2021/04/20 更新

写真a

ササキ トモヒロ
佐々木 朋裕
SASAKI Tomohiro
所属
教育研究院 自然科学系 生産デザイン工学系列 教授
工学部 工学科 教授
職名
教授
外部リンク

学位

  • 博士(工学) ( 2006年3月   横浜国立大学 )

研究分野

  • ものづくり技術(機械・電気電子・化学工学) / 計測工学  / 光応用計測

  • ナノテク・材料 / 材料加工、組織制御

  • ものづくり技術(機械・電気電子・化学工学) / 材料力学、機械材料  / 材料接合

経歴(researchmap)

  • 新潟大学   大学院自然科学研究科   教授

    2020年4月 - 現在

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    国名:日本国

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  • 新潟大学   自然科学研究科 材料生産システム専攻 機械科学   准教授

    2012年10月 - 現在

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  • 新潟大学   大学院自然科学研究科   准教授

    2012年10月 - 2020年3月

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  • 新潟大学   工学部 機械システム工学科 機能開発工学   助教

    2009年4月 - 2012年9月

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  • サウスイースタン ルイジアナ大学   客員研究員

    2008年7月 - 2009年3月

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  • 横浜国立大学   特別研究教員

    2007年4月 - 2009年3月

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  • 横浜国立大学   助手

    2006年4月 - 2007年4月

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▶ 全件表示

経歴

  • 新潟大学   工学部 工学科   教授

    2020年4月 - 現在

  • 新潟大学   自然科学研究科 材料生産システム専攻 機械科学   准教授

    2012年10月 - 2020年3月

  • 新潟大学   機械システム工学科   准教授

    2012年10月 - 2020年3月

  • 新潟大学   機能開発工学   助教

    2009年4月 - 2012年9月

学歴

  • 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年4月 - 2006年3月

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    国名: 日本国

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  • 横浜国立大学   Graduate School, Division of Engineering  

    - 2003年3月

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    国名: 日本国

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  • 横浜国立大学   Faculty of Engineering   Department of Mechanical Engineering and Materials

    - 2001年3月

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    国名: 日本国

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所属学協会

 

論文

  • Dynamic ESPI Evaluation of Deformation and Fracture Mechanism of 7075 Aluminum Alloy 査読

    Shun Takahashi, Sanichiro Yoshida, Tomohiro Sasaki, Tyler Hughes

    Materials14 ( 6 ) 1530 - 1530   2021年3月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元: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 査読

    Sanichiro Yoshida, Conor McGibboney, Tomohiro Sasaki

    APPLIED SCIENCES-BASEL10 ( 16 )   2020年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:MDPI  

    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 査読

    Sanichiro Yoshida, Tomohiro Sasaki

    MATERIALS13 ( 6 )   2020年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:MDPI  

    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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  • 有限要素法を用いた丸棒鋼ガス圧接部の加熱変形解析 査読

    伊藤 太初, 山本 隆一, 佐々木 朋裕

    溶接学会論文集38 ( 4 ) 418 - 428   2020年

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    記述言語:日本語   出版者・発行元:一般社団法人 溶接学会  

    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 査読

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

    MATERIALS12 ( 24 )   2019年12月

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    担当区分:筆頭著者, 責任著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元: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 査読

    Keisuke Arimoto, Tomohiro Sasaki, Yuhei Doi, Taewon Kim

    METALS9 ( 5 )   2019年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:MDPI  

    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 査読

    Takumi Kamimura, Sanichiro Yoshida, Tomohiro Sasaki

    APPLIED SCIENCES-BASEL8 ( 7 )   2018年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:MDPI  

    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 査読

    Tomohiro Sasaki, Tatsushi Nagai, Takehiko Watanabe

    Welding International32 ( 2 ) 95 - 102   2018年2月

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    掲載種別:研究論文(学術雑誌)  

    © 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 査読

    Tomohiro Sasaki, Kazuki Komiyama, Jonas A. Pramudita

    JOURNAL OF MATERIALS PROCESSING TECHNOLOGY252   167 - 175   2018年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    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 査読

    T. Sasaki, T. Yagi

    Surface Engineering32 ( 11 ) 809 - 815   2016年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Taylor and Francis Ltd.  

