研究者詳細 - 多田　直哉

論文 - 多田　直哉

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Prediction of the Fracture Location by Tensile Tests of Gray Cast Iron Based on the Dimensional Changes of Graphite Flakes 査読

Naoya Tada, Takeshi Uemori, Junji Sakamoto

Journal of Pressure Vessel Technology 143 ( 2 ) 2021年4月

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 PVP2020-21715 2020年10月

Finite element study of the effect of internal cracks on surface profile change due to low loading of turbine blade 査読

Junji Sakamoto, Naoya Tada, Takeshi Uemori, Hayato Kuniyasu

Applied Sciences (Switzerland) 10 ( 14 ) 4883 2020年7月

短繊維強化複合材料の可視化データによる破壊予測技術査読

多田直哉

プラスチックエージ 66 ( 799 ) 53 - 56 2020年3月

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

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積層セラミックコンデンサのプレス変形挙動査読

成瀬文雄, 多田直哉

FCレポート，日本ファインセラミックス協会 38 ( 1 ) 30 - 34 2020年1月

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) ( 19-402 ) 2019年10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

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

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

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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) PVP2019-93546 2019年7月

担当区分：筆頭著者記述言語：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：American Society of Mechanical Engineers

<title>Abstract</title>
Composite materials such as carbon-fiber-reinforced plastics (CFRP) and glass-fiber-reinforced plastics (GFRP) have been attracting much attention from the viewpoint of lightweight solution of automobiles and airplanes. However, the recyclability of these composite materials is not sufficient and the environmental load is large. Recently, self-reinforced polymer (SRP), in which similar polymer is used for reinforcing fibers and matrix, has been proposed. High-density polyethylene (HDPE) reinforced with ultra-high-molecular-weight polyethylene (UHMWPE) fibers, so-called self-reinforced PE (SRPE), is one of the promising thermoplastic composites. In this study, SRPE plates were made and the tensile tests were carried out. After the effect of reinforcement of UHMWPE fibers was evaluated on the basis of the tensile strength, the relationship between the distribution of UHMWPE fibers and the location of the final fracture line was examined. It was found from these experimental results that the fracture tends to occur along the regions with low area fraction of fibers or along those with low area fraction of fiber/matrix boundaries. This fact suggests that the fracture location of SRPs is predictable from the distribution of reinforcing fibers.

DOI： 10.1115/pvp2019-93546

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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

上森武, 柿原大毅, 多田直哉

材料 68 ( 6 ) 478 - 484 2019年6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

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 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

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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

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 Strain Resposes of AZ31 Magnesium Alloy Sheet Metal at Elevated Temperature 査読

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

Procedia Manufacturing 15 1792 - 1799 2018年

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

Naoya Tada, Takeshi Uemori, Toshiya Nakata

Transactions of the ASME, Journal of Pressure Vessel Technology 139 ( 6 ) 061403 2017年12月

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

Crystals 7 ( 8 ) 255 - 255 2017年8月

Springback analysis of aluminum alloy sheet metals by yoshida-uemori model 査読

Takeshi Uemori, Kento Fujii, Toshiya Nakata, Shinobu Narita, Naoya Tada, Tetsuo Naka, Fusahito Yoshida

Key Engineering Materials 725 566 - 571 2017年

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 319 - 322 2017年

Tensile Test of Copper-Cored Lead-Free Solder Joints Using Non-Contact Type Testing Device with Permanent Magnets 査読

N. Tada, T. Uemori, T. Nakata

SEM Annual 2017 Proceedings 478 - 478 2017年

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

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

Procedia Engineering 207 1594 - 1598 2017年

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