furthermore, the new brazing filler metals could produce joints with a high tensile strength equivalent to similar to 83% of that of a joint brazed using BAg-1.

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  • Aluminizing of TiAl-based alloy using thermal spray coating Reviewed

    Tomohiro Sasaki, Takahiro Yagi, Takehiko Watanabe, Atsushi Yanagisawa

    SURFACE & COATINGS TECHNOLOGY   205 ( 13-14 )   3900 - 3904   2011.3

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    Coating of aluminide on a TiAl-based alloy (49.1 at.% Al) was carried out by thermal spraying pure aluminum and subsequent diffusion treatment at 1100 degrees C. The growth of a Ti-Al intermetallic layer in the coating layers during diffusion treatment for 120-1800 s as well as the oxidation resistance of the aluminized TiAl-based alloy was investigated. The outermost surface layer was comprised of Al-rich intermetallic TiAl3 and contained pores. In contrast, an Al concentration gradient layer consisting of Ti2Al5, TiAl2, and Al-rich TiAl containing 55 at.% Al was formed between the outermost layer and the substrate. The thickness of the outermost layer decreased with increasing diffusion time, while the thickness of the intermediate layer grew to approximately 30 pm. In addition, the coating/substrate interface changed from a wavy to a linear form with the growth of the intermediate layer. The aluminized coating, at all diffusion times, showed good oxidation resistance in cyclic oxidation tests at 900 degrees C in air. (C) 2011 Elsevier B.V. All rights reserved.

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  • Development of a nickel-based filler metal containing a small amount of silicon

    WATANABE Takehiko, WAKATSUKI Ken, YANAGISAWA Atsusi, SASAKI Tomohiro

    QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY   29 ( 4 )   241 - 247   2011

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    Authors tried to develop a new nickel-based brazing filler metal containing no boron and phosphorous to suppress the formation of brittle phases in a brazed layer. The properties of a joint brazed using the new filler metal were investigated and compared with those of a brazed joint using a conventional nickel-based filler metal of BNi-5. The following results were obtained in this study.<br>A new nickel-based brazing filler metal was successfully developed, which contains a small amount of Si and Mn and shows the melting temperature lower than about 1090&deg;C. The hardness of the new filler metal was about 40% that of BNi-5 filler metal containing about 10% Si.<br>In brazing of SUS304 stainless steel, using BNi-5 filler metal, a hard and brittle finally-solidified region appeared in the brazed layers with joint clearance over 100&mu;m. However, using the new filler metal, the finally-solidified region appeared in the brazed layers with joint clearance over 200&mu;m. The hardness of the finally-solidified region in the brazed layer using the new filler metal was about 54% that using BNi-5 filler metal.<br>The tensile strength of a SUS304 joint brazed using BNi-5 filler metal extremely decreased at joint clearance over 100&mu;m. On the other hand, the tensile strength of a joint brazed using the new filler metal decreased at joint clearance over 200&mu;m. It seems that the brittle finally-solidified region formed in a brazed layer causes the joint to decrease the tensile strength.<br>It was shown that the newly developed filler metal is superior to the conventional BNi-5 filler metal in hardness and in tensile strength of joints with wider joint clearance.

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  • Solid State Welding of CPTi and Aluminum Alloy Using a Rotating Probe Reviewed

    WATANABE Takehiko, YOSHIDA Ryou, YANAGISAWA Atsushi, SASAKI Tomohiro

    QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY   28 ( 2 )   255 - 260   2010.12

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    Authors tried to butt-joint weld commercially pure titanium plate to aluminum alloy plate by solid state welding using a rotating probe, and investigated the effects of welding conditions and intermetallic compound formed at the weld interface on the properties of the joint. The following results were obtained.<br>The titanium plate and the aluminum alloy plate were successfully butt-joint welded using a rotating probe. The tensile strength of the joint made under the optimum conditions was so high that the joint efficiency was about 97%.<br>The joint strength varied with the probe rotation speed and the offset. Fracture of the joint made under the optimum conditions occurred at the position in aluminum alloy, where the hardness was lower, 5&ndash;7mm away from the weld interface as well as at the interface between aluminum matrix and titanium fragments which were scattered around the weld interface.<br>By heating at 550&deg;C for 2h, intermetallic compound obviously appeared at the weld interface of the joint made under the optimum conditions. Fracture of the heated joint occurred at the weld interface, and the tensile strength and the elongation extremely decreased.

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  • Ultrasonic Brazing of Magnesium Alloy Reviewed

    WATANABE Takehiko, SAITO Hideki, YANAGISAWA Atsushi, SASAKI Tomohiro

    QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY   28 ( 1 )   80 - 85   2010.12

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    Authors tried to braze magnesium alloy in air using no flux with the aid of ultrasonic vibration, and investigated the effect of brazing conditions on the joint properties. The main results obtained in this study are as follows.<br>Applying ultrasonic vibration made it possible to braze the magnesium alloy in air without flux and the joint strength was so high that the joint fractured partially in the base metal. The brazing temperature at which solid and liquid phases coexisted in filler metal could provide the brazed joint with the maximum tensile strength. This seemed to be because the liquid phase in the filler metal infiltrated into the cracks occurred in the oxide film on the faying surface during heating and the solid phase would rub against the oxide film to detach, resulted in removing the oxide film from the faying surface. The optimal time for applying ultrasonic vibration could effectually detach and remove the oxide film from the faying surface. The excessive applying time of ultrasonic vibration caused defects such as cavity in the brazed layer and led to decrease the joint strength.

    DOI: 10.2207/qjjws.28.80

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  • Improvement of mechanical properties of ferritic stainless steel weld metal by ultrasonic vibration Reviewed

    Takehiko Watanabe, Masataka Shiroki, Atsushi Yanagisawa, Tomohiro Sasaki

    JOURNAL OF MATERIALS PROCESSING TECHNOLOGY   210 ( 12 )   1646 - 1651   2010.9

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    Authors investigated the effect of ultrasonic vibration on the solidification microstructure and mechanical properties of the weld metal of ferritic stainless steel by introducing directly ultrasonic vibration into the weld molten pool using ultrasonically vibrating filler metal. The main results obtained in this study are as follow.The ultrasonically vibrating filler metal could successfully transmit ultrasonic vibration to the weld molten pool. Ultrasonic vibration encouraged equiaxed grains to form in the central region of the weld metal. The more equiaxed grains formed due to ultrasonic vibration, the higher the welding speed was. The tensile strength of the weld with ultrasonic vibration was larger than that without vibration. The tensile fracture elongation of the weld with ultrasonic vibration remarkably increased compared to that without vibration. When the distance between an electrode tip and the filler metal was too short, the weld bead was less stably formed. (C) 2010 Elsevier B.V. All rights reserved.

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  • Development of Ag-based brazing filler metal with low melting point Reviewed

    WATANABE Takehiko, HWANG Inhye, YANAGISAWA Atsushi, SASAKI Tomohiro

    QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY   28 ( 4 )   402 - 407   2010

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    This study was carried out to develop cadmium-free silver brazing alloys that meet the following requirements. First, these alloys have the melting point lower than that of the BAg-1 brazing alloy, of which the melting point is the lowest in the conventional brazing alloys. Second, they have not only good wetting characteristics and the ability to produce a sound joint with excellent mechanical properties but also the plastic formability.<br>Using the calculated phase diagrams on Ag-Cu-Zn-Sn quaternary alloys, the authors selected several alloys with the possibility for meeting the above requirements. The melting point and other properties such as hardness and brazeability of the selected alloys were evaluated. As a result, the authors successfully developed the silver-based brazing alloys that had the low melting point below about 600&deg;C and met the above requirements by adding a small amount of indium as an alloying element into the Ag-Cu-Zn-Sn quaternary alloys. The newly developed brazing alloys were slightly inferior in wetting characteristics to BAg-1; however, the brazing alloy that contained about 3mass% indium showed the wetting characteristics comparable to BAg-1. Furthermore, the new brazing alloys could produce the joints with high tensile strength equivalent to about 83% of that of the joint brazed using BAg-1.

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  • Alloy Layer Structure Formed by High-temperature Aluminizing in Metal Mold Steel SKD61 Reviewed

    Odo Taisuke, Sasaki Tomohiro, Yakou Takao, Umeda Akihiro, Tomaru Masahide

    Tetsu-to-Hagane   95 ( 6 )   483 - 488   2009

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    The alloy layer formed by high-temperature diffusion treatments in the air after adhering of aluminum foil thickness from 5 to 50 &mu;m on metal mold steel SKD61 are examined. As a result, structural defect was not observed between FeAl and &alpha;Fe in the alloy of high temperature aluminizing, and the most stable alloying layer was formed at the case of the initial aluminum thickness was 15 &mu;m. The case of initial aluminum was thinner than 5 &mu;m at the long time diffusion and that was thicker, and than 5 &mu;m at the short time diffusion, structural defects were observed in the alloy layer. The former structural defect contained Cr oxide and aluminum oxide outside, and the latter structural defect contained void and high concentration of Cr. The stable alloy layer of high-temperature aluminized metal mold steel will be consist by Cr saluted FeAl and &alpha;Fe which has toughness without structural defects.

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  • Resistance spot welding of mild steel to magnesium alloy Reviewed

    WATANABE Takehiko, SUZUKI Yushi, YANAGISAWA Atsushi, SASAKI Tomohiro

    QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY   27 ( 3 )   202 - 207   2009

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    Authors tried to weld a steel plate to Mg alloy plate using a resistance spot welding method. In welding of the dissimilar materials, the authors employed SUS304 insert metal and investigated the effect of the insert metal and the electrode tip geometry on the strength of the welds. The following results were obtained.<br>When the steel plate was directly welded to Mg alloy plate without the insert metal, the temperature around the welded area and the strength of the weld increased with increasing welding current. The reason seems to be that the bonded area increases due to the increase in nugget diameter of Mg alloy and that the oxide film on the faying surface of the steel is easily reduced by the molten magnesium.<br>The insert metal of SUS304 with optimal thickness significantly improved the strength of the weld, however, the excessively thick insert metal increased the amount of magnesium expulsion and resulted in decreasing the weld strength.<br>The electrode tip with flat geometry attached a steel washer improved the strength of welds because the plunging depth of the electrode tip into the Mg alloy plate was decreased, resulting in the decrease of the molten magnesium expulsion.

    DOI: 10.2207/qjjws.27.202

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  • Formation of FeAl Layer on Carbon-Nitrogen Free Fe-12Ni-9Co-10W Austenitic Alloy by Aluminizing Treatment and Its Effect on Oxidation Behavior in Steam Reviewed

    Arikawa Shuichi, Muneki Seiichi, Okubo Hiroshi, Abe Fujio, Sasaki Tomohiro, Yakou Takao

    Journal of the Japan Institute of Metals and Materials   73 ( 4 )   255 - 261   2009

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    &nbsp;&nbsp;The effect of an aluminizing treatment on the oxidation behavior of carbon-nitrogen free Fe-12Ni-9Co-10W alloy has been investigated in steam at 973 K for 28 Ms. An FeAl layer with a thickness of 70 &mu;m was observed to form on the alloy surface during aluminizing treatment, which consisted of hot pressing of pure Al foil of 50 &mu;m thickness on to the sheet specimens at 523 K, and subsequent diffusion annealing at 1373 K for 3.6 ks in vacuum of 10<sup>-4</sup> Pa. The sheet specimens subjected to the aluminizing treatment exhibit excellent oxidation resistance in steam at 973 K, resulting from the formation of very thin Al<sub>2</sub>O<sub>3</sub> scale. Oxidation tests were carried out using specimens with a thin layer of FeAl, and specimens with no FeAl layer but different Al concentrations at the alloy surface. Excellent oxidation resistance was observed due to Al<sub>2</sub>O<sub>3</sub> scale formation when the FeAl layer was present or the Al concentration at the alloy surface with no FeAl layer was higher than 11%. When the Al concentration at the alloy surface with no FeAl layer decreased below 11%, thick scale of Fe<sub>3</sub>O<sub>4</sub> and Fe<sub>2</sub>O<sub>3</sub> formed during oxidation.<br>

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  • Effect of Si content on turning machinability of Al-Si binary alloy castings Reviewed

    Masatsugu Kamiya, Takao Yakou, Tomohiro Sasaki, Yoshiki Nagatsuma

    MATERIALS TRANSACTIONS   49 ( 3 )   587 - 592   2008.3

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    The effect of eutectic Si or primary Si on the machinability of Al-Si alloy castings, where eutectic Si or primary Si was served to improve the chip breakability were investigated. To enhance chip breakability, eutectic Si made the chips thin, and cracks that formed in primary Si during machining acted as nuclei for chip breaking. Eutectic Si had a stronger effect on surface roughness than primary Si, and eutectic Si reduced the adhesion on the cutting edge. The decrease in adhesion on the cutting edge led to a corresponding decrease in surface roughness. The cracking of primary Si was responsible for the increase in surface roughness in hypereutectic alloys. Tool wear increased with increasing amount of eutectic Si. In hypereutectic alloys, tool wear was accelerated by the contact between the tool and cracked primary Si.

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  • Tool wear and surface roughness during machining of high-temperature aluminized steel Reviewed

    Tomohiro Sasaki, Takao Yakou

    JOURNAL OF MATERIALS PROCESSING TECHNOLOGY   197 ( 1-3 )   89 - 95   2008.2

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    The machinability of high-temperature aluminized steel, wherein hot-dip aluminum-coated steel is heated to 1000 degrees C, was investigated by machining the material using a cemented carbide tool. It was confirmed that the alloy layer formed by the high-temperature aluminizing consisted of an Fe2Al5 layer, an FeAl layer and an aluminum solid solution (alpha Fe(Al)). With increasing diffusion time, the thickness of the FeAl layer and the aFe(AI) layer increased while the thickness of the Fe2Al5 layer decreased. During the machining of the aluminized steel at a cutting speed of 1.5 m/s, the tool temperature rose rapidly, in particular during cutting of the FeAl layer. Flank wear during cutting of the Fe2Al5 layer was not greatly affected by changing the cutting speed. In contrast, flank wear during cutting of FeAl was smaller at a lower cutting speed. The machined surface roughness was larger for cutting of the Fe2Al5 layer and the FeAl layer region because of brittle fracture on the machined surface, whereas it decreased with increasing distance from the surface to a minimum at the alpha Fe(Al) layer region. (C) 2007 Elsevier B.V. All rights reserved.

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  • Effects of heat treatment conditions on formation of Fe-Al alloy layer during high temperature aluminizing Reviewed

    Tomohiro Sasaki, Takao Yakou

    ISIJ INTERNATIONAL   47 ( 7 )   1016 - 1022   2007

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    Diffusion couples of Fe2Al5 and various substrates with different carbon content, pure iron, 0.27 mass% C steel and 0.45 mass% C steel were processed, and the formation of an Fe-Al alloy layer in the temperature range from 750 to 1000 degrees C was investigated. FeAl2, FeAl, and aluminum solid solution (alpha Fe(Al)) were confirmed in the alloy layer formed by heating the diffusion couples. Voids were generated inside the Fe2Al5 layer and near the interface between the FeAl layer and alpha Fe(Al) layer. The layer growth of FeAl and alpha Fe(Al) obeyed the parabolic law of the diffusion time, t(1/2). However, the thickness of FeAl saturated over a diffusion time longer than 3.6 ks at 950 degrees C because of the concentration of voids at the FeAl layer/alpha Fe(Al) layer interface and the disappearance of the Fe2Al5 layer. The activation energy for the formation of the FeAl layer in all kinds of the substrates was approximately 200 kJ/mol in the whole temperature range and the substrate. On the other hand, the activation energies for the alpha Fe(Al) layer in the 0.27 mass% C steel and the 0.45(1)mass% C steel were larger than that in pure iron at 750-800 degrees C.

