研究者業績

Masahiro Kusaka

  (日下 正広)

Profile Information

Affiliation
Associate Professor, Graduate School, of Engineering, Department of Mchanical and System Engineering, University of Hyogo
Degree
Doctor(Engineering)(Himeji Institute of Technology)
Master of engineering(Himeji Institute of Technology)

J-GLOBAL ID
200901090006014477
researchmap Member ID
1000057653

Papers

 124
  • M. Kimura, Y. Kusumoto, M. Kusaka, K. Kaizu
    Journal of Materials Engineering and Performance, 32(10) 4655-4667, May, 2023  
    In a previous study, the tensile strength of dissimilar friction welded joints that was composed between commercially pure Al (AA1070) and low carbon steel (LCS) decreased with increasing forge pressure. This result was not applicable to the general consequence of friction welding. To prevent a decrease in the tensile strength of joints by the increase in forge pressure, the improving method of tensile strength in friction welding was investigated. Two types of AA1070 with different tensile properties due to tempering condition were used, and the weld faying part of the specimen had various overhang lengths and weld diameters. Dissimilar friction welded joints, which were composed with those AA1070 side specimens and LCS specimens, were made with various forge pressures. Then, the relationship between the tensile strength of the joints and the forge pressure was evaluated. The tensile property of AA1070 base metals with various compression stresses was also investigated, and the result was compared with the tensile strength of joints. The decrease in the tensile strength of the friction welded joints with added high forge pressure, which had an AA1070 base metal fracture, could be prevented by changing of the shape at the weld faying part of the specimen and tempering condition of the AA1070 side. However, such a joint should be made with a suitable forge pressure with the AA1070 side fracture and the same tensile strength as that of its base metal since the consideration of the decrease in the tensile strength of joints by greater forge pressure can be ignored.
  • M. Kimura, Y. Sano, M. Kusaka, K. Kaizu
    Journal of Advanced Joining Processes, 5, Jun, 2022  
    The joint strength and its improvement of AA5083 Al alloy joints fabricated by friction stud welding method were investigated. The diameter of the work and stud side specimens were 32.0 mm and 12.8 mm, respectively, and those were friction welded. The appropriate welding condition for obtaining high tensile strength was established as follows: a friction speed of 17.5 s−1, a friction pressure of 80 MPa, a friction time of 1.6 s, and a forge pressure of 360 MPa. However, all joints fractured between the initial weld interface and the work or stud sides, i.e. the fracture did not occur in the base metal. It could be considered that the initial oxide film on the weld faying surface of the work side was not exhausted as the flash during the welding process. To obtain the joint having the fracture in the base metal, the suitable shape at the weld faying portion of the work side specimen was suggested as the groove shape. The inner diameter of the groove corresponded to the same diameter of the stud side, and that had a groove width of 3.0 mm with a groove depth of 1.0 mm. As a conclusion, AA5083 friction stud welded joint, which had the tensile strength of the base metal and the fracture in the base metal, could make with the appropriate welding condition. Furthermore, the weld faying portion at the work side should be in the suitable shape that urges the extrusion of the flash from this side.
  • Masaaki Kimura, Haru Saito, Masahiro Kusaka, Koichi Kaizu
    Welding International, 36(2) 114-127, 2022  
    This paper describes the stud shape and joint strength of low carbon steel joints fabricated by friction stud welding with low load force requirement. To reduce the load force during the welding process, the stud side with the circular hole at the weld faying surface part was used. The outer diameter of a cylindrically shaped stud side had 12.0 mm and that was welded to the circular solid bar with a diameter of 24.0 mm as the work side. The joint was made with a friction speed of 27.5 rps, a friction pressure of 60 MPa, and a forge pressure of 60 MPa, which was determined as the low force condition for obtaining good joint in the previous study. When joints were made by a cylindrically shaped stud with a hole diameter of 6.0 mm and its depth of 0.5 mm, all joints at a friction time of 0.6 s, i.e. the friction torque reached to the initial peak, had the same tensile strength as that of the base metal with the base metal fracture. All joints with flash from the initial weld interface had the fracture on the base metal, the bend ductility of over 15° with no cracking at the initial weld interface through an impact shock bending test, and a high fatigue strength of the base metal. That is, the sound joint could be successfully achieved, and that could be obtained with the same friction stud welding condition of the circularly shaped solid stud. As a conclusion, the joining technique for the friction stud welding method with low load force requirement was proposed in accordance with using a cylindrically shaped stud that has the circular hole with the shallow depth at the weld faying surface part.
  • KAIZU Koichi, MOTOOKA Takuya, KUSAKA Masahiro, KIMURA Masaaki, HIRAI Mitomo
    Transactions of the JSME (in Japanese), 88(907) 21-00313-21-00313, 2022  
    To reduce weigh of the transportation machines, joining of the FRP and the light metal is considered as important technique. In this study, the punching rivet method was applied to make joints between a GFRP sheet and an aluminum alloy A6061 sheet and joint strength was examined. The punching rivet method is possible to join the sheets without drilling by using a rivet and a rivet holder. The punching-out process of the sheets using a rivet shank as a punch and the joining process of the sheets using the rivet and the rivet holder are continuously performed. From the experimental results of joining of the GFRP sheet and the A6061 sheet, the joints made by the punching rivet method had no large crack and out-of-plane deformation of the joints was suppressed. From the results of the joint strength tests, the joints made by the punching rivet method had almost the same joint strength as the bolted joints which were tightened by regulated torque. In addition, the fatigue life of the joints made by the punching rivet method was longer than that of bolted joints. It could be confirmed that the punching rivet method was effective to join the GFRP sheet and the A6061 sheet.
  • Hirayama Akihiro, Kimura Masaaki, Kusaka Masahiro, Kaizu Koichi
    International Journal of Automation Technology, 15(4) 388-395, Jul 5, 2021  
    The microstructure and mechanical properties of the AlSi12CuNi alloy fabricated by the additive manufacturing technique, laser powder bed fusion (L-PBF), were investigated. Several laser irradiation conditions were examined to optimize the manufacturing process to obtain a high volume density of the fabricated alloy. Good fabricated samples with a relative density of 99% or higher were obtained with no cracks. The fabricated samples exhibited significantly good mechanical properties, such as ultimate tensile strength, breaking elongation, and micro-hardness, compared to the conventional die casting AlSi12CuNi alloy. Fine microstructures consisting of the α-Al phase and a nano-sized eutectic Al-Si network were observed. The dimensions of the microstructures were smaller than those of the conventional die-casting AlSi12CuNi alloy. The superior mechanical properties were attributed to the microstructure associated with the rapid solidification in the L-PBF process. Furthermore, the influence of the building direction on the mechanical properties of the fabricated samples was evaluated. The ultimate tensile strength and breaking elongation were significantly affected by the building direction; mechanical properties parallel to the roller moving direction were significantly better than those perpendicular to the roller moving direction. In conclusion, AlSi12CuNi alloys with good characteristics were successfully fabricated by the L-PBF process.