    © 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 査読

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

    APPLIED SCIENCES-BASEL6 ( 6 )   2016年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:MDPI AG  

    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 査読

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

    ULTRASONICS67   9 - 17   2016年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    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 査読

    Kazuki Komiyama, Tomohiro Sasaki, Yusuke Watanabe

    JOURNAL OF MATERIALS PROCESSING TECHNOLOGY229   714 - 721   2016年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元: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 査読

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

    MATERIALS9 ( 2 )   2016年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:MDPI  

    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 Mesomechanics19 ( 1 ) 41 - 54   2016年1月

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    掲載種別:研究論文(学術雑誌)  

    © 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 査読

    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   129 - 137   2016年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:SPRINGER  

    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.

    DOI: 10.1007/978-3-319-21765-9_17

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

    T. Sasaki, T. Yagi

    SURFACE ENGINEERING32 ( 11 ) 809 - 815   2016年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:TAYLOR & FRANCIS LTD  

    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.

    DOI: 10.1179/1743294415Y.0000000032

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  • 軟鋼と5052アルミニウム合金の超音波接合過程の解析 招待 査読

    佐々木 朋裕, 永井 達士, 渡辺 健彦

    軽金属溶接53 ( 11 ) 448 - 454   2015年

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    記述言語:日本語   出版者・発行元:一般社団法人 軽金属溶接協会  

    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.

    DOI: 10.11283/jlwa.53.448

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  • Ultrasonic brazing of magnesium alloy

    Takehiko Watanabe, Hideki Saito, Atsushi Yanagisawa, Tomohiro Sasaki

    Welding International28 ( 3 ) 184 - 189   2014年3月

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    掲載種別:研究論文(学術雑誌)  

    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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  • Ultrasonic spot welding of galvanized steel sheet

    Naho Kaneko, Tomohiro Sasaki

    Advanced Materials Research922   332 - 337   2014年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:Trans Tech Publications  

    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.

    DOI: 10.4028/www.scientific.net/AMR.922.332

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  • Effect of tool geometry on ultrasonic welding process 査読

    Tomohiro Sasaki, Yutaro Sakata, Takehiko Watanabe

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

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IOP PUBLISHING LTD  

    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.

    DOI: 10.1088/1757-899X/61/1/012006

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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 Research922   322 - 327   2014年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:Trans Tech Publications  

    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.

    DOI: 10.4028/www.scientific.net/AMR.922.322

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

    S. Yaoita, T. Watanabe, T. Sasaki

    Materials Research Innovations17 ( SUPPL 2 ) S142 - S147   2013年12月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    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 査読

    T. Sasaki, S. Yoshida

    PHYSICAL MESOMECHANICS15 ( 1-2 ) 47 - 57   2012年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:SPRINGER  

    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.

    DOI: 10.1134/S1029959912010055

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

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

    Science and Technology of Welding and Joining18 ( 1 ) 19 - 24   2012年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    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.

    DOI: 10.1179/1362171812Y.0000000066

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

    Yaoita Shinji, Watanabe Takehiko, Sasaki Tomohiro

    Yosetsu Gakkai Ronbunshu/Quarterly Journal of the Japan Welding Society30 ( 4 ) 298 - 305   2012年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    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.

    DOI: 10.2207/qjjws.30.298

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  • デジタル画像相関法によるアルミニウムの超音波接合過程の解析 査読

    佐々木 朋裕, 渡辺 健彦, 後藤 拓人, 細川 祐介, 柳沢 敦

    溶接学会論文集30 ( 2 ) 125 - 132   2012年

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    記述言語:日本語   出版者・発行元:一般社団法人 溶接学会  

    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.