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  • Effect of Si content on turning machinability of Al-Si binary alloy castings Reviewed

    KAMIYA Masatsugu, YAKOU Takao, SASAKI Tomohiro, NAGATSUMA Yoshiki

    Journal of Japan Institute of Light Metals   57 ( 5 )   191 - 196   2007

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    In this study, Al&ndash;Si alloy was employed as a specimen which added Si to improve the chip breakability, and the effect of eutectic Si and primary Si on the machinability of the Al&ndash;Si alloy was investigated. For chip breakability, eutectic Si made chip thin, and primary Si was cracked during machining and acted as a nucleus of chip breaking. For surface roughness, the effect of eutectic Si was higher than that of primary Si, and eutectic Si reduced the adhesion on cutting edge. The decrease of surface roughness resulted in a corresponding decrease in adhesion on cutting edge. Additionally, the cracking of primary Si was responsible for the increase of surface roughness in hypereutectic alloys. Tool wear was increased with an increase of the number of eutectic Si. In hypereutectic alloys, tool wear was accelerated by the contact between tool and crashed primary Si.

    DOI: 10.2464/jilm.57.191

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  • Machinability of intermetallic compound Fe3Al from the viewpoint of tool wear Reviewed

    Tomohiro Sasaki, Takao Yakou

    JSME International Journal, Series C: Mechanical Systems, Machine Elements and Manufacturing   49 ( 2 )   334 - 339   2006.12

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    The intermetallic compound Fe3Al was processed by a reactive sintering process, and its machinability from the viewpoint of tool wear was investigated using dry turning. In cutting Fe3Al with a cemented carbide tool, the tool life was approximately one tenth that of cutting carbon tool steel SK3 because of intense flank wear. The tool life for cutting Fe3Al using the cemented carbide P20 (WC-TiC-TaC-Co) tool was longer than for cemented carbide K10 (WC-Co). In addition, a cermet tool reached its tool life limit by chipping for the whole cutting speed range measured. The roughness of the machined surface of Fe3Al cut using a cemented carbide tool was much smaller than for SK3. However, for cutting using the cermet tool, the roughness showed a sharp rise due to chipping. It was found that the wear rate of the WC particles in the tool material is larger than TiC particles. The results of the study suggest that the cemented carbide P20 is suitable for cutting Fe3Al. Copyright © 2006 by The Japan Society of Mechanical Engineers.

    DOI: 10.1299/jsmec.49.334

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  • Features of intermetallic compounds in aluminized steels formed using aluminum foil Reviewed

    Tomohiro Sasaki, Takao Yakou

    SURFACE & COATINGS TECHNOLOGY   201 ( 6 )   2131 - 2139   2006.12

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    Foil aluminizing of steel, wherein Al diffuses to the base steel material by diffusion treatment after hot pressing of the aluminum foil at a lower temperature than the melting point, was performed in this study. Alloy layers formed by diffusion at temperatures ranging from 700 to 1000 degrees C were investigated, and their features were compared with those of hot-dip aluminized steel. In hot-dip aluminizing, an intermediate Fe2Al5 layer was formed between the aluminum layer and the base steel during aluminum coating before the diffusion treatment. In contrast, the coating layer of the foil-aluminized steel specimen after diffusion bonding of the aluminum foil consisted only of the Al layer. An Fe2Al5 layer, an FeAl layer and an Al diffused layer were formed in both the aluminized specimens subsequent to the diffusion treatment. The numbers of voids formed in the Fe2Al5 layer and at the FeAl/Al diffused layer interface of the foil-aluminized specimens are smaller than those for hot-dip aluminizing. Moreover, the FeAl and Al diffused layers are formed with a greater thickness in the foil-aluminized steel under identical diffusion conditions. The Al concentration in hot-dip aluminized steel decreased in stages from the surface to the base steel, whereas, in the foil-aluminized steel, it decreased gradually. The Fe(2)Al5/base steel interface in the foil-aluminized steel was thus indistinct, and cross-sectional hardness also decreased gradually. (c) 2006 Elsevier B.V. All rights reserved.

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  • Two-body abrasive wear property of cementite Reviewed

    T Sasaki, T Yakou, M Umemoto, Y Todaka

    WEAR   260 ( 9-10 )   1090 - 1095   2006.5

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    The abrasive wear property of single-phase cementite and cementite-iron composite, processed by mechanical alloying and spark plasma sintering, were investigated using a pin-abrasion test on fixed alumina abrasive grains. Single-phase cementite and cementite-iron composite had good wear resistances at applied pressures lower than 0.15 MPa. However, at applied pressures higher than 0.31 MPa, steels having a cementite volume fraction higher than 75% were intensely worn. In the former case, the wear mode of bulk cementite was ductile, and flow-type chips were observed on the worn surface. In the latter case, the wear mode was brittle, and brittle fracture chips were observed on the worn surface. (c) 2005 Elsevier B.V. All rights reserved.

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  • Effects of carbon contents in steels on alloy layer growth during hot-dip aluminum coating Reviewed

    T Sasaki, T Yakou, K Mochiduki, K Ichinose

    ISIJ INTERNATIONAL   45 ( 12 )   1887 - 1892   2005

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    Hot-dip aluminum coating of hypo-eutectoid steels containing 0.05-0.88 mass% carbon were performed, and the alloy layers formed in the coating were investigated. In the hot-dip aluminum coating at immersion temperatures ranging from 700 to 850 C, the alloy layers on the steels consisted of a single phase of the intermetallic compound Fe2Al5. The thickness of the alloy layer increased in proportion to the increasing square root of the immersion time (t(1/2)) for immersion temperatures lower than 800 C for the whole base steel. On the other hand, for immersion temperatures higher than 800 C, the thickness of the alloy layer on the 0.05 mass% C steel and 0.45 mass% C steels exhibited a negative deviation from the linear relationship. The growth rate constant k decreased as the carbon concentration of the base steel increased up to 0.8 %, above which k had a constant value. The reaction activation energies for the base steel in this study were approximately 70-80 kJ/mol. The alloy layer/base steel interfaces were serrated, and the serration width decreased with increasing carbon concentration of the base steel. In addition, the serration width had a larger value in the immersion temperature range wherein the pro-eutectoid ferrite content in the base steel was larger.

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  • Aluminizing Treatment of Mild Steel Using Aluminum Foil Reviewed

    SASAKI Tomohiro, YAKOU Takao

    Tetsu-to-Hagane   89 ( 12 )   1227 - 1232   2003.12

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    To obtain the ductile and corrosive coating treatment for steel, the aluminizing treatments using aluminum foil on mild steel surface were performed at diffusion temperature from 700 to 1000&deg;C. The foil aluminized steels had less voids in diffusion layers, than the hot-dip aluminized steels. The foil aluminized steels at diffusion temperature not higher than 800&deg;C had a thinner brittle layer of aluminum rich intermetallic Fe<SUB>2</SUB>Al<SUB>5</SUB>, and that at diffusion temperature not lower than 900&deg;C had thicker layers of iron rich intermetallics such as FeAl and Fe<SUB>3</SUB>Al. It was found that the three body abrasive wear rates of aluminized steels with FeAl and Fe<SUB>2</SUB>Al that diffused at not lower than 900&deg;C against free SiC grains were smaller wear rate than those of the steels diffused at higher than 800&deg;C.

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  • Two Body Abrasive Wear of Fe-Al Intermetallic Compounds Reviewed

    YAKOU Takao, SASAKI Tomohiro, KOBAYASHI Shigeaki

    Tetsu-to-Hagane   89 ( 11 )   1178 - 1182   2003.11

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    The abrasive wear behavior of specimens of Fe-Al intermetallic compounds (Fe<SUB>3</SUB>Al, FeAl, FeAl<SUB>2</SUB>, Fe<SUB>2</SUB>Al<SUB>5</SUB> and FeAl<SUB>3</SUB>) on SiC abrasive papers having an abrasive grain diameter ranging from 10 to 48 &mu;m were investigated. The relationship between the wear rate and the material hardness is classified into two cases. In the first case, the wear rate increases with decreasing specimen hardness when the specimen is worn using an applied force of less than 0.31 MPa and an abrasive grain diameter finer than 30 &mu;m. In this case, ductile wear is observed in all specimens. In the second case, the wear rate increases with increasing specimen hardness when the specimens are worn using an abrasive grain diameter coarser than 30 &mu;m. In this case, brittle wear is observed in the FeAl<SUB>2</SUB>, Fe<SUB>2</SUB>Al<SUB>5</SUB> and FeAl<SUB>3</SUB> specimens.

    DOI: 10.2355/tetsutohagane1955.89.11_1178

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  • 溶接・接合不完全部シリーズ 超音波接合における欠陥の原因と対策—Causes and remedies for weld defects in ultrasonic bonding

    佐々木 朋裕

    軽金属溶接 = Journal of light metal welding : 軽金属溶接協会誌   61 ( 2 )   56 - 60   2023.2

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  • 超音波接合—Ultrasonic Bonding—創立60周年記念号 ; 溶接・接合技術の展望

    佐々木 朋裕

    軽金属溶接 = Journal of light metal welding : 軽金属溶接協会誌   60 ( 10 )   488 - 492   2022.10

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  • Field theory of deformation and fracture applied to fatigue fracture

    S. Yoshida, N. Fujishima, T. Sasaki

    AIP Conference Proceedings   2522   2022.9

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    The physical process that underlies the transition from fatigue deformation to fatigue fracture is considered based on the concept of a recent comprehensive theory of deformation and fracture. A typical low-frequency cyclic loading test has been conducted for a thin aluminum plate specimen with the use of an optical interferometric technique to monitor the two-dimensional profile of the displacement field. A numerical model has been constructed to solve the governing equation derived from the field theory. Numerical analyses have been made under various scenarios to assimilate the spatiotemporal behaviors to the corresponding experimental results. This study has found (a) the loss of Poisson's effect along a boundary of specimen initiates the transition to fracture, (b) reduction in the shear modulus accelerates the transition process leading to temporal instability of the displacement field. This temporal instability causes the displacement to grow with time at some location of the specimen. This mechanism may be the direct cause of the generation of material discontinuity, which leads to a macroscopic crack.

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  • In Vivo Assessment of Stiffness of Anterior Oblique Bundle of Ulnar Collateral Ligament Using Ultrasound Elastography

    菅原拓也, 坂本信, 森清友亮, 小林公一, 高根沢佑斗, 佐々木朋裕, 平元和彦

    日本機械学会M&M材料力学カンファレンス(CD-ROM)   2022   2022

  • Measurement of Stiffness of Supraspinatus Tendon Using Ultrasound Elastography

    太田航介, 坂本信, 森清友亮, 小林公一, 高根沢佑斗, 佐々木朋裕, 平元和彦

    日本機械学会M&M材料力学カンファレンス(CD-ROM)   2022   2022

  • Observation of Bubble Behavior in EDM with Ultrasonic Vibration

    Wang Chenxue, Tomohiro Sasaki, Atsutoshi Hirao

    Procedia CIRP   113   267 - 272   2022

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    In electric discharge drilling the machining speed gradually slows down, when the aspect ratio exceeds 5 (L/D=5). As a solution, the Z-axis of the EDM machine on the market is equipped with a jump function. This function effectively removes machining debris and air bubbles. Also, both pipe electrodes and electrodes with special holes are commercially available. The machining fluid is ejected or sucked from the pipe electrode to remove machining debris and air bubbles between the work gap. Therefore, the working gap is always a clean dielectric working fluid, and as a result, the machining speed does not decrease. However, there are cases in which these functions and pipe electrodes cannot be used. To solve these problems, ultrasonic vibration was applied to the electrodes and dielectric working fluid. It has been reported that EDM with ultrasonic vibration affects machining speed. However, the type of phenomenon that occurs during this process has not been reported. In deep hole drilling by EDM, ultrasonic vibration was applied to the electrodes and dielectric working fluid, and the phenomenon at the side working gap was observed using a high-speed microscope. It was confirmed that the air bubbles existing between the side working gap were more effectively removed by applying ultrasonic vibration. If ultrasonic vibration is not applied, air bubbles coalesce. However, it was confirmed that the air bubbles were not united by applying ultrasonic vibration.

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  • Microstructure control of material surface by ultrasonic friction

    小林重昭, 矢口孝祐, 佐々木朋裕

    足利大学総合研究センター年報   ( 22 )   2021

  • Diagnosis of Deformation Stages with Optical Interferometric Technique and Comprehensive Theory of Deformation and Fracture

    Sanichiro Yoshida, Tomohiro Sasaki

    Conference Proceedings of the Society for Experimental Mechanics Series   1 - 6   2021

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    A method to diagnose the stages of deformation nondestructively, quickly and as full-field information is discussed. In-plane sensitive Electronic Speckle-Pattern Interferometry is used in the subtraction mode to form the fringe pattern representing the differential displacement occurring during a short-time interval. The dark fringes in a fringe pattern exhibit the contours of the differential displacement field. The interferometer keeps forming such fringe patterns continuously. The change in the fringe pattern with the development of the deformation is interpreted based on a field theory of deformation and fracture. Based on a fundamental principle of physics, this theory describes all stages of deformation and fracture on the same theoretical basis. It does not need to use phenomenology or empirical formulation of the phenomenon. The transition from one stage to another, e.g., the elastic to plastic stage or the plastic to fracturing stage, of given deformation is diagnosed based on specific features of the fringe patterns and the field theoretical interpretation of the features. The transition from the elastic to plastic stage is characterized by the generation of shear instability that triggers the initiation of a large-scale rotation wave. The transition from the plastic to fracturing stage is characterized by the immobility of the rotation wave that causes the generation of material discontinuity.

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  • 2017 Trend of Welding & Joining in Japan

    JOURNAL OF THE JAPAN WELDING SOCIETY   87 ( 5 )   388 - 394   2018

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    Language:Japanese   Publisher:JAPAN WELDING SOCIETY  

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  • Optical analysis of residual stress with minimum invasion

    Sanichiro Yoshida, Fumiya Miura, Tomohiro Sasaki, Daniel Didie, Shahab Rouhi

    Conference Proceedings of the Society for Experimental Mechanics Series   8   65 - 72   2018

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    Electronic Speckle-Pattern Interferometry (ESPI) has been applied to analyze welding-induced residual stresses. A tensile load is applied to a butt-welded aluminum alloy specimen (tungsten arc bead-on-plate welding on a 100 × 20 mm plate of 5 mm thick) at loading levels up to 20 % of the yield stress, and the acceleration field is evaluated from subtraction of the displacement fields taken in two consecutive time steps. Based on our previously proposed algorithm, the residual stress is estimated from the acceleration field. The resultant residual stress data are compared with experimental results for the same welded specimen based on acoustoelasticity and X-ray diffractometry. Numerical analysis based on Finite Element Modeling has also been conducted. The residual stress data resulting from all the four methods agree with one another, commonly exhibiting the generally accepted concepts that thermal expansion causes tensile residual stress along the weld line and that the effect is greater at the ending side of butt-welding than starting side. The maximum tensile residual stress along the weld line is estimated to be 76.9 ± 12.8 MPa.

