Papers by Author: Kenzo Fukaura

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Authors: Yasunori Harada, Makoto Fukunaga, Kenzo Fukaura, Satoru Ujihashi, Yuji Kobayashi
Abstract: The butt joining of dissimilar sheets using a shot peening process was investigated. Shot peening is a surface treatment and improves the performance of engineering components. In shot peening, the substrate undergoes a large plastic deformation near its surface due to a hit with many shots. Thus, plastic flow characterized by a shear droop occurs at the edge of the substrate due to shot peening. When the dissimilar sheets with the edge of the notch geometry are connected without level difference and shot-peened the connection, the sheets can be joined due to the plastic flow generated by the large plastic deformation during shot peening. In the experiment, a compressed-air-type shot peening machine was employed. The influences of processing conditions on the joining of the dissimilar sheets were examined. The joint strength increased with the kinetic energy of shots. It was found that the present method using shot peening process was effective in joining dissimilar sheets.
843
Authors: Yasunori Harada, Kenzo Fukaura, Kenichiro Mori
Abstract: In the multi-stage deep drawing processes of a beta titanium alloy sheet, the formability has been investigated. The beta titanium alloy sheets have sufficient ductility at room temperature, whereas a seizure tends to occur during deep drawing due to high reactivity with other materials. To prevent the seizure, the beta titanium alloy sheet was treated by oxide coating heating, because the coated sheet was not in direct contact with the die during deep drawing due to the existence of the oxide layer. The blank used was the commercial beta titanium alloy Ti-15V-3Cr-3Sn-3Al. The effect of the coating condition on the formability in the multi-stage deep drawing process was examined. It was found that long drawn cups with a height sixfold that of the diameter were successfully formed by oxide coating heating.
121
Authors: Yasunori Harada, Kenzo Fukaura, Noriyuki Tsuchida
Abstract: In this study, the grain refinement near the surface of metal workpiece using hot shot peening was investigated to improve the surface properties of the workpiece. In this process, the grains were refined due to plastic deformation generated by the collision of a lot of shots under hot working conditions. A model experiment using two shots was carried out to examine the effects of the amount of deformation, the processing temperature and the time interval of the collision on grain size. In the experiment, the workpieces were stainless steel SUS304 and commercially pure copper. It was found that the global surface layer successfully attained to the fine grains by means of hot shot peening.
1080
Authors: Yasunori Harada, Kenzo Fukaura, Toshinori Aoki, Daien Yokoi, Yasushi Haruna
Abstract: Shot peening is a surface treatment and improves the performance of engineering components. More recently, a new type of microshot has been developed to enhance peening effect. In the present study, the influence of microshot peening on the surface layer characteristics of cold tool steel was investigated. In the experiment, the microshot peening apparatus with a heating furnace was produced experimentally. The projective method of the microshot was a compressed air type. The peening microshots of 0.1mm diameter were cemented carbide and the workpiece was commercially cold tool steel SKD11. Surface roughness, compressive residual stress, and hardness in the peened workpiece were measured. The effect of microshot peening on the fatigue strength of cold tool steel was also examined. The use of hard microshot such as cemented carbide was found to cause a significantly enhanced peening effect for cold tool steel.
897
Authors: Yasunori Harada, Kenzo Fukaura, Dae Gi Kim
Abstract: A lining process for carbon steel using shot peening was investigated. In the shot peening experiment, the dissimilar foil set on the carbon steel substrate is pelted with many shots at a high velocity. The foil is bonded to the surface of the substrate due to plastic deformation induced by the collision of the shots. In the experiment, an air-type shot peening machine with an electrical heater was employed. The substrates are commercially carbon steel S45C, and the foils are commercially pure aluminum, pure copper, and pure nickel. The effects of shot conditions and the heating temperature on the joinability were examined. To improve surface characteristics such as wear resistance and corrosion resistance, the surface alloying of the lined workpiece was also attempted. The metal foils were successfully joined to the surface of the substrate. It was found that surface properties of carbon steel could be improved by the shot lining process.
