研究者詳細 - 上森　武

論文 - 上森　武

分割表示 118 件中 21 - 40 件目／全件表示 >>

引張および疲労負荷を受ける純チタン細線の破壊予測に向けた直流電位差および直径分布の変化の分析査読

坂本惇司, 高木佑輔, 上森武, 多田直哉

日本機械学会論文集 86 ( 882 ) 19 - 00351 2020年2月

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：一般社団法人日本機械学会

<p>Pure titanium thin wires have been used for medical fields. It is important to investigate the possibility of non-destructive inspection of pure titanium thin wires for the safety utilization of them. In order to investigate a fracture prediction method for a pure titanium thin wire, we performed tensile and fatigue tests and a finite element analysis to analyze the changes of direct current potential difference and diameter distribution of the pure titanium thin wire during tensile and fatigue tests. It was found that a direct current potential difference method may be available for evaluating the tensile and fatigue damages of the pure titanium thin wire. In the tensile and fatigue tests, the normalized direct current potential difference increased almost linearly with an increase in the nominal strain, and a sign of an increase of the normalized direct current potential difference was observed when the fatigue crack propagated. Therefore, the nondestructive inspection could be conducted by setting a tolerance value of the normalized direct current potential difference, or detecting a sign of an increase in the normalized direct current potential difference. In addition, a method of predicting the fracture location from the diameter distribution change of the pure titanium thin wire was studied. The method could be applied to tensile and fatigue fractures.</p>

DOI： 10.1299/transjsme.19-00351

CiNii Article

researchmap

Microscopic deformation of thin sheet of polycrystalline pure titanium under tension 査読

Naoya Tada, Kentaro Kishimoto, Takeshi Uemori, Junji Sakamoto

American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP 3 2020年

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）

Copyright © 2020 ASME. Commercial pure titanium has been widely used in aerospace, chemical, and biomedical industries for its lightweight, high corrosion resistance, high strength, high heat resistance and good biocompatible properties. The market of pure titanium thin sheets is expected to increase in medical, dental, civil engineering, and acoustical engineering fields. On the other hand, pure titanium takes hexagonal closed-pack structure with anisotropic elasticity and plasticity. Inhomogeneous microscopic deformation always occurs by mechanical loading from the elastic condition. The inhomogeneity brings about various damages such as localized plastic deformation, microcracking, necking, and so on. Since the inhomogeneity is significant in thin sheets, it is important to investigate its deformation behavior. In this study, a tensile test was carried out using a thin sheet specimen of polycrystalline pure titanium, and the microscopic deformation of grains was measured by the digital holographic microscope. During the test, the height distribution of grains was measured in a fixed area on the front and back surfaces of the specimen at each tensile load step and the results at different load steps were compared. It was found from the measurement results that inhomogeneous deformation began at the small load due to anisotropic elasticity of crystal grains and expanded with the load by their anisotropic plasticity. Grain heights at grain center and those along grain boundaries were related with each other, and the grain heights on the front surface were inversely correlated with those on the back surface.

DOI： 10.1115/PVP2020-21715

Scopus

researchmap

Slip Deformation of Crystal Grains in Semi-Circular Notched Thin Sheet Specimen of Pure Titanium during Tensile Test 査読

Takashi Ishida, Naoya Tada, Takeshi Uemori, Junji Sakamoto

Proceedings of the International Conference on Advanced Technology in Experimental Mechanics 2019 (ATEM ‘19) 2019年10月

Prediction of Fracture Location in Tensile Test of Short-Fiber-Self-Reinforced Polyethylene Composite Plates 査読

Naoya Tada, Ming Jin, Takeshi Uemori, Junji Sakamoto

Conference Papers, ASME 2019 Pressure Vessels and Piping Conference (PVP2019) 3 2019年7月

Effect of Lubrication and Forging Load on Surface Roughness, Residual Stress, and Deformation of Cold Forging Tools 査読

Karunathilaka, Tada, Uemori, Hanamitsu, Fujii, Omiya, Kawano

Metals 9 ( 7 ) 783 - 783 2019年7月

掲載種別：研究論文（学術雑誌）出版者・発行元：MDPI AG

Cold forging is a metal forming that which uses localized compressive force at room temperature. During the cold forging process, the tool is subjected to extremely high loads and abrasive wear. Lubrication plays an important role in cold forging to improve product quality and tool life by preventing direct metallic contact. Surface roughness and residual stress also greatly affects the service life of a tool. In this study, variations in surface roughness, residual stress, and specimen deformation with the number of cold forging cycles were investigated under different forging conditions. Specimens that were made of heat-treated SKH51 (59–61 HRC), a high-speed tool steel with a polished working surface, were used. The specimens were subjected to an upsetting process. Compressive residual stress, surface roughness, and specimen deformation showed a positive relationship with the number of forging cycles up to a certain limit and became almost constant in most of the forging conditions. A larger change in residual stress and surface roughness was observed at the center of the specimens in all the forging conditions. The effect of the magnitude of the forging load on the above discussed parameters is large when compared to the effect of the lubrication conditions.