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  • Fatigue analysis of 7075 aluminum alloy by optoacoustic method

    Tomohiro Sasaki, Hiroshi Ono, Sanichiro Yoshida, Shuich Sakamoto

    Conference Proceedings of the Society for Experimental Mechanics Series   3   7 - 14   2018

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    The influence of fatigue damage on the elastic response of AA7075 aluminum alloy was investigated through a combination of optical and acoustical experiments. Specimens were previously subjected to fatigue cyclic loads at various fatigue levels within the fatigue life. Macroscopic deformation process under a certain load below the yield point (elastic region) for the pre-fatigued specimen was visualized by electronic speckle pattern interferometry (ESPI). At the same time, the acoustic velocities of vertical and shear waves propagating in the fatigued specimen were measured using an ultrasonic probe. The acoustic analysis showed the following change in residual stress by the fatigue cyclic load; an increase in compressive residual stress with the number of pre-fatigue cycles (NP) below 103, and relaxation of the residual stress NP over 103. The visualization using ESPI demonstrated that the strain heterogeneity in the macroscopic elastic regime was enhanced with increase of the pre-fatigue cycle. The correlation between the optical and the acoustical measurement results is discussed based on the change in the residual stress, localized plastic deformation, and the crack initiation.

    DOI: 10.1007/978-3-319-63028-1_2

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  • 2E10 Proactive guidance and tutoring by class supervisors to prevent grade retentions

    SAKAMOTO Shuichi, TSUKIYAMA Yosuke, SATO Takashi, SASAKI Tomohiro

    Proceedings of Annual Conference of Japanese Society for Engineering Education   2017 ( 0 )   290 - 291   2017

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    DOI: 10.20549/jseeja.2017.0_290

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  • Student's International Activities in Two Decades in Faculty of Engineering, Niigata University

    JSEE Annual Conference International Session proceedings : international cooperation in engineering education   31 - 34   2017

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  • Dynamic deformation with static load

    S. Yoshida, H. Ono, T. Sasaki, M. Usui

    Conference Proceedings of the Society for Experimental Mechanics Series   3   35 - 40   2017

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    We conduct a series of tensile analyses on metal-plate specimens to investigate the relation between the fatigue level and the material’s response to external loads. We use Electronic Speckle-Pattern Interferometery (ESPI) to measures the in-plane displacement, and an acoustic transducer to assess the elastic modulus of the specimen via acoustic velocity measurement at various stress levels. We apply a tensile load at a constant pulling rate up to a certain stress level substantially lower than the yield stress, and analyze the strain field obtained with the ESPI setup at each time step. At the same time, we measure the acoustic velocity at various tensile stress levels. We have found repeatedly in the experiment on an aluminum-alloy specimen that (a) the strain field changes over several seconds after the tensile machine stops pulling, and (b) the acoustic velocity at the same point of the specimen considerably varies from measurement to measurement at the same stress level. These observations indicate that the specimen is deformed even if the crosshead of the tensile machine is stationary. This mysterious phenomenon is consistent with the observation made by Pappalettera et al. in their fatigue analysis that the acoustic emissions, which normally stops when the fatigue reaches a certain level, resumes if the specimen is dismounted from the test machine and remounted for continuation of the test.

    DOI: 10.1007/978-3-319-41600-7_3

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  • Near weld stress analysis with optical and acoustic methods

    Sanichiro Yoshida, Tomohiro Sasaki, Masaru Usui, Shuuichi Sakamoto, Ik Keun Park, Hyunchul Jung, Kyeongsuk Kim

    Conference Proceedings of the Society for Experimental Mechanics Series   9   119 - 127   2016

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    Residual stress induced by brazing and bead welding have been analyzed based on acousto-elasticity and optical interferometry. Acousto-elasticity is to probe compressive or tensile residual stresses from acoustic velocity measurements and optical interferometry is to measure strain induced by an external tensile load. It has been theorized that a compressive residual stress increases the elastic modulus and that an external tensile stress reduces the increase in the elastic modulus. From the tensile stress that brings back the elastic modulus to the nominal value, the residual stress can be estimated. Compressive residual stresses have been estimated in this fashion for a butt-brazed and a butt-bead-welded steel specimens to be of the order of 5 MPa and 50 MPa respectively.

    DOI: 10.1007/978-3-319-21765-9_16

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  • Fatigue damage analysis of aluminum alloy by ESPI

    Tomohiro Sasaki, Shun Hasegawa, Sanichiro Yoshida

    Conference Proceedings of the Society for Experimental Mechanics Series   9   147 - 154   2016

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    In this study, Electronic Speckle Pattern Interferometry (ESPI) and acoustic microscopy were applied to analysis of the fatigue of aluminum alloy. Effect of fatigue damage on the macroscopic deformation behavior during a tensile test has been analyzed with the interferometric fringes. Resultant fringe pattern showed that the elastic compliance in the damaged area increased as the fatigue cycle before the tensile test (Pre-fatigue cycle) increased, resulting in the occurrence of strain localization. In order to know the relation of between the deformation behavior and the microstructural change of the specimen, the acoustic property on the surface has been investigated by a scanning acoustic microscope. It was found that the surface acoustic velocity in the load direction in the pre-fatigue test increased with increasing the pre-fatigue cycle. The results have been discussed based on the fatigue stages of the change in residual stress, local plastic deformation, and the crack initiation.

    DOI: 10.1007/978-3-319-21765-9_19

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  • Effect of horn tip geometry on ultrasonic cavitation peening

    Tomohiro Sasaki, Kento Yoshida, Masayuki Nakagawa, Sanichiro Yoshida

    Conference Proceedings of the Society for Experimental Mechanics Series   9   139 - 146   2016

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    The ultrasonic horns with cylindrical concave surfaces (concaved horn) have been designed and the effect of the concave on cavitation bubbles generation in water has been investigated. High speed camera observation was made on the vibrating horn tip in water and the generation behavior and the impact force of the cavitation bubbles were investigated. In the measurement of impact force, load vibration occurred as the cavitation bubbles collapsed, and peak frequencies were observed at the vibratory frequency of the horn and its harmonic frequency. The impact force was evaluated based on the above peak frequency. The result showed that the concaved horn provide the higher impact force compared to the horn without the concave. Frequency analysis of the load vibration showed that the concaved horn enhanced the generation of cavitation bubbles in the number. The distribution of cavitation bubbles on the horn-tip was evaluated using high-speed image. It was confirmed that the cavitation bubbles flow was effectively converged to the center of concave.

    DOI: 10.1007/978-3-319-21765-9_18

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  • Discussion about approving credits in engineering field between Germany and Japan-Globalization of engineering education-

    佐藤孝, 坂本秀一, 清水忠明, 岡徹雄, 田邊裕治, 後藤康志, 佐々木朋裕, 鈴木孝昌

    電気学会教育フロンティア研究会資料   FIE-15 ( 11-22 )   2015

  • Analysis of fatigue of metals by electronic speckle pattern interferometry

    Shun Hasegawa, Tomohiro Sasaki, Sanichiro Yoshida, Seth L. Hebert

    Conference Proceedings of the Society for Experimental Mechanics Series   3B   127 - 134   2015

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    Electronic Speckle Pattern Interferometry (ESPI) was applied to analysis of the fatigue of metals. The deformation behavior of stainless steel sheet specimen during high-cyclic fatigue tests was dynamically observed by ESPI. The effect of fatigue progress on the deformation behaviors was discussed by evaluating the change in the ESPI fringe pattern focusing on the fatigue stages of crack initiation and crack propagation. The deformation behavior observed in the fatigue test was changed due to the occurrence of crack, and this phenomenon was observed as the fringe concentration around the tip of crack. In addition, static tensile tests with ESPI were performed for specimens which were previously subjected to the fatigue cycle within the fatigue life. The effect of fatigue damage appeared in the deformation behavior near the yielding; the strain concentration behavior caused by local plastic deformation changed depending on the fatigue stage. It was found that the previous cyclic load promotes the local plastic deformation in the static tensile test.

    DOI: 10.1007/978-3-319-06986-9_13

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  • Observation of grain-size effect in serration of aluminum alloy

    Tomohiro Sasaki, Tatsuya Nakamura, Sanichiro Yoshida

    Conference Proceedings of the Society for Experimental Mechanics Series   3B   109 - 115   2015

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    Serration phenomena of AA5083 alloys with various crystal grain sizes during tensile tests were visualized using Electronic Speckle Pattern Interferometry. The behavior of deformation band during the plastic deformation associated with the serration was investigated by a dynamic observation of the images of displacement contours. The characteristic in the serrated curve varied depending on the grain size of specimen and the applied total strain at which the deformation band appeared. The occurrence and propagation processes of the deformation band observed in the displacement contours were investigated being compared with the serrated curve in the load. The correlation between the band propagation and the serrated curve, and the difference in the behavior of band propagation by the grain size were discussed based on the variations in the magnitude of the load drop and the velocity of the moving deformation band.

    DOI: 10.1007/978-3-319-06986-9_11

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  • Stress analysis on welded specimen with multiple methods

    Sanichiro Yoshida, Tomohiro Sasaki, Sean Craft, Masaru Usui, Jeremy Haase, Tyler Becker, Ik Keun Park

    Conference Proceedings of the Society for Experimental Mechanics Series   3B   143 - 152   2015

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    Effects of the thermal stress due to welding on the mechanical property of the welded work are analyzed with multiple methods. Strain gauges and an acoustic microscope are used to measure the residual stress, and electronic speckle pattern interferometry (ESPI) is used to analyze the response of the welded wok to external force. A tensile load is applied to butt-welded, thin-plate steel specimens, and the resultant strain field is analyzed with the ESPI. Comparison is made with the case of a non-welded specimen of the same material and dimensions. The analyses indicate that the residual stress due to welding makes the normal strain due to the external tensile load asymmetric. The asymmetry enhances shear and rotational modes of deformation, generating stress concentration at a point away from the weld where the residual stress is substantially negligible.

    DOI: 10.1007/978-3-319-06986-9_15

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  • Analysis of Relative Motion in Ultrasonic Welding

    SASAKI Tomohiro

    JOURNAL OF THE JAPAN WELDING SOCIETY   83 ( 3 )   204 - 208   2014

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    Language:Japanese   Publisher:JAPAN WELDING SOCIETY  

    DOI: 10.2207/jjws.83.204

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  • Machinability of Intermetallic Compound Fe_3Al(Processing of advanced material)

    SASAKI Tomohiro, YAKOU Takao

    Proceedings of International Conference on Leading Edge Manufacturing in 21st century : LEM21   2005 ( 3 )   1075 - 1079   2005.10

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    Language:English   Publisher:The Japan Society of Mechanical Engineers  

    The intermetallic compound Fe_3Al was processed by a reactive sintering process, and its machinability was investigated using dry turning. In cutting Fe_3Al with a cemented carbide tool, the tool life was approximately one tenth that of cutting carbon tool steel SK3 because of intense flank wear. The tool life for cutting Fe_3Al using the cemented carbide P20 tool was longer than for cemented carbide K10, and a cermet tool reached its tool life limit by chipping for the whole cutting speed range measured. The roughness of the machined surface of Fe_3Al cut using a cemented carbide tool was much smaller than for SK3. However, for cutting using the cermet tool, the roughness showed a sharp rise due to chipping. It was found that tool wear could be attributed to the removal of reinforcement particles. The cemented carbide P20 is suitable for cutting Fe_3Al, and further, highly accurate cutting is possible for Fe_3Al because of the good surface finish.

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Presentations

  • Dynamics of Deformation-to-Fracture Transition Based on Wave Theory

    Sanichiro Yoshida, David R. Didie, Tomohiro Sasaki, Shun Ashina, Shun Takahashi

    Conference Proceedings of the Society for Experimental Mechanics Series  2020 

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    Event date: 2020

    © Society for Experimental Mechanics, Inc. 2020. This paper discusses fracture from the viewpoint of wave dynamics derived from a recent field theory. Based on a fundamental physical principle, the field theory describes deformation and fracture on the same basis. It characterizes deformation as a wave phenomenon where the spatiotemporal oscillatory behavior of the displacement field initiated by an external load is transferred through the material as a sinusoidal wave carrying the stress energy. Fracture is characterized as the final stage of deformation where the wave becomes solitary representing strain concentration and stops carrying the stress energy. Fracture always occurs along the strain concentration. The transitional behavior of the wave dynamics can be visualized as a change in the optical interferometric fringe pattern generated by the optical technique known as the Electronic Speckle-Pattern interferometry. Finite element analysis has been conducted to explain the experimentally observed behaviors and explore the mechanism of transition from to fracture.

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  • Visualization of Fatigue deformation behaviour using Electronic Speckle Pattern Interferometry

    TAKASAWA Keita, SASAKI Tomohiro, NAGAI Tatsuya

    The Proceedings of Conference of Hokuriku-Shinetsu Branch  2019  The Japan Society of Mechanical Engineers

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    Event date: 2019

    Language:Japanese  

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  • Analysis of deformation behavior of aluminum plate in ultrasonic bonding

    OIKAWA Shota, SASAKI Tomohiro, DOI Yuhei, KIM Taewon, ARIMOTO Keisuke

    The Proceedings of Conference of Hokuriku-Shinetsu Branch  2019  The Japan Society of Mechanical Engineers

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    Event date: 2019

    Language:Japanese  

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  • Influence of relative motion on ultrasonic bonding of copper and aluminum

    SASAKI Tomohiro, SIOZAWA Kazuki, NISIYAMA Tadahiro

    The Proceedings of Conference of Hokuriku-Shinetsu Branch  2019  The Japan Society of Mechanical Engineers

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    Event date: 2019

    Language:Japanese  

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  • Heat Deformation analysis of the Gas Pressure Welding using Finite Element Model

    ITO Hajime, YAMAMOTO Ryu-ich, SASAKI Tomohiro

    Preprints of the National Meeting of JWS  2019  JAPAN WELDING SOCIETY

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    Event date: 2019

    Language:Japanese  

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  • Analysis of friction behavior in ultrasonic bonding

    sasaki tomohiro, Arimoto Keisuke, Doi Yuhei, KiM Taewon

    Preprints of the National Meeting of JWS  2018  JAPAN WELDING SOCIETY

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    Event date: 2018

    Language:Japanese  

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  • Fatigue analysis of 7075 aluminum alloy by optoacoustic method

    Tomohiro Sasaki, Hiroshi Ono, Sanichiro Yoshida, Shuich Sakamoto

    Conference Proceedings of the Society for Experimental Mechanics Series  2018 

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    Event date: 2018

    © 2018, The Society for Experimental Mechanics, Inc. The influence of fatigue damage on the elastic response of AA7075 aluminum alloy was investigated through a combination of optical and acoustical experiments. Specimens were previously subjected to fatigue cyclic loads at various fatigue levels within the fatigue life. Macroscopic deformation process under a certain load below the yield point (elastic region) for the pre-fatigued specimen was visualized by electronic speckle pattern interferometry (ESPI). At the same time, the acoustic velocities of vertical and shear waves propagating in the fatigued specimen were measured using an ultrasonic probe. The acoustic analysis showed the following change in residual stress by the fatigue cyclic load; an increase in compressive residual stress with the number of pre-fatigue cycles (NP) below 103, and relaxation of the residual stress NP over 103. The visualization using ESPI demonstrated that the strain heterogeneity in the macroscopic elastic regime was enhanced with increase of the pre-fatigue cycle. The correlation between the optical and the acoustical measurement results is discussed based on the change in the residual stress, localized plastic deformation, and the crack initiation.