    DOI: 10.2207/qjjws.30.125

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  • 超硬合金の銀ろう付におけるろう材中のNiとCoの効果 査読

    矢尾板 信二, 渡辺 健彦, 佐々木 朋裕

    溶接学会論文集30 ( 4 ) 298 - 305   2012年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:一般社団法人 溶接学会  

    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.

    DOI: 10.2207/qjjws.30.298

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

    Takahiro Yagi, Tomohiro Sasaki, Takehiko Watanabe, Atsushi Yanagisawa

    Advanced Materials Research409   820 - 825   2012年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    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.

    DOI: 10.4028/www.scientific.net/AMR.409.820

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  • Brazing of cemented carbides at lower temperatures

    Shinji Yaoita, Takehiko Watanabe, Tomohiro Sasaki

    Advanced Materials Research409   865 - 870   2012年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    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.

    DOI: 10.4028/www.scientific.net/AMR.409.865

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

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

    Science and Technology of Welding and Joining18 ( 1 ) 19 - 24   2012年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    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.

    DOI: 10.1179/1362171812Y.0000000066

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  • 低融点銀ろうによる超硬合金のろう付 査読

    矢尾板 信二, 渡辺 健彦, 佐々木 朋裕

    溶接学会論文集 : quarterly journal of the Japan Welding Society29 ( 3 ) 204 - 209   2011年12月

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    記述言語:日本語   出版者・発行元:一般社団法人 溶接学会  

    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.

    DOI: 10.2207/qjjws.29.204

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

    T. Watanabe, A. Yanagisawa, T. Sasaki

    SCIENCE AND TECHNOLOGY OF WELDING AND JOINING16 ( 6 ) 502 - 508   2011年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:MANEY PUBLISHING  

    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.

    DOI: 10.1179/1362171811Y.0000000037

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

    Tomohiro Sasaki, Takahiro Yagi, Takehiko Watanabe, Atsushi Yanagisawa

    SURFACE & COATINGS TECHNOLOGY205 ( 13-14 ) 3900 - 3904   2011年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    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.

    DOI: 10.1016/j.surfcoat.2011.02.025

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  • 低シリコン含有ニッケル基ろうの開発研究

    渡辺 健彦, 若月 健, 柳沢 敦, 佐々木 朋裕

    溶接学会論文集29 ( 4 ) 241 - 247   2011年

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    記述言語:日本語   出版者・発行元:一般社団法人 溶接学会  

    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.

    DOI: 10.2207/qjjws.29.241

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  • 回転プローブによる工業用純チタンとアルミニウム合金の固相接合 査読

    渡辺 健彦, 吉田 亮, 柳沢 敦, 佐々木 朋裕

    溶接学会論文集 : quarterly journal of the Japan Welding Society28 ( 2 ) 255 - 260   2010年12月

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    記述言語:日本語   出版者・発行元:一般社団法人 溶接学会  

    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.

    DOI: 10.2207/qjjws.28.255

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  • マグネシウム合金の超音波ろう付 査読

    渡辺 健彦, 齋藤 秀輝, 柳沢 敦, 佐々木 朋裕

    溶接学会論文集 : quarterly journal of the Japan Welding Society28 ( 1 ) 80 - 85   2010年12月

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    記述言語:日本語   出版者・発行元:一般社団法人 溶接学会  

    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 査読

    Takehiko Watanabe, Masataka Shiroki, Atsushi Yanagisawa, Tomohiro Sasaki

    JOURNAL OF MATERIALS PROCESSING TECHNOLOGY210 ( 12 ) 1646 - 1651   2010年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    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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  • 低融点銀ろうの開発研究 査読

    渡辺 健彦, 黄 仁惠, 柳沢 敦, 佐々木 朋裕

    溶接学会論文集28 ( 4 ) 402 - 407   2010年

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    記述言語:日本語   出版者・発行元:一般社団法人 溶接学会  

    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.

