研究者詳細 - 岡田　晃

論文 - 岡田　晃

分割表示 396 件中 141 - 160 件目／全件表示 >>

Influence of Jet Flushing on Corner Shape Accuracy in Wire EDM 査読

Tomonori Ebisu, Akiyoshi Kawata, Yasuhiro Okamoto, Akira Okada, Haruya Kurihara

Procedia CIRP 68 104 - 108 2018年4月

Magnetic fixtures for enhancement of smoothing effect by electron beam melting 査読

Togo Shinonaga, Akira Okada, Hao Liu, Mitsuhiro Kimura

Journal of Materials Processing Technology 254 229 - 237 2018年4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：Elsevier Ltd

In large-area electron beam (EB) irradiation method developed recently, high energy density EB can be obtained without focusing the beam. Therefore, large-area EB of 60 mm in diameter can be used for instant melting and evaporation of the wide area material surface, and high efficient surface finishing is possible. However, if the workpiece has a hole shape, the EB concentrates in the entrance edge or inside wall of the hole. Thus, it is difficult to smooth the hole bottom surface. Previous study showed that the surface smoothing and micro-deburring effects for non-magnetic workpiece could be improved by setting a magnetic block under the workpiece, since the electrons tend to concentrate the magnetic block along magnetic lines. In this study, smoothing of hole bottom surface was experimentally investigated by setting a magnetic block under a workpiece in large-area EB irradiation. Expansion of smoothing area of the bottom surface was also tried by setting a through hole at the center of the magnetic block. It was clarified that wide area of hole bottom surface could be smoothed by large- area EB irradiation by setting the magnetic block under workpiece. The surface roughness decreased to less than 3.0 μmRz at the area of hole bottom surface. When the hole diameter was 20 mm and hole depth was less than 40 mm, smoothing area of 10 mm in diameter was obtained by using the magnetic block. Moreover, the smoothing area was sufficiently expanded by setting a through hole with an appropriate diameter in magnetic block.

DOI： 10.1016/j.jmatprotec.2017.11.024

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Mold Releasability of EDM Finished Surface Using Powder Mixed Working Fluid 査読

Ryoji Kitada, Keita Fujii, Ruixiang Wang, Akira Okada

International Journal of Electrical Machining ( 23 ) 24 - 31 2018年3月

Influence of Pulse Duration on Effective Energy on Material Removal in Micro-processing of Mild Steel by Several Hundred Nanoseconds Pulsed Laser 査読

Yasuhiro Okamoto, Mizuna Ito, Akira Okada, Togo Shinonaga

International Journal of Electrical Machining ( 23 ) 38 - 44 2018年

Study on Variation of Burr Height in Micro-deburring with Large-area Electron Beam 査読

Togo Shinonaga, Tsubasa Sakai, Yasuaki Kimura, Akira Okada

International Journal of Electrical Machining ( 23 ) 45 - 50 2018年

Influence of material property on thickness of modified layer generated by large-area electron beam 査読

Togo Shinonaga, Yasuaki Kimura, Tsubasa Sakai, Akira Okada

19TH CIRP CONFERENCE ON ELECTRO PHYSICAL AND CHEMICAL MACHINING 68 178 - 183 2018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 SCIENCE BV

In large-area electron beam (EB) irradiation method developed recently, high energy density of EB can be obtained without focusing the beam. Therefore, the wide area of material surface can be melted instantly, and high efficient surface finishing is possible. Moreover, surface functions such as corrosion resistance and water repellency of the metal molds were improved by the large-area EB irradiation, since thin resolidified layer was formed on the metal surface. It is expected that thick modified layer is effective to maintain their surface functions for long-term. Therefore, control and prediction of the modified layer thickness are important in order to obtain appropriate modified layer thickness on metals with different material properties. In this study, variations of modified layer thickness on metals with different material property are experimentally investigated. Furthermore, electron behavior during large-area EB irradiation is simulated by using an electron track analysis, and prediction of the modified layer thickness is tried with temperature distributions by using an unsteady heat conduction analysis. Experimental results show that the modified layer thickness increases with increasing energy density. The thickness with high relative permeability is larger than that with low one. Analytical results of the modified layer thickness in unsteady heat conduction analysis show quantitative agreement with experimental ones. Furthermore, the modified layer thickness on the metals with different thermal property and density is also discussed. Then, the modified layer thickness of metals with different material property can be predicted by using our unsteady heat conduction analysis model. (C) 2018 The Authors. Published by Elsevier B.V.