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  • Optical analysis of residual stress with minimum invasion

    Sanichiro Yoshida, Fumiya Miura, Tomohiro Sasaki, Daniel Didie, Shahab Rouhi

    Conference Proceedings of the Society for Experimental Mechanics Series  2018 

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    Event date: 2018

    © 2018, The Society for Experimental Mechanics, Inc. Electronic Speckle-Pattern Interferometry (ESPI) has been applied to analyze welding-induced residual stresses. A tensile load is applied to a butt-welded aluminum alloy specimen (tungsten arc bead-on-plate welding on a 100 × 20 mm plate of 5 mm thick) at loading levels up to 20 % of the yield stress, and the acceleration field is evaluated from subtraction of the displacement fields taken in two consecutive time steps. Based on our previously proposed algorithm, the residual stress is estimated from the acceleration field. The resultant residual stress data are compared with experimental results for the same welded specimen based on acoustoelasticity and X-ray diffractometry. Numerical analysis based on Finite Element Modeling has also been conducted. The residual stress data resulting from all the four methods agree with one another, commonly exhibiting the generally accepted concepts that thermal expansion causes tensile residual stress along the weld line and that the effect is greater at the ending side of butt-welding than starting side. The maximum tensile residual stress along the weld line is estimated to be 76.9 ± 12.8 MPa.

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  • Effect of tool geometry in ultrasonic bonding of multilayered foils

    ARIMOTO Keisuke, SASAKI Tomohiro, DOI Yuhei, KIM Taewon

    The Proceedings of Conference of Hokuriku-Shinetsu Branch  2018  The Japan Society of Mechanical Engineers

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    Event date: 2018

    Language:Japanese  

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  • Dynamic deformation with static load

    S. Yoshida, H. Ono, T. Sasaki, M. Usui

    Conference Proceedings of the Society for Experimental Mechanics Series  2017 

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    Event date: 2017

    © The Society for Experimental Mechanics, Inc. 2017. We conduct a series of tensile analyses on metal-plate specimens to investigate the relation between the fatigue level and the material’s response to external loads. We use Electronic Speckle-Pattern Interferometery (ESPI) to measures the in-plane displacement, and an acoustic transducer to assess the elastic modulus of the specimen via acoustic velocity measurement at various stress levels. We apply a tensile load at a constant pulling rate up to a certain stress level substantially lower than the yield stress, and analyze the strain field obtained with the ESPI setup at each time step. At the same time, we measure the acoustic velocity at various tensile stress levels. We have found repeatedly in the experiment on an aluminum-alloy specimen that (a) the strain field changes over several seconds after the tensile machine stops pulling, and (b) the acoustic velocity at the same point of the specimen considerably varies from measurement to measurement at the same stress level. These observations indicate that the specimen is deformed even if the crosshead of the tensile machine is stationary. This mysterious phenomenon is consistent with the observation made by Pappalettera et al. in their fatigue analysis that the acoustic emissions, which normally stops when the fatigue reaches a certain level, resumes if the specimen is dismounted from the test machine and remounted for continuation of the test.

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  • 2E10 Proactive guidance and tutoring by class supervisors to prevent grade retentions

    SAKAMOTO Shuichi, TSUKIYAMA Yosuke, SATO Takashi, SASAKI Tomohiro

    Proceedings of Annual Conference of Japanese Society for Engineering Education  2017  Japanese Society for Engineering Education

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    Event date: 2017

    Language:Japanese  

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  • 706 Brazing of TiAl(γ) based alloy

    FUTA Korenori, SASAKI Tomohiro

    The Proceedings of Conference of Hokuriku-Shinetsu Branch  2016  The Japan Society of Mechanical Engineers

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    Event date: 2016

    Language:Japanese  

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  • Mechanical properties and interfacial phenomena in ultrasonic welding of Al alloy

    Fujii Hiromichi, Ogura Tomo, Saito Shinya, Sasaki Tomohiro, Osada Tomoji, Sugiyama Yoshitaka, Hamada Kensuke, Maeda Masakatsu, Yano Kimiya

    Preprints of the National Meeting of JWS  2016  JAPAN WELDING SOCIETY

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    Event date: 2016

    Language:Japanese  

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  • 701 Ultrasonic spot welding of 5000 series Aluminum alloy and Copper sheets

    NAKAMURA Asuka, SASAKI Tomohiro

    The Proceedings of Conference of Hokuriku-Shinetsu Branch  2016  The Japan Society of Mechanical Engineers

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    Event date: 2016

    Language:Japanese  

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  • Effect of Horn Tip Geometry on Ultrasonic Cavitation Peening

    Tomohiro Sasaki, Kento Yoshida, Masayuki Nakagawa, Sanichiro Yoshida

    RESIDUAL STRESS, THERMOMECHANICS & INFRARED IMAGING, HYBRID TECHNIQUES AND INVERSE PROBLEMS, VOL 9  2016  SPRINGER

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    Event date: 2016

    Language:English  

    The ultrasonic horns with cylindrical concave surfaces (concaved horn) have been designed and the effect of the concave on cavitation bubbles generation in water has been investigated. High speed camera observation was made on the vibrating horn tip in water and the generation behavior and the impact force of the cavitation bubbles were investigated. In the measurement of impact force, load vibration occurred as the cavitation bubbles collapsed, and peak frequencies were observed at the vibratory frequency of the horn and its harmonic frequency. The impact force was evaluated based on the above peak frequency. The result showed that the concaved horn provide the higher impact force compared to the horn without the concave. Frequency analysis of the load vibration showed that the concaved horn enhanced the generation of cavitation bubbles in the number. The distribution of cavitation bubbles on the horn-tip was evaluated using high-speed image. It was confirmed that the cavitation bubbles flow was effectively converged to the center of concave.

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  • Growth of bonded region in ultrasonic bonding of Aluminum alloy

    Sasaki Tomohiro, Chiyozawa Takuya, Kamimura Takumi, Miyazaki Shuhei

    Preprints of the National Meeting of JWS  2016  JAPAN WELDING SOCIETY

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    Event date: 2016

    Language:Japanese  

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  • Fatigue damage analysis of aluminum alloy by ESPI

    Tomohiro Sasaki, Shun Hasegawa, Sanichiro Yoshida

    Conference Proceedings of the Society for Experimental Mechanics Series  2016  SPRINGER

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    Event date: 2016

    Language:English  

    © The Society for Experimental Mechanics, Inc. 2016. In this study, Electronic Speckle Pattern Interferometry (ESPI) and acoustic microscopy were applied to analysis of the fatigue of aluminum alloy. Effect of fatigue damage on the macroscopic deformation behavior during a tensile test has been analyzed with the interferometric fringes. Resultant fringe pattern showed that the elastic compliance in the damaged area increased as the fatigue cycle before the tensile test (Pre-fatigue cycle) increased, resulting in the occurrence of strain localization. In order to know the relation of between the deformation behavior and the microstructural change of the specimen, the acoustic property on the surface has been investigated by a scanning acoustic microscope. It was found that the surface acoustic velocity in the load direction in the pre-fatigue test increased with increasing the pre-fatigue cycle. The results have been discussed based on the fatigue stages of the change in residual stress, local plastic deformation, and the crack initiation.

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  • Effect of horn tip geometry on ultrasonic cavitation peening

    Tomohiro Sasaki, Kento Yoshida, Masayuki Nakagawa, Sanichiro Yoshida

    Conference Proceedings of the Society for Experimental Mechanics Series  2016  SPRINGER

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    Event date: 2016

    Language:English  

    © The Society for Experimental Mechanics, Inc. 2016. The ultrasonic horns with cylindrical concave surfaces (concaved horn) have been designed and the effect of the concave on cavitation bubbles generation in water has been investigated. High speed camera observation was made on the vibrating horn tip in water and the generation behavior and the impact force of the cavitation bubbles were investigated. In the measurement of impact force, load vibration occurred as the cavitation bubbles collapsed, and peak frequencies were observed at the vibratory frequency of the horn and its harmonic frequency. The impact force was evaluated based on the above peak frequency. The result showed that the concaved horn provide the higher impact force compared to the horn without the concave. Frequency analysis of the load vibration showed that the concaved horn enhanced the generation of cavitation bubbles in the number. The distribution of cavitation bubbles on the horn-tip was evaluated using high-speed image. It was confirmed that the cavitation bubbles flow was effectively converged to the center of concave.

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  • Near weld stress analysis with optical and acoustic methods

    Sanichiro Yoshida, Tomohiro Sasaki, Masaru Usui, Shuuichi Sakamoto, Ik Keun Park, Hyunchul Jung, Kyeongsuk Kim

    Conference Proceedings of the Society for Experimental Mechanics Series  2016  SPRINGER

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    Event date: 2016

    Language:English  

    © The Society for Experimental Mechanics, Inc. 2016. Residual stress induced by brazing and bead welding have been analyzed based on acousto-elasticity and optical interferometry. Acousto-elasticity is to probe compressive or tensile residual stresses from acoustic velocity measurements and optical interferometry is to measure strain induced by an external tensile load. It has been theorized that a compressive residual stress increases the elastic modulus and that an external tensile stress reduces the increase in the elastic modulus. From the tensile stress that brings back the elastic modulus to the nominal value, the residual stress can be estimated. Compressive residual stresses have been estimated in this fashion for a butt-brazed and a butt-bead-welded steel specimens to be of the order of 5 MPa and 50 MPa respectively.

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  • Field theoretical description of shear bands

    Sanichiro Yoshida, Tomohiro Sasaki

    Conference Proceedings of the Society for Experimental Mechanics Series  2016  SPRINGER

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    Event date: 2016

    Language:English  

    © The Society for Experimental Mechanics, Inc. 2016. Spatiotemporal behaviors of the shear band have been analyzed. Based on a recent field theory of deformation and fracture, it has been hypothesized that (a) a shear band is formed along the boundary of opposite rotational displacements of a specimen, (b) When the propagation velocity of movable dislocations along the front of a shear band is higher than the phase velocity of the rotation wave the shear band appears continuously whereas when the velocity of the dislocations is lower than the rotation wave the shear band travels at the same velocity as the rotational wave appearing intermittently. Electronic-Speckle-Pattern Interferometric setup has been used to monitor the formation and movement of shear bands under various tensile strain rates. The observed spatiotemporal characteristics of the shear bands have been found to support the above hypotheses.

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  • Near Weld Stress Analysis with Optical and Acoustic Methods

    Sanichiro Yoshida, Tomohiro Sasaki, Masaru Usui, Shuuichi Sakamoto, Ik-keun Park, Hyunchul Jung, Kyeongsuk Kim

    RESIDUAL STRESS, THERMOMECHANICS & INFRARED IMAGING, HYBRID TECHNIQUES AND INVERSE PROBLEMS, VOL 9  2016  SPRINGER

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    Event date: 2016

    Language:English  

    Residual stress induced by brazing and bead welding have been analyzed based on acousto-elasticity and optical interferometry. Acousto-elasticity is to probe compressive or tensile residual stresses from acoustic velocity measurements and optical interferometry is to measure strain induced by an external tensile load. It has been theorized that a compressive residual stress increases the elastic modulus and that an external tensile stress reduces the increase in the elastic modulus. From the tensile stress that brings back the elastic modulus to the nominal value, the residual stress can be estimated. Compressive residual stresses have been estimated in this fashion for a butt-brazed and a butt-bead-welded steel specimens to be of the order of 5 MPa and 50 MPa respectively.

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  • Field Theoretical Description of Shear Bands

    Sanichiro Yoshida, Tomohiro Sasaki

    FRACTURE, FATIGUE, FAILURE AND DAMAGE EVOLUTION, VOL 8  2016  SPRINGER

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    Event date: 2016

    Language:English  

    Spatiotemporal behaviors of the shear band have been analyzed. Based on a recent field theory of deformation and fracture, it has been hypothesized that (a) a shear band is formed along the boundary of opposite rotational displacements of a specimen. (b) When the propagation velocity of movable dislocations along the front of a shear band is higher than the phase velocity of the rotation wave the shear band appears continuously whereas when the velocity of the dislocations is lower than the rotation wave the shear band travels at the same velocity as the rotational wave appearing intermittently. Electronic-Speckle-Pattern Interferometric setup has been used to monitor the formation and movement of shear bands under various tensile strain rates. The observed spatiotemporal characteristics of the shear bands have been found to support the above hypotheses.

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  • Fatigue Damage Analysis of Aluminum Alloy by ESPI

    Tomohiro Sasaki, Shun Hasegawa, Sanichiro Yoshida

    RESIDUAL STRESS, THERMOMECHANICS & INFRARED IMAGING, HYBRID TECHNIQUES AND INVERSE PROBLEMS, VOL 9  2016  SPRINGER

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    Event date: 2016

    Language:English  

    In this study, Electronic Speckle Pattern Interferometry (ESPI) and acoustic microscopy were applied to analysis of the fatigue of aluminum alloy. Effect of fatigue damage on the macroscopic deformation behavior during a tensile test has been analyzed with the interferometric fringes. Resultant fringe pattern showed that the elastic compliance in the damaged area increased as the fatigue cycle before the tensile test (Pre-fatigue cycle) increased, resulting in the occurrence of strain localization. In order to know the relation of between the deformation behavior and the microstructural change of the specimen, the acoustic property on the surface has been investigated by a scanning acoustic microscope. It was found that the surface acoustic velocity in the load direction in the pre-fatigue test increased with increasing the pre-fatigue cycle. The results have been discussed based on the fatigue stages of the change in residual stress, local plastic deformation, and the crack initiation.

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  • Spontaneous Recurrence of Deposition and Dissolution of a Solid Layer on a Solution Surface

    Tomohiro Sasaki, Nobuhiko J. Suematsu, Tatsunari Sakurai, Hiroyuki Kitahata

    JOURNAL OF PHYSICAL CHEMISTRY B  2015.7  AMER CHEMICAL SOC

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    Event date: 2015.7

    Language:English  

    We investigated the spontaneous recurrence of deposition and dissolution of camphor layer on the surface of camphor methanol solution. This recurrence is a novel rhythmic process concerned with solid-liquid phase transition. To elucidate the underlying mechanism, we measured the solution temperature at different times, and found that the temperature increased, and decreased repetitively, correlating with the camphor layer's deposition and dissolution. These experimental results show that the solution temperature plays an important role in recurrence of deposition and dissolution.

