研究者業績

日下 正広

クサカ マサヒロ  (Masahiro Kusaka)

基本情報

所属
兵庫県立大学 大学院 工学研究科 機械工学専攻 准教授
学位
博士(工学)(*姫路工業大学*)
工学修士(*姫路工業大学*)

J-GLOBAL ID
200901090006014477
researchmap会員ID
1000057653

論文

 124
  • M. Kimura, Y. Kusumoto, M. Kusaka, K. Kaizu
    Journal of Materials Engineering and Performance 32(10) 4655-4667 2023年5月  
    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 2022年6月  
    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年  
    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.
  • 海津 浩一, 本岡 拓也, 日下 正広, 木村 真晃, 平井 三友
    日本機械学会論文集 88(907) 21-00313-21-00313 2022年  
  • Hirayama Akihiro, Kimura Masaaki, Kusaka Masahiro, Kaizu Koichi
    International Journal of Automation Technology 15(4) 388-395 2021年7月5日  
    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 2023年11月28日  査読有り
  • 前田 起樹, 海津 浩一, 日下 正広, 木村 真晃
    関西支部講演会講演論文集 2021.96 2602 2021年  
    自動車には交通事故による死傷者を減らすために安全技術が求められており,事故時の安全を確保するために衝撃吸収部材が搭載されている.この衝撃吸収部材が潰れ切るまでの変形量を大きくすることによって従来よりも衝突エネルギー吸収量を増加させるため,折り紙の一種であるミウラ折りを格子状に配したラティス構造体について,支柱の角度や直径を変更して衝撃圧潰解析により比較し,エネルギー吸収性能を検討した.
  • 大杉 泰征, 海津 浩一, 日下 正広, 木村 真晃
    関西支部講演会講演論文集 2021.96 2601 2021年  
    .空孔セルを有するクラッシュボックス側面にテーパを付けることで,荷重の変動を抑えることができたが,中間 部が緻密化していた.衝突エネルギー吸収量を増加させるため,クラッシュボックス上部から圧潰を進行させ変 位量を増やすことを狙いとし,①クラッシュボックスの高さを変更する②テーパの曲率を変更するという2点につ いて検討を行った.空孔セルを有するクラッシュボックス側面にテーパを付けることで,荷重の変動を抑えることができたが,中間 部が緻密化していた.衝突エネルギー吸収量を増加させるため,クラッシュボックス上部から圧潰を進行させ変 位量を増やすことを狙いとし,①クラッシュボックスの高さを変更する②テーパの曲率を変更するという2点につ いて検討を行った..
  • 森脇 貫氏, 海津 浩一, 日下 正広, 木村 真晃
    関西支部講演会講演論文集 2021.96 3905 2021年  
    ステントを半径方向に拡張した際に長軸方向に縮小してしまう問題に対して,半径方向に拡張したときに長軸方向にも展開できるステントを目的とし,折紙の折り方の1種であるなまこ折り形状を模擬したステントモデルを作成し,FEMを用いた円周の内側から外側に力を負荷させる解析し,血管内に留置されるステントの拡張の挙動について検討を行った.
  • 豊栖 遼, 海津 浩一, 木村 真晃, 日下 正広
    関西支部講演会講演論文集 2021.96 2604 2021年  
    スペースデブリの宇宙構造物への衝突に関して,宇宙構造物を防御するために設置される防御バンパーに注目し,防御バンパーをどのようにすればより耐衝撃性能が向上するのかを,三次元SPH解析を用いて検討を行った.

書籍等出版物

 4

講演・口頭発表等

 58

担当経験のある科目(授業)

 3

所属学協会

 2

共同研究・競争的資金等の研究課題

 12