DOI： 10.1016/j.procir.2017.12.043

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Effects of Polarization Direction on Removal Characteristics of Silver Nanowire Transparent Conductive Film by Ultrashort Pulsed Laser 査読

T. Shimose, Y. Okamoto, M. Oshita, N. Nishi, T. Shinonaga, A. Okada

Journal of Advanced Mechanical Design, Systems, and Manufacturing 12 ( 5 ) JAMDSM0100-1 - JAMDSM0100-5 2018年

Fundamental Study on Addition of Osteoconductivity to Titanium Alloy Surface by EDM 査読

Togo Shinonaga, Yuta Iida, Ryota Toshimitsu, Akira Okada

International Journal of Automation Technology 11 ( 6 ) 869 - 877 2017年11月

Influence of Nozzle Jet Flushing on Wire Breakage in 1st-Cut Wire EDM from Start Hole 査読

Akiyoshi Kawata, Akira Okada, Yasuhiro Okamoto, Haruya Kurihara

Key Engineering Materials 749 45 - 50 2017年9月

Effects of Pulse Duration on Removal Characteristics of Silver Nanowire Transparent Conductive Film by Nanosecond Pulsed Laser 査読

Norio Nishi, Yasuhiro Okamoto, Masafumi Oshita, Akira Okada, Togo Shinonaga, Tomokazu Sakagawa

Journal of Materials Processing Technology 240 255 - 261 2017年2月

Improvement of curved hole EDM drilling performance using suspended ball electttrode by workpiece vibration 査読

A.Okada, A. Yamacuchi, K. Ota

CIRP Annals ?Manufacturing Technology 66 ( 1 ) 189 - 192 2017年

Study on clarification of large-Area eb irradiation phenomenon by electron track analysis 査読

Yasuaki Kimura, Togo Shinonaga, Akira Okada

Key Engineering Materials 749 ( 749 ) 118 - 123 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 large-Area electron beam (EB) irradiation method, uniformly high energy density can be obtained without focusing the beam. Large-Area EB can be used for melting and evaporating metal surface instantly. It was clarified that high efficient surface finishing of metal mold steels, ceramics and cemented carbides was possible by the large-Area EB irradiation. Furthermore, the tip of convex shape was often rounded after large-Area EB irradiation with remarkable material removal at the tip. This phenomenon is probably caused due to the heat accumulation and electrons concentration at the tip. However, electrons behavior near the workpiece surface during large-Area EB irradiation has not yet been clarified. In this study, electron track analysis was conducted in order to clarify electrons behavior during large-Area EB irradiation. At first, analytical model of the large-Area EB irradiation apparatus was built. Then, the EB diameter on the workpiece surface was experimentally measured with different energy density in order to evaluate the accuracy of our analytical model. The calculated results of EB diameter were in good agreement with the experimental ones. In addition, the electrons concentration phenomenon at the tip of convex shape was clarified by calculating energy density distribution on the surface obtained with electron track analysis. The analytical results indicated that the energy density increased from edge to tip of convex shape, while the energy density was constant in the case of planar shape. Experimented results also showed that removal thickness increases with high relative permeability. These results were similar tendency to the energy density distribution. Therefore, electrons concentration on the tip could be simulated by the electron track analysis.