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  • Analysis of fatigue of metals by electronic speckle pattern interferometry

    Shun Hasegawa, Tomohiro Sasaki, Sanichiro Yoshida, Seth L. Hebert

    Conference Proceedings of the Society for Experimental Mechanics Series  2015  SPRINGER-VERLAG BERLIN

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    Event date: 2015

    Language:English  

    © The Society for Experimental Mechanics, Inc. 2015. Electronic Speckle Pattern Interferometry (ESPI) was applied to analysis of the fatigue of metals. The deformation behavior of stainless steel sheet specimen during high-cyclic fatigue tests was dynamically observed by ESPI. The effect of fatigue progress on the deformation behaviors was discussed by evaluating the change in the ESPI fringe pattern focusing on the fatigue stages of crack initiation and crack propagation. The deformation behavior observed in the fatigue test was changed due to the occurrence of crack, and this phenomenon was observed as the fringe concentration around the tip of crack. In addition, static tensile tests with ESPI were performed for specimens which were previously subjected to the fatigue cycle within the fatigue life. The effect of fatigue damage appeared in the deformation behavior near the yielding; the strain concentration behavior caused by local plastic deformation changed depending on the fatigue stage. It was found that the previous cyclic load promotes the local plastic deformation in the static tensile test.

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  • Observation of grain-size effect in serration of aluminum alloy

    Tomohiro Sasaki, Tatsuya Nakamura, Sanichiro Yoshida

    Conference Proceedings of the Society for Experimental Mechanics Series  2015  SPRINGER-VERLAG BERLIN

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    Event date: 2015

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    © The Society for Experimental Mechanics, Inc. 2015. Serration phenomena of AA5083 alloys with various crystal grain sizes during tensile tests were visualized using Electronic Speckle Pattern Interferometry. The behavior of deformation band during the plastic deformation associated with the serration was investigated by a dynamic observation of the images of displacement contours. The characteristic in the serrated curve varied depending on the grain size of specimen and the applied total strain at which the deformation band appeared. The occurrence and propagation processes of the deformation band observed in the displacement contours were investigated being compared with the serrated curve in the load. The correlation between the band propagation and the serrated curve, and the difference in the behavior of band propagation by the grain size were discussed based on the variations in the magnitude of the load drop and the velocity of the moving deformation band.

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  • Stress analysis on welded specimen with multiple methods

    Sanichiro Yoshida, Tomohiro Sasaki, Sean Craft, Masaru Usui, Jeremy Haase, Tyler Becker, Ik Keun Park

    Conference Proceedings of the Society for Experimental Mechanics Series  2015  SPRINGER-VERLAG BERLIN

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    Event date: 2015

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    © The Society for Experimental Mechanics, Inc. 2015. Effects of the thermal stress due to welding on the mechanical property of the welded work are analyzed with multiple methods. Strain gauges and an acoustic microscope are used to measure the residual stress, and electronic speckle pattern interferometry (ESPI) is used to analyze the response of the welded wok to external force. A tensile load is applied to butt-welded, thin-plate steel specimens, and the resultant strain field is analyzed with the ESPI. Comparison is made with the case of a non-welded specimen of the same material and dimensions. The analyses indicate that the residual stress due to welding makes the normal strain due to the external tensile load asymmetric. The asymmetry enhances shear and rotational modes of deformation, generating stress concentration at a point away from the weld where the residual stress is substantially negligible.

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  • Friction behavior between tool and weld material in ultrasonic welding

    Komiyama Kazuki, Sasaki Tomohiro, Takano Moe

    Preprints of the National Meeting of JWS  2015  JAPAN WELDING SOCIETY

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    Event date: 2015

    Language:Japanese  

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  • Ultrasonic welding process of 6061 aluminum alloy

    Chiyozawa Takuya, Sasaki Tomohiro

    Preprints of the National Meeting of JWS  2015  JAPAN WELDING SOCIETY

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    Event date: 2015

    Language:Japanese  

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  • Observation of Grain-Size Effect in Serration of Aluminum Alloy

    Tomohiro Sasaki, Tatsuya Nakamura, Sanichiro Yoshida

    ADVANCEMENT OF OPTICAL METHODS IN EXPERIMENTAL MECHANICS, VOL 3  2015  SPRINGER-VERLAG BERLIN

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    Event date: 2015

    Language:English  

    Serration phenomena of AA5083 alloys with various crystal grain sizes during tensile tests were visualized using Electronic Speckle Pattern Interferometry. The behavior of deformation band during the plastic deformation associated with the serration was investigated by a dynamic observation of the images of displacement contours. The characteristic in the serrated curve varied depending on the grain size of specimen and the applied total strain at which the deformation band appeared. The occurrence and propagation processes of the deformation band observed in the displacement contours were investigated being compared with the serrated curve in the load. The correlation between the band propagation and the serrated curve, and the difference in the behavior of band propagation by the grain size were discussed based on the variations in the magnitude of the load drop and the velocity of the moving deformation band.

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  • Analysis of stress due to welding based on multiple techniques

    S.Yoshida, T.Becker, D.Didie, C.Delaune, S-H. Oh, M.Usui, T.Sasaki

    Analysis of stress due to welding based on multiple techniques, ICCES’14, (June 2014), Changwon, Korea  2014.6 

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    Event date: 2014.6

    Language:English  

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  • Observation of serrated plastic flow behavior of aluminum alloys by electronic speckle pattern interferometry

    T.Sasaki, T.Nakamura, S.Yoshida

    Analysis of stress due to welding based on multiple techniques, ICCES’14, (June 2014), Changwon, Korea  2014.6 

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    Event date: 2014.6

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  • Effect of relative motion between weld tool and work piece on microstructure of ultrasonically welded joint

    Tomohiro Sasaki, Yusuke Hosokawa

    Materials Science Forum  2014 

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    Event date: 2014

    Language:English  

    Ultrasonic welding is conducted using pure aluminum sheets to investigate effect of the transitional welding processes comprised of three transitional stages on the formation of the weld microstructure. In the first stage of ultrasonic welding, the relative motion mainly occurred between the workpieces, and a partially bonded region was observed in the weld interface. In the second stage, the relative motion at the weld interface was suppressed by the formation of the partially bonded region, while relative motion between the weld tool and the workpiece in contact with the weld tool. The relative motion at the weld tool/workpiece caused weld temperature rise with a penetration the weld tool edge. In the third stage, a plastic deformation zone generated by the relative motion at the weld tool/workpiece spread into the lower side of weld part as the welding time increased. It is proposed that the formation of weld microstructure in ultrasonic welding is attributed to the thermo-mechanically effect of the relative motion of the weld tool and workpiece. © (2014) Trans Tech Publications, Switzerland.

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  • Optical analysis of weld-induced residual stress by electronic speckle-pattern interferometry

    Sean Craft, Saugat Ghimire, Bishwas Ghimire, Sanichiro Yoshida, T. Sasaki

    Conference Proceedings of the Society for Experimental Mechanics Series  2014 

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    Event date: 2014

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    Electronic Speckle-Pattern Interferometry (ESPI) is applied to analysis of residual stress induced by laser welding. A thin plate of stainless-steel is butt-welded to a carbon-steel plate of the same dimension to form a dissimilar-weld specimen. Similarly, a pair of stainless-steel plates and that of carbon-steel plates are respectively butt-welded to each other to form similar-weld specimens. The dimensions of the dissimilar and simlar-weld specimens are all the same. A tensile load is applied to the specimen perpendicular to the weld line and at a constant pulling rate until the stress on the sample is approximately a quarter of the yield stress. The resultant deformation is monitored with an ESPI setup sensitive to the in-plane displacement component parallel to the tensile axis. Interferometric images are formed at a fixed time interval, and fringe patterns representing contours of the in-plane displacement are created by subtracting the image taken at each time step from several time steps after. Resultant fringe patterns show behaviors that can be interpreted as revealing residual stress. © The Society tor Experimental Mechanics, Inc. 2014.

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  • Water cavitation peening by ultrasonic vibration for improvement of fatigue strength of stainless steel sheet

    Tomohiro Sasaki, Shun Hasegawa, Masayuki Nakagawa, Sanichiro Yoshida

    Conference Proceedings of the Society for Experimental Mechanics Series  2014 

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    Event date: 2014

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    Water cavitation peening has been applied to thin sheets of austenitic stainless steel of 0.1 mm in thickness. The influence of cavitation peening on various factors related to the fatigue property of the material has been investigated. It has been found that the fatigue limit is increased by about approximately 10%, while no significant changes in the surface roughness and the microstructure are observed. The residual stress evaluated by Full Width at Half Maximum (FWHM) of X-ray diffraction, and the mean value of micro-hardness on the surface are slightly decreased in the peened specimen. To investigate the origin of increase in fatigue strength, deformation behavior in the tensile test has been measured using electronic speckle pattern interferometry. The optical fringe patterns by ESPI (Electronic Speckle-Pattern Interferometry) during the transitional process from the elastic deformation to the yielding have shown that local plastic deformation due to the strain concentration was suppressed by the cavitation peening. © The Society for Experimental Mechanics, Inc. 2014.

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  • Analysis of Portevin-Le Chatelier effect of Al-Mg alloy by electronic speckle pattern interferometry

    Tatsuya Nakamura, Tomohiro Sasaki, Sanichiro Yoshida

    Conference Proceedings of the Society for Experimental Mechanics Series  2014 

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    Event date: 2014

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    Displacement field in AA5052 alloy during tensile test was visualized using Electronic speckle pattern interferometry. The process of nucleation and propagation of Portevin-Le Chatelier deformation band during the plastic deformation were investigated by a dynamic observation of the images of displacement contours (fringe pattern). Various types of bands were observed depending on the applied strain rate and the total strain at which the deformation band (DB) appeared. The characteristics of nucleation and propagation of DBs were discussed being compared with the serrated curve in the load. Type A and B serration observed at the high strain rate was characterized by local strain in the DB, and it was found that the difference between type A and B arises from the increase in the local strain rate. Deformation band at low strain rate showed complicated change in response to the nucleation and propagation processes. The correlation between the band propagation and the serrated curve was discussed based on the variation in density and velocity of mobile dislocation. © The Society for Experimental Mechanics Inc. 2014.

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  • Effect of tool geometry on microstructure of ultrasonic welded joint

    T.Sasaki, Y. Sakata, Y.Watanabe

    International Symposium on Interfacial Joining and Surface Technology, (Nov.2013), Osaka Japan  2013.10 

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    Event date: 2013.10

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  • Analysis of ultrasonic welding process of aluminum alloy and mild steel sheet

    T.Nagai, T.Sasaki, T.Watanabe

    International Symposium on Interfacial Joining and Surface Technology, (Nov.2013), Osaka Japan  2013.10 

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    Event date: 2013.10

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  • Effect of loading history of aluminum on fringe pattern in electronic speckle pattern interferometry

    Hiroyuki Suzuki, Tomohiro Sasaki, Takehiko Watanabe, Sanichiro Yoshida

    Conference Proceedings of the Society for Experimental Mechanics Series  2013 

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    Event date: 2013

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    Deformation behaviors of aluminum sheet that experienced deformation were measured using electronic speckle pattern interferometry method. The specimens with notch were tensile loaded to various load levels and reloaded to the same level. In order to reveal loading history of material, the changes in two-dimensional displacement fields during the reloading were observed as interferometric fringe patterns. The deformation behavior observed in the tensile test generally consisted of the three different stages of macroscopically elastic deformation, local plastic deformation in a small region near the notch tip, and large scale plastic deformation with formation of plastic region around the notch. The transition process of these stages changed depending on the load level in which the specimen experienced in past. Consequently, the difference in the deformation behavior in the reloading was observed as the changes in fringe patterns. The deformation behavior in the reloading was analyzed with the observed fringe patterns. © The Society for Experimental Mechanics, Inc. 2013.

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  • Evaluation of dynamic deformation behavior of aluminum alloy by electronic speckle pattern interferometry

    Tomohiro Sasaki, Hiroyuki Suzuki, Sanichiro Yoshida

    Conference Proceedings of the Society for Experimental Mechanics Series  2013 

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    Event date: 2013

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    Two-dimensional displacement field in Al-Zn-Mg-Cu alloy during tensile test was measured using an electronic speckle pattern interferometric method. The specimens prepared were aged to a peak hardness and over-aged, and the images of displacement contours consisted of fringes (fringe pattern) in the elastic/plastic deformation were compared. The fringe patterns were classified by the deformation process. In elastic region, the fringe pattern of longitudinal displacement consisted of straight line with equal intervals. The fringe curved at the onset of yielding, the plastic deformation started with the fringe concentration at the parallel part of specimen. The plastic deformation was characterized as the stress concentration process in the parallel part of specimen. The patterns in the plastic deformation differed depending on the heat treatment condition of specimen. The plastic deformation processes were evaluated by changes in the strain component. In the peak aged alloy, the plastic deformation progressed with macroscopically uniform strain until the necking, while in the over-aged alloy, alloy, the deformation progressed by drifting of deformation band (DB). Portevin-Le Chatelier effect was observed with the occurrence and disappearance of DB. © The Society for Experimental Mechanics, Inc. 2013.

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  • Relationship Between Relative Motion in Ultrasonic Welding and Formation of Weld Microstructure

    Y.Hosokawa, T.Sasaki, T.Watanabe, A.Yanagisawa

    Proceedings of International Conference on Advancese in Materials & Processing Technologies  2012.9 

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    Event date: 2012.9

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  • Effect of Weld Tip Geometry on Ultrasonic Welding of Aluminum Alloy

    Takehiko Watanabe, Kosuke Nishihara, Tomohiro Sasaki

    THERMEC 2009, PTS 1-4  2010  TRANS TECH PUBLICATIONS LTD

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    Event date: 2010

    Language:English  

    Authors ultrasonically welded A6061 aluminum alloy sheet using two types of weld tips with the different contact face geometry, and investigated the effect of the weld tip geometry on the performance and the interface structure of welds. One type of tip has a cylindrical contact face without knurl, which is called C-tip in this study The other type of tip has flat contact face with knurl, which is called K-tip in this study. The strength of the joints welded using C-tip was higher than that welded using K-tip and the C-tip could stably produce the higher strength joint.

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  • Ultrasonic Welding Mild Steel Sheet to Al-Mg Alloy Sheet

    Atsushi Watanabe, Takehiko Watanabe, Tomohiro Sasaki

    THERMEC 2009 SUPPLEMENT  2010  TRANS TECH PUBLICATIONS LTD

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    Event date: 2010

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    Ultrasonic welding between SS400 mild steel sheet and aluminum alloy A5052 sheet containing magnesium was conducted. In this study, authors investigated the influence of ultrasonic welding condition on the mechanical properties and the interface microstructure of a joint, and examined the effect of an insert metal to improve the joint strength. The main results obtained in this study are as follows.It was possible to ultrasonically weld SS400 mild steel sheet and A5052 sheet. When the clamping force was varied keeping the welding time constant for 1s, the joint strength showed the maximum at the clamping force of 588N and it decreased with increasing the clamping force because the frictional action at the interface decreased with it. When the clamping force was kept constant at 588N and the welding time was varied, the joint strength reached the maximum at the welding time of 2.5s, followed by decreasing in the joint strength welded at 3s welding time due to the formation of Fe2Al5 intermetallic compound at the interface. Using insert metal of commercially pure aluminum successfully improved the joint strength and the strength of the joint welded at 3s welding time was about three times larger than that without the insert metal.