DOI： 10.3390/met9070783

Web of Science

researchmap

純チタン薄板における微視的な不均一変形が表面あれに及ぼす影響に関する結晶塑性有限要素解析査読

材料 68 ( 6 ) 478 - 484 2019年6月

Springback Suppression of AZ31 Magnesium Alloy Sheet in Draw Bending at Elevated Temperature 査読

片平卓志, 上森武, 吉田哲哉, 瀧口三千弘, Komgrit Lawanwong, 吉田総仁

Key Engineering Materials Vol.794 127 - 132 2019年2月

Microscopic Elastic and Plastic Inhomogeneous Deformations and Height Changes on the Surface of a Polycrystalline Pure-Titanium Plate Specimen under Cyclic Tension 査読

Naoya Tada, Takeshi Uemori

Applied Sciences 8 ( 10 ) 1907 - 1907 2018年10月

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

A cyclic tensile test was carried out using a plate specimen of commercial pure titanium on a digital holographic microscope stage. Microscopic deformation of the grains was observed, and their height distribution was measured on the specimen surface. Each grain showed nanoscopic movement up and down, as well as reverse movement corresponding to specimen loading and unloading. We suggest that the different grain-specific changes in height were caused by microscopic inhomogeneities in the material, such as differences in the crystal orientation and geometries of both the surface and subsurface grains. Changes in grain height increased with tensile load, and a strong relationship was found between the height changes that occurred under elastic and plastic conditions. This suggests that microscopic plastic deformation is predictable from microscopic elastic deformation. In order to investigate the plastic deformation of grains in more detail, slip-line angles were measured after the tensile test. We found slip lines with similar angles in neighboring grains, suggesting that the plastic deformation of grains was not independent, but rather was related to that of surrounding grains and influenced by the deformation of subsurface grains.

DOI： 10.3390/app8101907

researchmap

Effect of Contact Pressure Applied on Tool Surface during Cold Forging on Fatigue Life of Tool Steel 査読

Nuwan Karunathilaka, Naoya Tada, Takeshi Uemori, Ryota Hanamitsu, Masahiro Kawano

Procedia Manufacturing 15 488 - 495 2018年

Cyclic stress and strain responses of AZ31 magnesium alloy sheet metal at elevated temperatures 査読

Takeshi Uemori, Takashi Katahira, Tetsuo Naka, Naoya Tada, Fusahito Yoshida

Procedia Manufacturing 15 1792 - 1799 2018年

Dimensional Changes of Graphite Flakes and Fracture in Tensile Tests of Gray Cast Iron 査読

Naoya Tada, Takeshi Uemori

Conference papers, ASME 2018 Pressure Vessels & Piping Conference PVP2018-85214 2018年

Elastic and Plastic Microscopic Undulation on the Surface of Polycrystalline Pure Titanium Under Tension 査読

Naoya Tada, Takeshi Uemori, Toshiya Nakata

JOURNAL OF PRESSURE VESSEL TECHNOLOGY-TRANSACTIONS OF THE ASME 139 ( 6 ) 1180 - 189 2017年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ASME

Commercial pure titanium has been widely used in the aerospace, chemical, and biomedical industries because of its light weight, high corrosion resistance, high strength, high heat resistance, and good biocompatibility. Pure titanium takes the form of a hexagonal closed-pack structure with anisotropic elasticity and plasticity, with most of its components being polycrystalline aggregates having different crystal orientations. Small mechanical loading under elastic conditions therefore always induces inhomogeneous microscopic deformation, and the resulting inhomogeneity brings about various defects such as inhomogeneous plastic deformation, microcracking, and necking. It is therefore important to investigate the microscopic inhomogeneous deformation under elastic and plastic conditions. In this study, a plate specimen of commercial pure titanium was subjected to a tensile test on the stage of a digital holographic microscope (DHM), and the microscopic deformation of grains in the specimen under elastic and plastic conditions were observed and measured. During the test, the grains' height distribution was measured in a fixed area on the specimen's surface at each tensile loading step, and the correlation between height distributions at different loads was examined. We found from the measurements that each grain shows a different height change even under elastic conditions with a small load. This inhomogeneous height change was enhanced as the load was increased to plastic conditions. A strong correlation between the height changes under elastic and plastic conditions was also found. This result suggests that the microscopic deformation experienced under plastic conditions is predictable from that observed under elastic conditions.