Misc.

 264
  • 木村 真晃, 杉山 和輝, 日下 正広, 海津 浩一, 高橋 剛, 武田 海成
    溶接構造シンポジウム2023講演論文集, 538-545, Nov 28, 2023  Peer-reviewed
  • Maeda Tatsuki, Kaizu Koichi, Kusaka Masahiro, Kimura Masaaki
    The Proceedings of Conference of Kansai Branch, 2021.96 2602, 2021  
    Automobiles are highly convenient and indispensable as a means of transportation in our lives, however traffic accidents are an important issue and casualties must be significantly reduced. Technology for automobile safety is required to reduce casualties caused by traffic accidents, and impact energy absorbing members, such as a crash box and a side member, are used to protect occupants in the event of an accident. These members are required to be lightweight in order to improve running distanse and be required to absorb more impact energy. The crash box requires the ability to suppress load fluctuations, and has high strength and large deformation to improve the impact energy absorption performance. In this study, the shapes of lattice structure imitating Miura-ori, which is a kind of origami, were examined with the aim of increasing the amount of impact energy absorbed by increasing the amount of deformation. From results obtained by the impact crushing analysis, it was found that lattice structures imitating Miura-ori with appropriate strut angles and diameters have small load fluctuations and excellent impact energy absorption performance.
  • Osugi Taisei, Kaizu Koichi, Kusaka Masahiro, Kimura Masaaki
    The Proceedings of Conference of Kansai Branch, 2021.96 2601, 2021  
    Researches on crash boxes for automobiles are being carried out to reduce occupant damage caused by traffic accidents. We have been studying a crash box consisting of many cells with an elliptical hole for the purpose of improving energy absorption by increasing the amount of displacement during crushing. Our previous studies have showed that the tapers on the side plane of the crash box reduces load fluctuations, however the densification comes from middle part of the crash box. In this study, models that crushed from the impact face of the crash box were examined to reduce damage to the side members connected to the crash box. In addition, by comparing the performance of a crash box model consisting of cells with a circular hole and a crash box model with an elliptical hole, it was clarified that the crash box consisting of cells with elliptical holes had a large crushing displacement and was excellent in impact energy absorption.
  • MORIWAKI Kanji, KAIZU Koichi, KUSAKA Masahiro, KIMURA Masaaki
    The Proceedings of Conference of Kansai Branch, 2021.96 3905, 2021  
    A stent is a tubular network that is placed inside a blood vessel to support the narrowing of the blood vessel and keeps the blood vessel in an expanded state. The stent needs to have high extension rate since the stent is attached to the tip of the catheter and is carried through the blood vessel to the affected part. Our propose of this study is to develop a stent that can be expanded in the radial and longitudinal directions. We created a stent model imitating the Namako-ori, which was a type of folding origami, and analyzed the expansion behavior of the stent using FEM analysis. From the analysis results, it was confirmed that the proposed stent model could be extended in the radial and longitudinal directions.
  • TOYOSU Ryo, KAIZU Koichi, KIMURA Masaaki, KUSAKA Masahiro
    The Proceedings of Conference of Kansai Branch, 2021.96 2604, 2021  
    In recent years, space debris has been on the increase. Space debris orbits around the earth at a maximum speed of 15 km/s(1). If space debris collides with a space station, it will cause enormous damage. Therefore, countermeasures against space debris collisions are indispensable for advancing space development. The purpose of this study is to clarify how the defending performance of the bumper shield can be improved to reduce damage to the space structure. Reimerdes et al.(4) showed that it was advantages to halve the thickness and install two bumpers than to install one bumper. In this study, the defending performance of the bumper shield in which one bumper was divided into plural bumpers in the thickness direction and those bumpers were arranged was examined by using SPH analysis. In addition, the bumpers with protrusions were examined to scatter fragments of debris and bumpers. From analysis results, it was found that the defending performance of the bumper shield was improved as the number of bumpers increased. The method of scattering fragments of debris and bumpers was effective for improving the defending performance. It was also found that the defending performance of the bumper with protrusions depended on the place where debris collided with the bumper. Therefore, it is considered that bumpers with protrusions are less reliable than flat bumpers. It is necessary to consider an effective method for scattering debris.

Books and Other Publications

 4

Presentations

 58

Teaching Experience

 3

Professional Memberships

 2

Research Projects

 12