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  • Dissociation mechanism of electronically excited CH2X2 (X = Cl, Br) formed by near-resonant neutralization using charge-inversion mass spectrometry

    Shigeo Hayakawa, Tomohiro Sasaki, Hiroshi Matsubara

    CHEMICAL PHYSICS LETTERS  2008.9  ELSEVIER SCIENCE BV

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    Event date: 2008.9

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    The dissociation mechanism of excited CH2X2 (X = Cl, Br) was investigated using charge-inversion mass spectrometry, in which positive ions collide with an alkali metal target to generate neutral fragments, and the negative ions formed from the neutral fragments are mass analyzed. Different relative abundances of the negative ions were observed in the charge- inversion spectra for CH2Cl2 and CH2Br2. The kinetic energy release values calculated from analysis of the peak associated with CHCl2- in the charge-inversion mass spectrum of the parent CH2Cl2+ ion indicate that the excited CH2Cl2 formed by neutralization dissociates spontaneously into CHCl2 + H. (c) 2008 Elsevier B.V. All rights reserved.

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  • Effect of Mg and Si for machined surface during low-speed orthogonal cutting of A6061 alloy

    2008.3 

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    Event date: 2008.3

    Language:Japanese  

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  • Development of High Temperature Diffusion Treatment for Aluminum Coated Steel

    SASAKI Tomohiro, YAKOU Takao

    2008.2 

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    Event date: 2008.2

    Language:Japanese  

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  • 3420 Fundamental Slicing Characteristics of Fe-Al Intermetallic Compounds

    KATTA Hiroki, SAKAMOTO Satoshi, USUKI Hiroshi, MATSUMOTO Akira, YAKOU Takao, SADAKI Tomohiro

    The proceedings of the JSME annual meeting  2008  The Japan Society of Mechanical Engineers

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    Event date: 2008

    Language:Japanese  

    The Fe-Al intermetallic compounds have a high hardness and superior resistance against a wear, a heat and an oxidation. Therefore it is expected that the compounds will be used as a tool material and a high temperature structural material for a chemical plant, a turbine, a catalyst and so on. Although the intermetallic compounds are typically formed by near-net shape methods such as sintering or casting because of their poor ductility and plastic deformability, machining is required as a finishing method to form a highly accurate product. Some studies on the machinability of the intermetallic compounds have been reported so far, which reports about the cutting such as the lathe turning mainly. Additionally, there are few reports about machinability of the single phase. The main purpose of this study is to clarify the fundamental slicing characteristic of the single phase body of the Fe-Al intermetallic compounds. The main results obtained are as follows. The machinability of the Fe-Al intermetallic compounds is inferior comparing with the hard and brittle materials such as Pyrex or polycrystalline silicon, and then the multi-wire saw is available for the high precision slicing.

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  • 3418 Machinability Aluminum Alloy from Viewpoint of Tensile Property and Adhesion

    ITO Tadayuki, YAKOU Takao, SASAKI Tomohiro

    The proceedings of the JSME annual meeting  2008  The Japan Society of Mechanical Engineers

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    Event date: 2008

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    As investigation of the relation between adhesion on rake face of tool and machined surface for some commercial aluminum alloys, the following result was obtained. The adhesion appeared on the rake face has two types, in the former type, adhered material on the rake face was thin and the evaluation of adhesion area varied. In the latter type, adhered material on the rake face was thick and the evaluation of adhesion area was stable. In the case of thin adhesion, the surface roughness after machining Ra has small value and increase with increasing adhesion area A. On the other hand, in the case of thick adhesion, Ra has large value and decrease with increasing A.

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  • 3417 Effect of Si addition for machinability and adhesion of Al-Si alloy

    SHIRATO Kazuya, SASAKI Tomohiro, YAKOU Takao

    The proceedings of the JSME annual meeting  2008  The Japan Society of Mechanical Engineers

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    Event date: 2008

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    Al-Si Alloys which contain 0-2mass%Si were processed and machined by dry cutting in order to clarify effect of solid soluted Si on machinability of Al-Si alloy. In work material containing 0-1.5mass%Si, adhesion stacked on cutting edge widely and the surface roughness was increased with increasing the content of solid soluted Si. On the other hand, in the work material containing above 1.5mass%, adhesion on cutting edge spread thinly compared with other work materials and surface roughness was decreased. Moreover, eutectic Si was confirmed on machined surface in work material containing 2mass%Si. From those result, it was considered that solid soluted Si increased surface roughness.

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  • 3419 Relationship between Composition and Machinability of Fe-Al System Intermetallics

    ITO Yu, SASAKI Tomohiro, YAKOU Takao

    The proceedings of the JSME annual meeting  2008  The Japan Society of Mechanical Engineers

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    Event date: 2008

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    To investigate the relationship between composition and machinability of Fe-Al system intermetallics, orthogonal cutting was performed for some aluminum content of Fe-Al alloy. In the case of small depth of cut, the machined surface of low the aluminum content alloy was smooth, and many cracks were appeared in the high aluminum content alloy. This tendency was more prominent in the case of large depth of cut. Chip shape of the low aluminum content alloy was flow type. However, in the high aluminum content alloy, it was divided into parts finely.

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  • 745 Relationship between Operatability and Ggrip Configuration of Excretion

    YAKOU Takao, SASAKI Tomohiro, YAMAMOTO Keijiro, TAKAHASHI Katsumi

    The Proceedings of the Dynamics & Design Conference  2007  The Japan Society of Mechanical Engineers

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    Event date: 2007

    Language:Japanese  

    Relationship between operatability of excretion support equipment for wheelchair users and grip diameter of controller had been investigated. Length from the controller to the actuator had an optimum value related the length of user's hand. The optimum length in this study was 350mm. Moreover, the diameter of grip had an optimum range from 20mm to 35mm. This diameter range was smaller than that of power grip. It is understood that the operations in this study were precision grip concerned with the fingertrip.

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  • 20418 Elucidation of Deformation and Surface Crack Generation in Layered Material using Electronic Speckle Pattern Interferometry

    ARIKAWA Shuichi, GOMI Kenji, SASAKI Tomohiro, YAKOU Takao, ICHINOSE Kensuke

    The Proceedings of Conference of Kanto Branch  2007  The Japan Society of Mechanical Engineers

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    Event date: 2007

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    The surface of a layered material was observed by electronic speckle pattern interferometry under the tensile test. Characteristics patterns as white points or lines were observed by electronic speckle pattern interferometry with crack generation. The crack generated on the surface was compared with the pattern. the position of the pattern corresponded with the position of the crack which was observed by microscope.

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  • 20406 Effect of Thickness of Fe-Rich Alloyed Layers Formed by High-Temperature Aluminized Steels

    ARIKAWA Shuichi, SASAKI Tomohiro, GOMI Kenji, YAKOU Takao, ICHINOSE Kensuke

    The Proceedings of Conference of Kanto Branch  2007  The Japan Society of Mechanical Engineers

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    Event date: 2007

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    High-temperature aluminaizing which is diffusion process at a temperature higher than 950℃ make a Fe-rich alloy layer. The tensile test was done for the high-temperature aluminized steels which have the Fe-rich alloy of aluminum solid soluted ferrite on the surface of carbon steel. As a result, tensile strength of aluminized steels was 1.4 times of that of the carbon steel.

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  • 744 Fitting sence Evaluation of the Closing Sence of Screw

    YAKOU Takao, SASAKI Tomohiro, YAMAMOTO Keijiro

    The Proceedings of the Dynamics & Design Conference  2007  The Japan Society of Mechanical Engineers

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    Event date: 2007

    Language:Japanese  

    The feeling of a wood-screw tightening using a screw driver has been examined. As a result, The screw driver cam be rotated when the screw driver bit size is smaller than the cross-grove size of screw head. However, the operation time of screw closing become long as those incompatibility degree increases. It has been understood that thess cause are the stability during screw driver operation at the early stage of screw tighening. Moreover, increasing the wood hardness tends to in crease the operation time, fatigue, the feeling of a wood screw tightning and the feeling of grasping.

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  • 413 Effect of eutectic Si and primary Si on machinability of Al-Si alloys

    Nagatsuma Yoshiki, Kamiya Masatsugu, Sasaki Tomohiro, Yakou Takao

    The Proceedings of The Manufacturing & Machine Tool Conference  2006  The Japan Society of Mechanical Engineers

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    Event date: 2006

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    In this report, Al-Si alloys which contain 2-25mass%Si was processed and machined by dry cutting in order to clarify effect of eutectic Si particles and primary Si particles on machinability of Al-Si alloy. The number of chips per unit weight was rapidly increased in machining specimens containing more than 15mass%Si. Moreover, Chip thickness and curl radius decrease with increasing the eutectic Si. It was found that these are due to higher hardness of matrix caused by eutectic Si particles. Therefore, it is considered that the crack of primary Si which act as a nucleus of chip breaking grow up, and thereby the increase of number of chips was promoted.

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  • 639 Relationship between Sensory Evaluation of Temperature Fluctuation and Operation Temperature of TiNi Actuator

    YAKOU Takao, SASAKI Tomohiro, YAMAMOTO Keijiro, SAKAI Naotaka, TAKAGI Nobuaki

    The Proceedings of the Dynamics & Design Conference  2006  The Japan Society of Mechanical Engineers

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    Event date: 2006

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    To obtaion imformation about temperature fluctuation to oparate the TiNi actuator, sensory evaluation tests for temperature fluctuation has been performed. At the leaved parts from the center of the body like finger tips of hand and foot, it was found to be able to endured the wider temperature fluctuation region at lower temperater from the temperature of body than that at higer temperature. In addition,at near parts the center of the body such as arm and leg, it became clear that there was no diffrence in the sensory evaluation value at high temperater and low temperartre compered with the temperature of body.

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  • 207 Effect of two-step diffusion-treatment on formation of alloy layer at steel/aluminum interface

    Kobayashi Shigeaki, Itoi Yuta, Okunuki Takashi, Sasaki Tomohiro, Yakou Takao

    2006 

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  • 414 Influence of Mg_2Si for Machinability of Al-Mg-Si Alloy

    SASAKI Tomohiro, NAGATSUMA Yoshiki, YAKOU Takao

    The Proceedings of The Manufacturing & Machine Tool Conference  2006  The Japan Society of Mechanical Engineers

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    Event date: 2006

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    Machinability of Al-Mg-Si alloy is investigated using an orthogonal cutting test. The yield stress and elongation rose by increasing Mg_2Si content. This tendency was prominent in the aging condition of T6 (Aging at 180℃ after solution heat treatment). On the other hand, the yield stress and elongation increased largely by addition of excess Si in the whole aging condition. The cutting resistance of a material added excess Si (C5) was smallest, and the burr formation at the edge of work was suppressed. In the aging condition of T6, the cutting resistance was large because of large strength of work and thickness of chip. The width of burr decreased by prestraining of 10 percent before machining.

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  • 415 Dominant factor on chip breakability of aluminum alloys

    KAMIYA Masatsugu, SASAKI Tomohiro, YAKOU Takao

    The Proceedings of The Manufacturing & Machine Tool Conference  2006  The Japan Society of Mechanical Engineers

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    Event date: 2006

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    In order to investigate the influence of second-phase particles on chip breakability of aluminum alloys, turning test for various wrought aluminum alloys were carried out with carbide inserts (K10) in dry and wet cutting conditions. In the materials, Al_2Cu, Al_6Mn, Mg_2Si, Al-Fe-Si system compound and eutectic Si were observed as second-phase particles. Chip breakability of materials which containing Al_2Cu or Si as second-phase particles were superior than that of materials with Mg_2Si or Al-Fe-Si system compound. This tendency was more prominent in wet cutting than in dry cutting. The Al_2Cu and Si particles on the machined surface were fractured by cutting tool in machining. It was estimated that those fractured second-phase particles acted as nucleus of chip breaking during machining. Moreover, the increase of the chip breakability in wet cutting was attributable to the promotion of fracture of Al_2Cu and Si particles due to the Rehbinder effect.

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  • 410 Microstructure and Machinability of TiAl based Intermetallic Compound

    SAIKI Kazuki, KOKUTA Kaoru, SASAKI Tomohiro, YAKOKU Takao

    The Proceedings of The Manufacturing & Machine Tool Conference  2006  The Japan Society of Mechanical Engineers

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    Event date: 2006

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    Machinability of Ti-47.7at%Al intermetallic compound having TiAl-Ti_3Al full lamellar structure is investigated by orthogonal cutting test using cemented carbide tool K10. Defects such as cracks, peelings due to brittle fracture along with the direction of lamellar were observed on the machined surface. The larger brittle cracks were occurred in cutting by tool with the rake angle of +5°. For machining in the rake angle of -5°, the depth of crack occurrence was independent on the direction of lamellar. On the other hand, for machining in the rake angle of +5°, it increased rapidly at the lower angle between lamellar direction and cutting direction than 90°.

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  • 20407 Effect to the Machinability of S25C Steel with Changing Cooling Rate and Boron Content

    KUROSHIMA Yoshiharu, YAKOU Takao, SASAKI Tomohiro

    The Proceedings of Conference of Kanto Branch  2006  The Japan Society of Mechanical Engineers

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    Event date: 2006

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    Effect to the machinability of S25C steel with changing cooling rate and Boron content (S25CB) has been investigated by turning using cemented carbide tool P20. It was found that the tool wear and surface roughness for cutting S25C were lager than that for S25CB in annealed steels. However, in water(20℃) and cold water(0℃) cooled steels, the tool wear and surface roughness for cutting S25CB resulted larger than that for S25C. Moreover, chip length for cutting S25C was longer than that for S25CB in all cooling rate steels.

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  • 1604 Influence of Cutting Process of Bending Properties of Al-Si Alloy

    KAMIYA Masatsugu, NAGATSUMA Yoshiki, SASAKI Tomohiro, YAKOUI Takao

    The proceedings of the JSME annual meeting  2006  The Japan Society of Mechanical Engineers

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    Event date: 2006

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    Bending properties of Al-20%Si alloys machined by dry cutting and wet cutting are investigated in this report. Primary silicon of average size of 27μm and eutectic silicon of average size of 5μm are observed in the specimen. The bending stress was increased in order of the specimen machined by dry cutting, machined by wet cutting and polished. The machined surface by dry cutting was rough due to the detaching of the built-up edge during machining. For the machined surface by wet cutting, cracks were observed near the primary silicon particles. The decreasing of bending stress are probably due to that the splitting of the material in dry cutting is larger than the crack of primary silicon in wet cutting.

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  • 1605 Development of TiNi Actuator using Atomic Diffusion

    YAKOU Takao, SASAKI Tomohiro, YAMAMOTO Keijirou

    The proceedings of the JSME annual meeting  2006  The Japan Society of Mechanical Engineers

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    Event date: 2006

    Language:Japanese  

    Ti-Ni system alloys are processed by solid phase diffusion at 800℃ after nickel plating on titanium foils in this report. Intermetallic compound layers of Ti_2Ni, TiNi and TiNi_3 were observed in the specimens by the diffusion. TiNi layer was formed at longer diffusion time than 6h, and the thickness increased proportionally to square root of the diffusion time, t. Voids due to Kirkendall effect were observed in Nickel layer. Additionally, the number of voids increased with increasing diffusion time. However, it is clarified that the intermetallic compound layers without the voids are obtained inside of the specimen by using this method.