    DOI: 10.2207/qjjws.28.402

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  • 炭素窒素無添加Fe‐12Ni‐9Co‐10W系オーステナイト合金のアルミナイズ処理によるFeAl皮膜生成と水蒸気中酸化挙動 査読

    有川 秀一, 宗木 政一, 大久保 弘, 阿部 冨士雄, 佐々木 朋裕, 八高 隆雄

    日本金属学会誌73 ( 4 ) 255 - 261   2009年

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    記述言語:日本語   出版者・発行元:公益社団法人 日本金属学会  

    &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>

    DOI: 10.2320/jinstmet.73.255

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  • 金型用鋼SKD61の高温アルミナイジング処理によって形成される合金層組織 査読

    尾堂 太亮, 佐々木 朋裕, 八高 隆雄, 楳田 晃裕, 登丸 雅英

    鉄と鋼95 ( 6 ) 483 - 488   2009年

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    記述言語:日本語   出版者・発行元:一般社団法人 日本鉄鋼協会  

    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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  • 軟鋼とマグネシウム合金の抵抗スポット溶接 査読

    渡辺 健彦, 鈴木 悠史, 柳沢 敦, 佐々木 朋裕

    溶接学会論文集27 ( 3 ) 202 - 207   2009年

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    記述言語:日本語   出版者・発行元:一般社団法人 溶接学会  

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

    Masatsugu Kamiya, Takao Yakou, Tomohiro Sasaki, Yoshiki Nagatsuma

    MATERIALS TRANSACTIONS49 ( 3 ) 587 - 592   2008年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:JAPAN INST METALS  

    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.

    DOI: 10.2320/matertrans.L-MRA2007886

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

    Tomohiro Sasaki, Takao Yakou

    JOURNAL OF MATERIALS PROCESSING TECHNOLOGY197 ( 1-3 ) 89 - 95   2008年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    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 査読

    Tomohiro Sasaki, Takao Yakou

    ISIJ INTERNATIONAL47 ( 7 ) 1016 - 1022   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IRON STEEL INST JAPAN KEIDANREN KAIKAN  

    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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  • Al‐Si二元合金鋳造材の旋削被削性に及ぼすSi含有量の影響 査読

    神谷 昌嗣, 八高 隆雄, 佐々木 朋裕, 長妻 慶樹

    軽金属57 ( 5 ) 191 - 196   2007年

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    記述言語:日本語   出版者・発行元:一般社団法人 軽金属学会  

    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 査読

    Tomohiro Sasaki, Takao Yakou

    JSME International Journal, Series C: Mechanical Systems, Machine Elements and Manufacturing49 ( 2 ) 334 - 339   2006年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    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 査読

    Tomohiro Sasaki, Takao Yakou

    SURFACE & COATINGS TECHNOLOGY201 ( 6 ) 2131 - 2139   2006年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    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.

    DOI: 10.1016/j.surfcoat.2006.03.018

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  • Two-body abrasive wear property of cementite 査読

    T Sasaki, T Yakou, M Umemoto, Y Todaka

    WEAR260 ( 9-10 ) 1090 - 1095   2006年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    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.

    DOI: 10.1016/j.wear.2005.07.010

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

    T Sasaki, T Yakou, K Mochiduki, K Ichinose

    ISIJ INTERNATIONAL45 ( 12 ) 1887 - 1892   2005年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IRON STEEL INST JAPAN KEIDANREN KAIKAN  

    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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  • アルミニウム箔を利用した軟鋼のアルミナイズ処理 査読

    佐々木 朋裕, 八高 隆雄

    鐵と鋼 : 日本鐡鋼協會々誌89 ( 12 ) 1227 - 1232   2003年12月

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    記述言語:日本語   出版者・発行元:社団法人日本鉄鋼協会  

    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.