853
Authors: Midori Komada, Yoshikazu Kuroda, Ryo Murakami, Noriyuki Tsuchida, Yasunori Harada, Kenzo Fukaura, Shingo Fukumoto
Abstract: Microstructure and mechanical properties of high nitrogen steels whose chemical composition were Fe-17Cr-12Mn-3Mo and that was produced by using metal injection molding method and nitrogen absorption methods were examined. A compact which is furnace cooled from 1573 K has a brittle surface layer with high chromium and nitrogen contents but the surface layer disappears when the compact is held at 1473 K. The compact which is furnace cooled at 1473 K is observed precipitates in the grains and the grain boundary, while the compact which is quenched at 1473 K shows homogeneous microstructure. In the heat treatments at 1473 K for 2, 5, and 10 h, the nitrogen content becomes higher with increasing of holding time. In the holding times of 5 and 10 h, the microstructure is austenite. In the tensile tests, tensile strength becomes larger with increasing of nitrogen content. In the specimen which is conducted the heat treatment at 1473 K for 10 h, tensile strength is about 1,000 MPa and elongation is 80 %, which shows better balance of strength and elongation than SUS304 and SUS316 steels.
19
Authors: Yoshikazu Kuroda, Midori Komada, Ryo Murakami, Shingo Fukumoto, Noriyuki Tsuchida, Yasunori Harada, Kenzo Fukaura
Abstract: Ni-free austenitic steels containing high nitrogen have been developed to protect against earth resource. High nitrogen steels (HNS) have a lot of advantages, e.g., HNS have high strength, corrosion resistance, toughness, work hardening rate and large rocking parameter in the Hall-Petch equation. On the other hand, it is difficult to fabricate HNS by IM method under 0.1 MPa and to work at room temperature. We have tried to make HNS by combined use of metal injection molding method (MIM) and nitrogen absorption method. Powder compositions used was Fe-17Cr-12Mn-3Mo.The benefit of this method is to make metal parts in near net shape. In order to use this method, we should know the sintering heat schedule, timing for introducing nitrogen gas, gas pressure and setter material etc. Therefore, the shrinkage rate, density and the solution-treated microstructure of MIM compacts were examined to find out the optimum conditions.
15
Authors: Ryo Murakami, Yousuke Aoyama, Noriyuki Tsuchida, Yasunori Harada, Kenzo Fukaura
37
Authors: Yasunori Harada, Kenzo Fukaura
Abstract: In this study, plastic flow joining using a shot peening process was investigated. Surface treatment is necessary to improve the surface properties. Shot peening is one of the surface treatments. Since the surface of substrate is hit repeatedly with a large number of shots, the substrate undergoes a large plastic deformation near its surface. Therefore, plastic flow characterized by a shear droop occurs at the edge of the substrate due to shot peening. If an implant made of a dissimilar material is set in a hollow space on the surface of the substrate and then shot-peened, it can be joined to the substrate due to the peening droop generated by the large plastic deformation during shot peening. In this method, the availability of the plastic flow, i.e., the peening droop makes the joining of the implant possible. In the experiment, a compressed-air-type shot peening machine was employed. To examine experimentally the influence of working temperature on bondability, equipment with a heating furnace was produced. The influence of processing conditions on the joining of the implant and the substrate was examined. The joint strength increased with the kinetic energy of shots and processing temperature. The improved implant with a step was effective in improving in bondability. The dissimilar material was also successfully joined to a thin sheet by using of the interaction of peening droops. It was found that the present method using the peening droop was effective for joining the dissimilar materials.
865
Authors: Yasunori Harada, T. Murao, Kenichiro Mori, Noriyuki Tsuchida, Kenzo Fukaura
Abstract: In this study, deep drawing using plastic die was investigated to prevent seizure during forming. In the deep drawing process of aluminum and titanium sheets, seizure was found to occur during forming due to a high reactivity with other metals. For the prevention of seizure, plastic dies were used in this study. These plastic materials have a good resistant to seizing, since no seizure occurs in the contact surface of the metal and plastic material. Moreover, the effects of seizure and wearing die on the dimensional accuracy of drawn cups were examined using nylon die. The blanks used were pure aluminum, aluminum alloy A5052 and pure titanium. The blanks could be successfully formed with a water lubricant. To increase the dimensional accuracy of the drawn cups, deep drawing using fiber-glass-reinforced nylon and plastic composite steel die was also attempted. It was found that the use of plastic die was very effective in preventing of seizure.
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