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  • 1606 Machinability of Ti-Al Lamellar Material at Orthogonal Cutting

    SASAKI Tomohiro, SAIKI Kaduki, YAKOU Takao, TAKAGI Shininchi

    The proceedings of the JSME annual meeting  2006  The Japan Society of Mechanical Engineers

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    Event date: 2006

    Language:Japanese  

    Machinability of Ti-47.7at% Al intermetalli compound having TiAl-Ti_3Al full lamella structure is investigated by orthogonal cutting test using cemented carbide tool K10. Defects such as cracks, peelings due to brittle fracture along with the direction of lamella were observed on the machined surface. The larger brittle cracks were occurred in cutting by tool with the rake angle of +5°. For machining in the rake angle of -5°, the depth of crack occurrence was independent on the direction of lamella. On the other hand, for machining in the rake angle of +5°, it increased rapidly at the lower angle between lamella direction and cutting direction than 90°.

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  • Machinability of Intermetallic Compound Fe3Al

    T.Sasaki, T. Yakou

    Proceedings of The Third International Conference on Leading Edge Manufacturing in 21st Century  2005.10 

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    Event date: 2005.10

    Language:English  

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  • 307 Effect of plating thickness on mechanical properties of high temperature aluminized low carbon steels

    SASAKI Tomohiro, YAOKU Takao, KOBAYASHI Shigeaki, ICHINOSE Kensuke

    2005 

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    Event date: 2005

    Language:Japanese  

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  • 2633 Machinability of Precipitation Hardened Al-4mass%Cu and Si added Al-4mass%Cu alloys

    KAMIYA Masatsugu, SASAKI Tomohiro, KAMASAKI Kengo, YAKOU Takao

    The proceedings of the JSME annual meeting  2005  The Japan Society of Mechanical Engineers

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    Event date: 2005

    Language:Japanese  

    To improve the machinability of precipitation hardened aluminum alloy, turning tests have been performed for Al-4mass%Cu and Si added Al-4mass%Cu alloys. The chip breakability improved and surface roughness increased in over aged Al-4mass%Cu alloys at dry and wet cutting conditions. On the contrary, in Si added Al-4mass%Cu alloys, chip breakability more increase at heat treated condition from solution to peak aged at wet cutting condition than dry cutting condition. Moreover, from tensile tests for these alloys at wet and dry environment, fracture elongation decrease at Si added Al-4mass%Cu alloys at wet condition. And, from SEM observation of breaked chip surface for those Si added alloys, as ovserved inter-phase fracture of Si particles by deformation, chip breaking during wet cutting of Si added Al-4mass%Cu alloys controlled by Rebinder effect of lubricant.

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  • 2631 Relationship between machinability and mechanical properties of Austenitic Stainless Steels

    KAMASAKI Kengo, UENO Yushi, SASAKI Tomohiro, YAKOU Takao

    The proceedings of the JSME annual meeting  2005  The Japan Society of Mechanical Engineers

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    Event date: 2005

    Language:Japanese  

    Relation between tool life and work hardening in cutting austenitic stainless steel is investigated by turning. The tool life is long in rank order of S35C-H, SUS304, SUSS16 and S35C-O, and tends to be short as hardness of material before machining is high. In result of observation of section through the finished surface of specimen and hardness measurement, tool cuts work hardened layer, HV=350-400, for stainless steels, especially SUS304, more work hardened layer, HV=580, is observed at 10μm depth from surface. It has been clear that the tool life was possible to be ruled by maximum hardness in work hardened layer.

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  • 2634 Machinability of intermetallic compound Fe_3Al

    SASAKI Tomohiro, YAOKU Takao

    The proceedings of the JSME annual meeting  2005  The Japan Society of Mechanical Engineers

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    Event date: 2005

    Language:Japanese  

    Intermetallic compound Fe_3Al (Fe-16mass%Al) has been processed by reactive sintering process, and the machinability has been investigated by dry turning. In cutting Fe_3Al by cemented carbide tool, the tool life were approximately one tenth of that in cutting carbon tool steel SK3 because of intense flank wear. The tool life in cutting Fe_3Al by P20 was longer than K10, and cermet tool reached to tool life by chipping at the whole cutting speed measured. The roughness of finished surface in cutting Fe_3Al by cemented carbide tool was mach smaller than SK3. However, in cutting by cermet, the roughness showed a sharp rise due to chipping. Cemented carbide P20 is suitable for cutting Fe_3Al, further, highly accurate cutting is possible in Fe_3Al because of for the good finished surface.

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  • 306 Control of Intermetallic compound layers by two-step heat treatment in aluminized steel

    Itoi Yuta, Okunuki Takashi, Sasaki Tomohiro, Kobayashi Shigeaki, Yakou Takao

    2005 

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    Event date: 2005

    Language:Japanese  

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  • 2632 Effect of boron contents of carbon steels on machinability

    KUROSHIMAI Yoshiharu, SASAKI Tomohiro, YAOKU Takao

    The proceedings of the JSME annual meeting  2005  The Japan Society of Mechanical Engineers

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    Event date: 2005

    Language:Japanese  

    Machinability of lathe machining and drill machining in structural carbon steel S25C material and S25C contained boron steels (S25CB002) have been investigated. It was clear that the tool wear of flank face in lathe machining were remarkable at boron contained steel S25CB002 than that of at S25C. Moreover, the tool wear of drill machining were larger than that of S25C.

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  • Role of Cementite on Two-Body Abrasive Wear in Steels

    SASAKI Tomohiro

    2004.3 

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    Event date: 2004.3

    Language:Japanese  

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  • Relationship between tool wear and deformed layer in turning with austenitic stainless steel

    KAMASAKI Kengo, UENO Yushi, SASAKI Tomohiro, YAKOU Takao

    The Proceedings of The Manufacturing & Machine Tool Conference  2004  The Japan Society of Mechanical Engineers

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    Event date: 2004

    Language:Japanese  

    Cause of difficultly to machine austenitic stainless steel was studied by turning with new tool or wore tool. In cutting of SUS304 with wore tool, Vichers hardness at surface reached 600 against approximately 300 at inside. We thought it was because strain induced martensitic transformation generated at surface of SUS304.

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  • Work Hardening and Machinability of Austenitic Stainless Steels

    UENO Yushi, SASAKI Tomohiro, YAKOU Takao

    The Proceedings of Conference of Kanto Branch  2004  The Japan Society of Mechanical Engineers

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    Event date: 2004

    Language:Japanese  

    The effect of stress inducted martensitic transformation on the machinabilities of austenitic stainless steels (SUS301, SUS304 and SUS316) were investigated. The yield stresses of all steels were almost the same and the work hardening were remarkable in the order of SUS301, SUS304, SUS316. The scatters and mean values of hardness distribution in tensile deformation were large in the order of SUS301, SUS304, SUS316. And tend similar to the work hardening. Moreover, these tendencies were observed in the roughness of machined surface. The machinabilities in turning of austenitic stainless steels were discussed by the relationship of the hardness and the stress inducted martensitic transformation.

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  • A Study on Machinability of Al_2O_3 Particle of Dispersion Hardened Al-Al_2O_3 Materials.

    MIURA Yusuke, YAKOU Takao, SASAKI Tomohiro

    The Proceedings of Conference of Kanto Branch  2004  The Japan Society of Mechanical Engineers

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    Event date: 2004

    Language:Japanese  

    The aluminum matrix composites reinforced with Al_2O_3 particles were processed and the effect of Al_2O_3 particles on the machinabilities of these composites were investigated. As a result, the measured Vickers hardness values rose remarkably in a critical penetrated depth of indenter. And, the critical penetrated depth increased with increasing particle volume fraction and particle size. The dependence of volume fraction and particle size on the flank wear in turning were remarkable in the depth of cut smaller than the critical depth of Vickers indenter.

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  • Relationship between Machinability and Ductility of Fe-Al Intermetallic compounds

    SASAKI Tomohiro, YAKOU Yakao

    The proceedings of the JSME annual meeting  2004  The Japan Society of Mechanical Engineers

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    Event date: 2004

    Language:Japanese  

    The machinabilities of aluminized steels were investigated by turning. The tool wear in cutting aluminized steels diffused at 1223K were more remarkably than steels as hot-dip aluminum coated, and the edge retreat amount increased with lengthening diffusion time TD. Three intermetallic compounds which were Fe_3Al, FeAl and Fe_2Al_5 formed to the diffusion layer of diffusion treated steels. In cutting frequency N was small, the machined surface roughness of diffusion treated steels were large because Fe_2Al_5 formed near the surface diffusion treated steels ware brittle fractured by impact while cutting. And, in N was large and Fe_3Al and FeAl were cut, the machined surface roughness were small. However, these intermetallic compounds caused temperature-rise and r remarkable tool wear.

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  • Analysis of deformed layer generated by machining of steel

    SASAKI Tomohiro, KAMASAKI Kengo, OHTANI Tadashi, YAKOU Takao

    The proceedings of the JSME annual meeting  2004  The Japan Society of Mechanical Engineers

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    Event date: 2004

    Language:Japanese  

    Structures of deformed layer generated by cutting of eutectoid steels and effect of cutting conditions were investigated. In cutting of eutectoid steel with spheroidal cementite structure, cementite was hardly deformed but traces caused by deformation of fearlite were observed. The area observed traces increased as rake angle in tool decreased. In cutting of eutectoid steel with pearlite structure, structures of deformed layer were differ in direction to cementite against longitudinal direction to work piece, and in case, direction to cementite was perpendicular to longitudinal direction to work piece, fracture and bend of cementite were observed, and in case, direction to cementite was parallel to it, division, slide and bend were observed. In martensite structure, thick layer was observed to outer layer and size of crystal in this layer was nano level.

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  • Machinability of glass dispersion Aluminum alloy

    KAMIYA Masatsugu, SASAKI Tomohiro, KAMASAKi Kengo, YOSGUDA Osamu, YAKOU Takao

    The proceedings of the JSME annual meeting  2004  The Japan Society of Mechanical Engineers

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    Event date: 2004

    Language:Japanese  

    As the basic research of development of composite material using aluminum can and glass both were often used as a recycling material, work pieces whish glass particles homogeneously dispersed to pure Al powder were sintered by hot press. And mechanical properties and machinability in turning of these composites were investigated. By dispersing glass particles, hardness of alloys was increased and chips were broken into small pieces. On the other hand, conditions of machined surfaces were roughening with increasing glass particle contents. Moreover cutting force was decreasing with increasing glass particle contents.

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  • Effect of Si dispersion on Machinability of Al-Cu alloys

    KAMIYA Masatsugu, KAMASAKI Kengo, SASAKI Tomohiro, YAKOU Takao

    The proceedings of the JSME annual meeting  2004  The Japan Society of Mechanical Engineers

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    Event date: 2004

    Language:Japanese  

    The effect of grain size and volume fraction of Si Particle on machinability of aluminum alloys in turning was investigated. Powders of pure Al and Al-Cu alloy were used as matrix and to disperse Si particles homogeneously, work pieces were sintered by hot press By dispersing Si particles, hardness of alloys were increased and chips were broken into small pieces. This tendency was remarkable in Si dispersion alloys based on Al-Cu. On the other hand, conditions of machined surfaces were roughen with increasing Si contents, and this tendency was slightly stronger in Al-Cu alloys than that of Al alloys.

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  • Abrasive wear and stress induced martensitic Transformation of Austenitic Steels

    Kamasaki Kengo, Sasaki Tomohiro, Yakou Takao, Ohotani Tadashi, Sakamoto Satoshi

    Proceedings of JSPE Semestrial Meeting  2004  The Japan Society for Precision Engineering

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    Event date: 2004

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  • Influence of aluminum content on machinability of intermetallic FeAl

    SASAKI Tomohiro, YAOKU Takao

    The Proceedings of The Manufacturing & Machine Tool Conference  2004  The Japan Society of Mechanical Engineers

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    Event date: 2004

    Language:Japanese  

    The machinabilities of intermetallics FeAl having various aluminum contents formed by reaction sintering were investigated by turning. Hardness of FeAl increase with increasing aluminum content. Tool wear in machining FeAl was mainly flank wear. Tool life decreased with increasing aluminum contents and this tendency was remarkable at higher than cutting velocity 1.0m/s. Machined surfaces of FeAl were smooth and clear cutting mark was found on surface at cutting velocity 0.5m/s. However, at higher than cutting velocity 1.0m/s, cutting mark was unclear and clack was found on surface of hard material having higher aluminum content. It was suggested that critical cutting velocity of FeAl using cemented Carbide P20 is about 0.5m/s.

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  • Machinability of intermetallic compound Fe_3Al

    SASAKI Tomohiro, YAOKU Takao

    The Proceedings of Ibaraki District Conference  2004  The Japan Society of Mechanical Engineers

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    Event date: 2004

    Language:Japanese  

    Machinability of Fe_3Al(Fe-16wt%Al) intermetallic compound for tungsten-carbide tool P20 was investigated by turning. Flank wear of cutting tool increases rapidly with increasing cutting velocity and the critical cutting velocity of Fe_3Al for P20 was about 0.5m/s. Difference of hardness of Fe_3Al and that of SK3 used as comparative material was small, but tool life for Fe_3Al was much shorter than that for SK3. It was suggested that the tool life shortening for Fe_3Al was caused by diffusion of tool material at high cutting velocity. As the tool wear of Fe_3Al was remarkably at higher cutting velocity, but machined surfaces of Fe_3Al were smooth than SK3.

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  • Micro-Vickers Hardness on Al_2O_3 Particle of Dispersion Hardened Al/Al_2O_3 Materials

    YAKOU Takao, MIURA Yusuke, SASAKI Tomohiro

    2003.4 

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    Event date: 2003.4

    Language:Japanese  

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  • Aluminizing of Carbon steels using Aluminum foil

    SASAKI Tomohiro, YAKOU Takao

    The Proceedings of Conference of Kanto Branch  2003  The Japan Society of Mechanical Engineers

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    Event date: 2003

    Language:Japanese  

    Two type of aluminizing test for carbon steel have been performed. The one was diffusion treated after soaking in molten aluminum bath. The other was diffusion treated after preheating where put carbon steel into aluminum foils and pressed y the ceramics plates. Later case of aluminizing test had more thin and uniform film than that of the former case. Moreover, at the diffusion treatment, more thick ductile film were formed in later case.

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  • Relationship between the Applied Force on Indenter and the Scatter of Vickers Hardness in Al-Al_2O_3 Dispersion Hardened Materials

    MIURA Yusuke, YAKOU Takao, SASAKI Tomohiro

    The Proceedings of Conference of Kanto Branch  2003  The Japan Society of Mechanical Engineers

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    Event date: 2003

    Language:Japanese  

    The hardness of Al-Al_2O_3 materials were measured at the condition of the applied force of indenter was widely changed to examine the contribution of each phase of dispersion hardened materials. The hardness scatter of Al-Al_2O_3 materials were larger as the single phase materials such as pure Al and Al_2O_3 materials, is especially at the low applied force conditions and at the Al-Al_2O_3 materials of high Al_2O_3 volume fraction. The hardness scatter came to decrease as the applied force F=5N or more it decreases to the same extent as the single phase material. The scatter of hardness under low applied force forms two or three groups, and it has been understood that the hardness of the matrix and dispersion phase appears in the lower group and the higher group, respectively.