    DOI: 10.2355/tetsutohagane1955.89.12_1227

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  • Fe-Al系金属間化合物の2元アブレシブ摩耗 査読

    八高 隆雄, 佐々木 朋裕, 小林 重昭

    鐵と鋼 : 日本鐡鋼協會々誌89 ( 11 ) 1178 - 1182   2003年11月

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    記述言語:日本語   出版者・発行元:社団法人日本鉄鋼協会  

    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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▶ 全件表示

MISC

受賞

  • 溶接学会論文奨励賞

    2013年4月   溶接学会  

    佐々木朋裕

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    受賞区分:学会誌・学術雑誌による顕彰  受賞国:日本国

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  • 界面接合研究賞

    2012年5月   一般社団法人 溶接学会  

    佐々木朋裕, 渡辺 健彦, 後藤 拓人, 細川 祐介, 柳沢 敦

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    受賞区分:国内学会・会議・シンポジウム等の賞  受賞国:日本国

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共同研究・競争的資金等の研究

  • 光音響学的手法による異材接合部の非破壊評価技術の開発

    研究課題/領域番号:18H01722  2018年04月 - 2022年03月

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    佐々木 朋裕, 坂本 秀一, プラムディタ ジョナス

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    配分額:17160000円 ( 直接経費:13200000円 、 間接経費:3960000円 )

    2019年度は,前年度に開発した2波長のレーザー光源ESPI装置を用いた基礎実験として,熱変形の可視化実験を行った.また,本ESPI装置には,材料変形を可視化しながら,局所加熱を行うための赤外レーザーを新たに追加した.残留応力を模擬して,材料に対して引張試験機による外部変位,あるいは静荷重を与えた状態で,材料の一部を赤外レーザーにより加熱し,その熱変形挙動をESPI装置により可視化した.ESPIにおいて必要となる干渉縞模様から変位分布を算出する過程においては,熱変形における干渉縞の位相変化を動的に解析するプログラムを新たに作成した.材料の弾性率,および熱膨張係数の応力依存性に起因して,外部応力下における材料の熱変形挙動が変化することを確認した.また,その変化は,±10℃程度の微小熱変形においても十分に検出できることを明らかにした.この結果は,残留応力が接合体の接合部近傍の局所熱膨張挙動を可視化することで,残留応力を推定できる可能性を示している.異種材接合体の例として,鋼と超硬合金をろう付接合部周辺の熱変形挙動を同様の手法で測定した.熱変形挙動と上述の基礎実験結果との比較から推定される残留応力は,定性的ではX線回折法による残留応力の測定結果に類似した分布を示した.一方,材料に微小変形を与える手法として,低周波振動から超音波における接合部近傍の音響伝搬特性を調べた.接合プロセス因子と熱変形挙動,ならびに音響波によって生じる微小変形の関係を評価するとともに,有限要素解析による変形モデルを構築した.

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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年04月 - 現在

    日本学術振興会  科学研究費助成事業  基盤研究(C)

    佐々木朋裕

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    担当区分:研究代表者  資金種別:競争的資金

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  • 超音波接合における相対運動の制御と最適化

    研究課題/領域番号:26420696  2014年04月 - 2017年03月

    日本学術振興会  科学研究費助成事業 基盤研究(C)  基盤研究(C)

    佐々木 朋裕

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    配分額:5200000円 ( 直接経費:4000000円 、 間接経費:1200000円 )

    本研究は,金属材料を加圧し,超音波振動を付加することで接合を行う超音波接合法を対象としている.本接合法では,超音波振動により接合界面を摩擦させることにより,界面密着や酸化被膜の破壊,排出を経て接合が達成される.本研究では,これらを引き起こすための接合材同士,ならびに接合工具と被接合材に生じる相対運動挙動の詳細な理解を図るとともにその制御の可能性を検討した.これにより,接合される材料,および振動を付加する接合工具との間に生じる相対運動と接合界面の組織形成との相関を明らかした.以上の実験により得られた知見を活用し,高信頼化,高性能化を実現した新しい超音波接合技術の可能性を検討した.