DOI： 10.1115/1.4038012

Web of Science

researchmap

Evaluation of Thin Copper Wire and Lead-Free Solder Joint Strength by Pullout Tests and Wire Surface Observation 査読

Naoya Tada, Takuhiro Tanaka, Takeshi Uemori, Toshiya Nakata

7 ( 8 ) 255 - 255 2017年8月

Time-Dependent Fracture of Copper-Cored Lead-Free Solder Ball and Nickel Rod Joints in Air, Distilled Water, and NaCl Solution 査読

Naoya Tada, Takeshi Uemori

IMPACT 2017 Proceedings 2017- 319 - 322 2017年

Description of closure of cyclic stress-strain loop and ratcheting based on Y-U model 査読

Fusahito Yoshida, Hiroshi Hamasaki, Takeshi Uemori

Key Engineering Materials 725 351 - 356 2017年

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 Ltd

This paper proposes a cyclic plasticity model to describe the closure of a cyclic stress-strain hysteresis loop based on the Y-U model. In this model, the backstress moves in a cyclic memory surface following a newly proposed kinematic hardening law. For this model just the same Y-U parameters can be used, and no additional material parameters are needed. By using a supplementary rule, this model is also able to describe ratcheting.

DOI： 10.4028/www.scientific.net/KEM.725.351

Scopus

researchmap

Effect of Hardening Rule for Spring Back Behavior of Forging 査読

Shinobu Narita, Kunio Hayakawa, Yoshihiro Kubota, Takafumi Harada, Takeshi Uemori

Procedia Engineering 207 167 - 172 2017年

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：Elsevier Ltd

Geometrical discrepancy between formed part and designed one is one of the major problems for metal forming processes. Spring back behavior is one of the most important factors on the discrepancy, in not only sheet metal forming but also cold forging process. For cold forging process, it is difficult to observe the change in geometry of forgings before and after release of tools/dies, since the workpiece during forging is covered by tools/dies in most cases. Uncertainty remains for the precision on geometrical prediction after spring back of the cold forged part. In the present research, the diameters of extruded shaft at the bottom dead center and after the release of tools/dies were measured to investigate the spring back behavior in the cold forging process. As a result of experiment, the diameter of extruded shaft was increased at the bottom dead center by spring back and decreased after the release by re-extrusion. For these series of change in diameter, FE analyses using isotropic and kinematic hardening models were performed in order to evaluate influence of spring back on the material hardening models in forging process. For kinematic hardening model, Yoshida-Uemori model modified for large strain region was employed. As a result of calculation, both the isotropic and kinematic hardening models showed the similar tendency on the change in diameter with the experimental one.

DOI： 10.1016/j.proeng.2017.10.756

Scopus

researchmap

Theoretical predictions of fracture and springback for high tensile strength steel sheets under stretch bending 査読

207 1594 - 1598 2017年

Asymmetric-shaped bending of adhesively bonded sheet metals 査読

Taro Tokuda, Takeshi Uemori, Tetsuya Yoshida, Michihiro Takiguchi, Fusahito Yoshida

Key Engineering Materials 725 630 - 635 2017年

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 Ltd

In sheet metal industries, press-formed sheet elements are usually adhesively bonded together at the final stage of assembly. Instead of such a conventional process, the present authors proposed a new technique that first flat sheets are adhesively bonded together and then press-formed into the final products [1]. In previous study, the problem of the die-bending (V-bending and hat-shaped bending) with symmetrical shape has studied. In this study, asymmetric-shaped bending of adhesively bonded sheet metals was investigated by experiments and FEM analysis method. In the case of asymmetric-shaped bending, it was found that the timing of contact from the die corner to the die hypotenuse is early in the press-forming process compared with symmetrical bending (V-bending and hat-shaped bending). For the FEM analysis results, the maximum shear strain in asymmetric-shaped bending was smaller than that in symmetric-shaped bending at the hat-shaped side. Thus, the shape of the die has a large influence on the die-bending of adhesively bonded sheet metals.

DOI： 10.4028/www.scientific.net/KEM.725.630

Scopus

researchmap

Influence of Bauschinger Effect and Anisotropy on Springback of Aluminum Alloy Sheets 査読

Takeshi Uemori, Satoshi Sumikawa, Tetsuo Naka, Ninshu Ma, Fusahito Yoshida

MATERIALS TRANSACTIONS 58 ( 6 ) 921 - 926 2017年

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

For accurate springback calculations, the development of accurate constitutive equation Yoshida-Uemori model must always be taken into account. However, several springback calculations of other sheet metals by Yoshida-Uemori model have shown wrong agreements with the corresponding experimental data. The reason is why most of them have been calculated from the view point of the accuracy of Bauschinger effect without the strong anisotropy of sheet metal. In the present paper, we have investigated how the initial anisotropy affects the amount of springback for aluminum sheet metals with Bauschinger effect. Specifically, hat bending experiments in R.D. and T.D. were compared with the corresponding calculations. From the above mentioned comparisons, we found that the optimum combination of an anisotropic yield functions and Yoshida-Uemori model is very important for accurate springback analysis.

DOI： 10.2320/matertrans.L-M2017812

Web of Science

researchmap

Cracking behavior of thin gold strip deposited on polycarbonate plate under Cyclic and stepwisely-increased tension 査読

Naoya Tada, Yafei Hu, Takeshi Uemori, Toshiya Nakata

108 01004 - 01004 2017年

　前のページ - 次のページ　

<上森 武>

論文 - 上森 武

<上森　武>

論文 - 上森　武