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  • Effect of nicotine in cutting fluids on machinability of pure aluminum

    KAMIYA Masatsugu, SASAKI Tomohiro, YAKOU Takao

    2002.10 

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    Event date: 2002.10

    Language:Japanese  

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  • 408 Ductile-Brittle Transition during Abrasive Wear of Fe-Al Intermetallic Compounds

    SASAKI Tomohiro, KOBAYASHI Sigeaki, YAKOU Takao

    The Proceedings of The Manufacturing & Machine Tool Conference  2001  The Japan Society of Mechanical Engineers

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    Event date: 2001

    Language:Japanese  

    To make clear the wear property of Fe-Al intermetallic compounds, the five specimens of Fe_3Al, FeAl, FeAl_2, Fe_2Al_5 and FeAl_3 were subjected to abrasion tests using abrasive paper with some grain size. In FeAl_2, Fe_2Al_5 and FeAl_3 specimens with relatively high Al composition, the wear surface translated from ductile wear surface into brittle wear surface with chipping at the specific size of abrasive grain. The effect of applied force per abrasive grain on this ductile-brittle transition was discussed from the relationship between micro cracking condition in indentation test and grain size on abrasive paper.

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  • スペックルフリンジパターンに及ぼすアルミニウムの荷重履歴の影響

    佐々木 朋裕, 高橋 雅裕, 渡辺 健彦, 柳沢 敦

    日本機械学会 M&M2010材料力学カンファレンス  2010.10 

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    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:長岡技術科学大学  

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  • アルミニウム溶射と拡散処理によるTiAl 基合金への耐酸化コーティング

    八木崇弘, 佐々木朋裕, 渡辺健彦, 柳沢敦

    金属学会 秋季大会  2010.9 

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    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:北海道大学  

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  • アルミニウムの超音波接合における接合過程の研究

    後藤拓人, 渡辺健彦, 佐々木朋裕, 柳沢敦

    溶接学会 平成22年度秋季大会  2010.9 

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    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:日本大学 郡山キャンパス  

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  • 鉄鋼とアルミニウム合金の超音波接合

    修理翔太, 渡辺健彦, 佐々木朋裕, 柳沢敦

    溶接学会 平成22年度秋季大会  2010.9 

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    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:日本大学 郡山キャンパス  

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  • Aluminizing of TiAl-Based Alloy Using Thermal Spray Coating International conference

    T.Sasaki, T.Yagi, T.Watanabe

    The 7th Pacific Rim International Conference on Advanced Materials and Processing  2010.8 

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    Language:English   Presentation type:Poster presentation  

    Venue:Cairns, Australia  

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  • Al-Si合金の2次元切削時の被削性に及ぼすSi含有量の影響

    須貝 篤, 佐々木朋裕

    軽金属学会 第117回秋期大会  2009.11 

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    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:電気通信大学  

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Awards

  • 溶接学会論文奨励賞

    2013.4   溶接学会  

    佐々木朋裕

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    Award type:Honored in official journal of a scientific society, scientific journal  Country:Japan

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  • JWS Interfacial Joining Research Award

    2012.5  

    T.Sasaki, T.Watanabe, T.Goto, Y.Hosokawa, A.Yanagisawa

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    Award type:Award from Japanese society, conference, symposium, etc.  Country:Japan

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Research Projects

  • Development of non destructive techinique using opto-acoustic method

    Grant number:18H01722

    2018.4 - 2022.3

    System name:Grants-in-Aid for Scientific Research

    Research category:Grant-in-Aid for Scientific Research (B)

    Awarding organization:Japan Society for the Promotion of Science

    Sasaki Tomohiro

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    Grant amount:\17160000 ( Direct Cost: \13200000 、 Indirect Cost:\3960000 )

    Against the background of "Maltimatrialization", development of a non-destructive techinique for disimiller bonded materials including metals, plastics are performed. The analysis focuses on residual stress in the vicinity of the bonded interface. An optical interferrometer is deviced to visuliaze the deforamtion behavior of material in two dimension and full field. The device is capable of visuallizing dynamic deformation when the materials are subjected to a minimul and reversible deformation. This project demonstrates the feasibility of a new technique of reisdual stress estimation.

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  • 超音波接合における相対運動の制御と最適化

    2014.4

    System name:科学研究費助成事業

    Research category:基盤研究(C)

    Awarding organization:日本学術振興会

    佐々木朋裕

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    Authorship:Principal investigator  Grant type:Competitive

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  • Relative motion control and optimization of ultrasonic bonding

    Grant number:26420696

    2014.4 - 2017.3

    System name:Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)

    Research category:Grant-in-Aid for Scientific Research (C)

    Awarding organization:Japan Society for the Promotion of Science

    Sasaki Tomohiro

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    Grant amount:\5200000 ( Direct Cost: \4000000 、 Indirect Cost:\1200000 )

    This study deals with one of solid state bonding techniques, “ultrasonic bonding” which utilizes high frequency vibration to bond metals. The bonding phenomena is analyzed by a combination approach of microstructural evaluation of bonding interface and dynamic motion analysis using in-situ observation. The study revealed that the correlation of a relative motion involving the bonding metals and bonding tools to apply the vibration, as well as the microstructural evolution at the bonding interface. A new ultrasonic bonding technique capable of high speed and high reliability bonding has been discussed.

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  • Analysis of Ultrasonic Welding Process using Optical Measurement

    Grant number:23760689

    2011 - 2013

    System name:Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)

    Research category:Grant-in-Aid for Young Scientists (B)

    Awarding organization:Japan Society for the Promotion of Science

    SASAKI Tomohiro

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    Grant amount:\2210000 ( Direct Cost: \1700000 、 Indirect Cost:\510000 )

    Basic study on ultrasonic welding, which is one of solid state bonding technique, has been performed using motion analysis by optical measurement. Relative motion of weld tool, with respect to the working materials, during ultrasonic welding tests are analyzed using the digital correlation method. The dynamic behavior of material during the ultrasonic welding has been evaluate applying the result of motion analysis to the visualization of strain field. It has been clarified that the relative motion between the weld tool and work material strongly affect the microstructure development at the weld interface.

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  • マルチマテリアル化に対応した異材接合部の非破壊検査

    Grant number:23H01724

    2023.4 - 2026.3

    System name:科学研究費助成事業

    Research category:基盤研究(B)

    Awarding organization:日本学術振興会

    佐々木 朋裕

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    Grant amount:\18330000 ( Direct Cost: \14100000 、 Indirect Cost:\4230000 )

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  • Development of an education program for promoting higher-level engineers by considering their diverse study history

    Grant number:26301042

    2014.4 - 2019.3

    System name:Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

    Research category:Grant-in-Aid for Scientific Research (B)

    Awarding organization:Japan Society for the Promotion of Science

    Sato Takashi

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    Grant amount:\13520000 ( Direct Cost: \10400000 、 Indirect Cost:\3120000 )

    The development of an education program promoting higher-level engineers, that takes their diverse study histories into consideration is our main goal. Education systems in Japan, such as Technical High Schools, Technical Colleges, Technical Junior Colleges, Universities, and Graduate Schools. While it is true that the numbers of both female-, as well as foreign- students in Engineering fields are increasing, they are not yet at desired levels. Diversity in Engineering Education is necessary both in Japan and in the view point of Japanese contribution to international society, which is now globalized in many fields. The globalization of the Japanese Engineering Education System is vitally important for exporting both industrial products and Japanese Engineering Education systems.
    We are extremely proud of our success, having grown students who have both the ability to explore the subject and make meaningful contributions in globalized society in our program.

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  • ステンレス鋼のレーザー溶接に関する研究

    2012.4 - 2014.3

    System name:共同研究(国内共同研究)

    Awarding organization:ダイニチ工業株式会社

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    Grant type:Competitive

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  • アルミニウム合金の超音波接合に関する研究

    2012.4 - 2014.3

    System name:平成24年度アルミニウム研究助成

    Awarding organization:民間財団等

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    Grant type:Competitive

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  • 異種ステンレス鋼板の溶接の研究

    2010.4 - 2012.3

    System name:共同研究(国内共同研究)

    Awarding organization:吉田金属工業株式会社

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    Grant type:Competitive

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  • 電子スペックル干渉法を用いた金属材料の寿命評価

    2009.4 - 2010.3

    System name:内田エネルギー科学振興財団 試験研究費

    Awarding organization:民間財団等

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    Grant type:Competitive

    近年、省エネルギー、省資源化の観点から構造材料の高寿命化が望まれ、維持管理のための非破壊検査、材料寿命予測はさらに重要性を増している。これまで材料の寿命予測は亀裂進展特性の解析によって行われるため、工業的な非破壊検査は超音波探傷やアコースティックエミッション等を用いた亀裂の検出が主目的とされてきた。しかし、材料の高機能化、ナノ・マイクロ化に伴い従来の経験的パラメータに依存した対応が難しくなってきている。そこで本研究ではレーザー光学的手法を用いた新しい材料寿命評価および解析技術開発のための基礎研究を行う。具体的にはアルミニウムおよび鋼といった汎用金属を対象として、レーザー干渉計を用いた全視野計測により材料の塑性変形、破断時の応力集中および亀裂の存在よって生ずる不均一変形挙動の調査を行う。不均一変形に伴うレーザー干渉模様の変化を評価することで、金属材料の変形・破壊現象の根本的な理解をするととも

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  • Improvement of high temperature property of TiAl based alloy using Al diffusion to machining defect

    Grant number:21760579

    2009 - 2010

    System name:Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)

    Research category:Grant-in-Aid for Young Scientists (B)

    Awarding organization:Japan Society for the Promotion of Science

    SASAKI Tomohiro

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    Grant amount:\1690000 ( Direct Cost: \1300000 、 Indirect Cost:\390000 )

    To improve mechanical property and oxidation resistance of machined TiAl based alloys, Al diffusion treatment using Two-step process of an aluminum coating and a diffusion treatment was performed. The formation process of intermetallic layer during the diffusion treatment was investigated, and an optimum condition to resolve the machined defects was evaluated. In addition, the coating stability in high temperature oxidation was invesitigated.

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  • アルミニウム合金と工具との凝着性に関する研究

    2007.10 - 2009.10

    System name:アルミニウム研究助成

    Awarding organization:民間財団等

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    Grant type:Competitive

    Grant amount:\800000 ( Direct Cost: \800000 )

    切削加工や塑性加工において,Al合金とそれを変形加工する工具とは温度と圧力とが高い条件下におかれる.このような場合に被加工物であるAl合金が工具表面に移着したり,工具構成材料がAl合金中に拡散したりする現象が頻繁に生ずる.特に無潤滑化では著しい.この中で,被加工物が工具表面へ移着する現象は「凝着」の問題として扱われ,凝着核の発生と成長の問題として鋼と高速度工具鋼に対して一例ある以外は,凝着が発生する事例研究は多く見られるものの,核発生,成長の立場から科学的に扱った報告は見られない.そこで本研究では,工具とAl合金の高温・高圧力下で生ずる凝着の核の発生とその成長機構を解明することを目的とする.

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Teaching Experience (researchmap)

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Teaching Experience

  • 総合技術科学演習

    2023
    Institution name:新潟大学

  • マーケット・インターンシップ

    2023
    Institution name:新潟大学

  • 創造研究プロジェクトI

    2023
    Institution name:新潟大学

  • テクノロジー・インターンシップ

    2023
    Institution name:新潟大学

  • 創造プロジェクトII

    2023
    Institution name:新潟大学

  • 創造プロジェクトI

    2023
    Institution name:新潟大学

  • 創造プロジェクト基礎

    2023
    Institution name:新潟大学

  • 創造研究プロジェクトII

    2023
    Institution name:新潟大学

  • 材料力学II

    2021
    Institution name:新潟大学

  • 材料力学I

    2021
    Institution name:新潟大学

  • 材料力学入門

    2021
    Institution name:新潟大学

  • 異文化と技術

    2021
    Institution name:新潟大学

  • 接合加工学特論

    2021
    Institution name:新潟大学

  • 自然科学総論II

    2021
    Institution name:新潟大学

  • 機械工学実験III

    2020
    Institution name:新潟大学

  • 卒業研究

    2020
    Institution name:新潟大学

  • 先端研究入門

    2020
    Institution name:新潟大学

  • 機械工学実験IV

    2020
    Institution name:新潟大学

  • 英文輪読II

    2020
    Institution name:新潟大学

  • 機械材料

    2019
    Institution name:新潟大学

  • 卒業研修

    2019
    Institution name:新潟大学

  • 英文輪読I

    2019
    Institution name:新潟大学

  • 工学リテラシー入門(力学分野)

    2018
    Institution name:新潟大学

  • 機械工作実習I

    2018
    -
    2021
    Institution name:新潟大学

  • 工業力学

    2018
    -
    2021
    Institution name:新潟大学

  • 機械工作実習II

    2018
    -
    2021
    Institution name:新潟大学

  • 機械工作実習III

    2018
    -
    2021
    Institution name:新潟大学

  • 物理工学実験

    2017
    Institution name:新潟大学

  • 機械工学概論

    2017
    Institution name:新潟大学

  • 機械工学実験II

    2016
    Institution name:新潟大学

  • 機械工学演習

    2016
    Institution name:新潟大学

  • 機械工学実験I

    2016
    Institution name:新潟大学

  • 異文化と技術

    2016
    -
    2018
    Institution name:新潟大学

  • 機械材料学特論

    2013
    Institution name:新潟大学

  • 接合加工学特論

    2013
    -
    2019
    Institution name:新潟大学

  • 材料創造工学

    2013
    -
    2018
    Institution name:新潟大学

  • 工学リテラシー入門(機械システム工学科)

    2013
    -
    2016
    Institution name:新潟大学

  • 材料生産システム特定研究Ⅱ

    2013
    -
    2015
    Institution name:新潟大学

  • 研究発表演習・発表

    2013
    -
    2015
    Institution name:新潟大学

  • 材料生産システム特定研究Ⅰ

    2013
    -
    2015
    Institution name:新潟大学

  • 機械科学セミナーⅡ

    2013
    -
    2015
    Institution name:新潟大学

  • 機械科学セミナーⅠ

    2013
    -
    2015
    Institution name:新潟大学

  • 構造用材料学

    2012
    -
    2020
    Institution name:新潟大学

  • 機械科学特別演習

    2012
    -
    2015
    Institution name:新潟大学

  • 機械科学文献詳読Ⅰ

    2012
    -
    2015
    Institution name:新潟大学

  • 機械科学文献詳読Ⅱ

    2012
    -
    2015
    Institution name:新潟大学

  • 材料組織学

    2011
    -
    2020
    Institution name:新潟大学

  • くらしを支える機械システム工学

    2010
    Institution name:新潟大学

  • 機械機能性材料学

    2009
    -
    2020
    Institution name:新潟大学

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