DOI： 10.4028/www.scientific.net/KEM.749.118

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Influence of nozzle jet flushing on wire breakage in 1st-cut wire edm from start hole 査読

Akiyoshi Kawata, Akira Okada, Yasuhiro Okamoto, Haruya Kurihara

Key Engineering Materials 749 ( 749 ) 130 - 135 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 wire EDM (electrical discharge machining) process, it is important to smoothly exclude debris and bubbles generated in the working gap for keeping stable performance. Much debris stagnation in the gap would cause frequent occurrence of discharge concentration and secondary discharge, which results in unstable machining performance, such as frequent wire breakage, low removal rate, and low shape accuracy. Therefore, a jet flushing of working fluid using upper and lower jet nozzles has been conventionally applied for excluding the debris and bubbles from the machined kerf. Nevertheless, it is well known that the wire often breaks when the machined kerf length is a few mm from the start hole in 1st-cut wire EDM. The influence of machined kerf length on the flow field, the debris exclusion, and the wire behavior caused with hydrodynamic force by the jet flushing should be made clear. In this study, variations of flow field in the kerf, the debris accumulation state and the wire deflection caused jet flushing with machined length were analytically investigated by CFD (computational fluid dynamics) and structural analysis when 1st-cut wire EDM was done from a small start hole. Moreover, the effects of machined kerf length on the wire deflection and wire breakage were discussed. Wire breakage frequency experiments showed that wire tended to frequently break at a certain machined kerf length, where the wire deflection rapidly increased and the debris residence time in the gap became long.

DOI： 10.4028/www.scientific.net/KEM.749.130

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Study on Reduction of Discoloration Area in Micro-drilling of Multi-layered Artificial Skin by Picosecond Pulsed Laser 査読

Yasuhiro Okamoto, Akira Eguchi, Naoto Maeda, Akira Okada, Shogo Minagi, Qiuyue Pan, Keiji Jin, Goro Nishigawa

International Journal of Electrical Machining ( 22 ) 8 - 13 2017年

Improvement of Surface Characteristics for Long Life of Metal Mold by EDM in Chromium Powder MixedWorking Fluid. 査読

Ruixiang Wang, Ryoji Kitada, Ryota Toshimitsu, Akira Okada

International Journal of Electrical Machining ( 22 ) 26 - 30 2017年

Cutting Performance of Boron-doped Diamond Coated Tools in Drilling of CFRP 査読

Alexander SOLDATOV, Akira OKADA, Kensuke UEMURA, Hitoshi OGAWA

Proceedings of the 9th International Conference on Leading Edge Manufacturing in 21st Century (LEM21), B13 B13 2017年

Influence of Pulse Duration on Effective Energy on Material in Nanosecond Pulsed Laser Processing of Mild Steel 査読

Mizuna Ito, Togo Shinonaga, Yasuhiro Okamoto, Akira Okada

Proceedings of the 9th International Conference on Leading Edge Manufacturing in 21st Century (LEM21), D10 D10 2017年

Effects of Polarization Directionon Removal Characteristics of Silver Nanowire Transparent Conductive Film by fs Pulsed Laser 査読

Takahiro Shimose, Yasuhiro Okamoto, Masafumi Oshita, Norio Nishi, Togo Shinonaga, Akira Okada

Proceedings of the 9th International Conference on Leading Edge Manufacturing in 21st Century (LEM21), D09 D09 2017年

Study on Shape Variation of Periodic Surface Nanostructures Produced with Ultrashort Pulse Laser for Control of Cell Spreading Direction 査読

Shono Kinoshita, Togo Shinonaga, Yasuhiro Okamoto, Akira Okada

Proceedings of the 9th International Conference on Leading Edge Manufacturing in 21st Century (LEM21), D07 D07 2017年

Low-visibility Processing of Silver Nanowire Transparent Conductive Film by Pulsed Laser 査読

Yasuhiro Okamoto, Norio Nishi, Masafumi Oshita Takahiro, Shimose,Togo Shinonaga, Akira Okada, Tomokazu Sakagawa

Proceedings of 36th International Congress on Applications of Lasers & Electro-Optics 2017, M202 M202 2017年

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