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  • 光学的計測法を用いた超音波接合メカニズムの解明

    研究課題/領域番号:23760689  2011年 - 2013年

    日本学術振興会  科学研究費助成事業 若手研究(B)  若手研究(B)

    佐々木 朋裕

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    配分額:2210000円 ( 直接経費:1700000円 、 間接経費:510000円 )

    金属材料の固相接合法の一種である超音波接合を対象として,接合界面組織の金属学的評価に加えて,デジタル画像相関法による接合中の材料および接合工具の相対運動解析を行った.さらに,接合界面近傍の塑性変形領域におけるひずみ場の可視化を試みることにより,超音波接合プロセスにおける接合材の動的挙動を定量的に評価した.相対運動挙動の観点から超音波接合過程を考察し,振動を付加する工具と接合する材料の相対運動が接合組織に及ぼす影響を明らかにした.

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  • 多様な学習歴を活かした工学系高度専門職業人養成カリキュラムの開発

    研究課題/領域番号:26301042  2014年04月 - 2019年03月

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    佐藤 孝, 清水 忠明, 坂本 秀一, 後藤 康志, 佐々木 朋裕, 岡 徹雄, 田邊 裕治, 平尾 篤利

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    配分額:13520000円 ( 直接経費:10400000円 、 間接経費:3120000円 )

    課題探求能力と国際的競争力を持った人材の育成を目指す工学教育の検討を行った結果,工学教育におけるダイバーシティの重要性が明らかになった。日本には,工業高校から工学系大学院まで,教育システムとしては様々なレベルの工学教育がある。また,留学生や工学系の女子学生は増えつつあるが,まだ工学教育の中心にはなっていない。
    工学教育におけるダイバーシティは,日本国内において必要であると同時に,グローバル化された国際社会への日本の貢献の観点からも必要である。今後は,工学製品だけでなく,工学教育システムの輸出も含めて,日本の工学教育システムのグローバル化が重要である。

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  • ステンレス鋼のレーザー溶接に関する研究

    2012年04月 - 2014年03月

    ダイニチ工業株式会社  共同研究(国内共同研究) 

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    資金種別:競争的資金

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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年04月 - 2014年03月

    民間財団等  平成24年度アルミニウム研究助成 

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    資金種別:競争的資金

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  • 異種ステンレス鋼板の溶接の研究

    2010年04月 - 2012年03月

    吉田金属工業株式会社  共同研究(国内共同研究) 

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    資金種別:競争的資金

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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年04月 - 2010年03月

    民間財団等  内田エネルギー科学振興財団 試験研究費 

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    資金種別:競争的資金

    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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  • TiAl基合金損傷部へのAl拡散による高温特性の改善

    研究課題/領域番号:21760579  2009年 - 2010年

    日本学術振興会  科学研究費助成事業 若手研究(B)  若手研究(B)

    佐々木 朋裕

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    配分額:1690000円 ( 直接経費:1300000円 、 間接経費:390000円 )

    TiAl基合金の耐酸化性および機械加工後の機械的強度を改善することを目的として、切削加工したTiAl基合金に対して,Alコーティングと拡散処理を組み合わせたAl拡散処理を行った。拡散処理中の金属間化合物層の生成過程を調べ,加工欠陥解消のための最適条件を検討した.さらに,Al拡散コーティングの高温酸化雰囲気中での耐酸化性を明らかにし,本処理がTiAl基合金の高温特性を改善に有効であることを示した.

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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年10月 - 2009年10月

    民間財団等  アルミニウム研究助成 

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    資金種別:競争的資金

    配分額:800000円 ( 直接経費:800000円 )

    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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