機械工学科

南部 紘一郎

ナンブ コウイチロウ  (Koichiro NAMBU)

基本情報

所属
大阪産業大学 工学部 機械工学科 准教授
学位
博士(工学)(名城大学)

J-GLOBAL ID
201301098729162192
researchmap会員ID
B000232215

経歴

 4

論文

 40
  • 南部紘一郎, 國松龍弐
    ショットピーニング技術 36(3) 210-214 2024年9月  査読有り招待有り筆頭著者
  • 南部紘一郎
    Metal Finising News International 25 56-58 2024年5月  査読有り筆頭著者
  • Koichiro Nambu, Yusuke Saeki, Masahiro Okumiya
    Special issue of 28th IFHTSE 2023 Congress 2024年4月  
    Fine Particle peening is a method to obtain surface modification effects, such as fatigue strength improvement, by bombarding the work material with particles at high velocity. However, there are many factors that affect the surface modification effect, making it difficult to select the optimum conditions. The particle velocity and particle flight behavior have not been clarified due to the large number of flying particles in addition to the extremely high particle velocity. Therefore, in this study, in addition to air flow analysis inside and outside the nozzle, particle velocity analysis using the particle method was conducted. ANSYS was used for the airflow analysis, and Particle Works was used for the particle method. The nozzle diameter and nozzle-to-work distance were varied. The nozzle diameter was varied from 3 to 10 mm. The nozzle-to-work distance was 50, 100, and 150 mm. The pressure at the nozzle entrance was set to 0.2 MPa, and air flow analysis was performed under incompressible fluid conditions. The particle method used iron-based particles with a particle diameter of 100 μm as a model for analysis. The results of the airflow analysis showed that the potential core area increases as the nozzle diameter increases. This was attributed to the shear layer caused by the wall resistance inside the nozzle. Next, particle velocity analysis showed that particle velocity tended to increase with increasing nozzle diameter. In addition, it was found that the particle velocity increased with increasing nozzle-to-work distance. Next, the particle flight behavior was analyzed, and it was found that the particles accelerated most at the parallel part of the nozzle and continued to accelerate after the nozzle exit. Finally, to verify the validity of the analysis, the particle velocities were compared with those measured by a high-speed camera. Although the geometry of the nozzle was slightly different, the measured and calculated velocities showed similar trends, suggesting that the present method is valid.
  • Shogo Takesue, Keisuke Ono, Koichiro Nambu, Shoichi Kikuchi
    Fatigue and Fracture of Engineering Materials and Structures 2024年  
    Shot peening (SP) and fine particle peening (FPP) were performed as post-treatments on induction-hardened and tempered AISI 4140 steels. Furthermore, the combined effects of surface characteristics including changes in surface morphology, compressive residual stress, and hardness on the fatigue limit were quantitatively examined. The surface characteristics of the prepared specimens were investigated using a laser and stereomicroscope, a micro-Vickers hardness tester, and an X-ray device for residual stress measurements. The rotating bending fatigue properties were also examined. FPP increased the fatigue limit of induction-hardened and tempered steel samples by introducing compressive residual stress and increasing their surface hardness. Conversely, the fatigue limit of the steel treated with SP was lower than that of the electrochemically polished sample owing to the formation of large dents. The fatigue limits of post-peened induction-hardened and tempered steels can be estimated using a modified Goodman diagram considering changes in surface properties.
  • Satoru Ikeda, Koichiro Nambu
    Lecture Notes in Mechanical Engineering 123-128 2024年  
    In recent years, many problems have arisen, such as increased power consumption in commercial refrigerators due to water droplets on aluminum alloy surfaces, increased frost formation due to bacteria and mold, and increased transportation costs for bullet trains. To solve these problems, we turned our attention to surface texturing technology and shot blasting, a new surface component that can switch between hydrophobic and hydrophilic properties. Shot blasting can be applied to large areas at a lower cost than laser processing and can be used for surface texturing. This study reports the results of an evaluation of the effect of shot blasting on the surface wettability of aluminum alloys. Shot blasting was performed on aluminum alloy A5052 using various particles, and the wettability of the specimens was evaluated. It was found that the wettability after shot blasting varied with the particle material and particle size as in previous studies. Using the aspect ratio (dent depth/dent width) calculated from the surface roughness, it was found that the specimens became hydrophilic to hydrophobic up to an aspect ratio of 7 or less, and that the contact angle gradually increased to hydrophobic at an aspect ratio of 7 or greater.

MISC

 29
  • 南部 紘一郎
    Mechanical surface tech = メカニカル・サーフェス・テック : 表面改質&表面試験・評価の技術情報誌 (79) 32-34 2024年4月  
  • Shoichi Kikuchi, Keisuke Ono, Koichiro Nambu, Shogo Takesue
    28th IFHTSE 2023 Congress 2023年  
    In this study, low alloy steel (AISI4140) specimens with different surface morphology and hardness were prepared by shot peening and fine particle peening, followed by induction hardening and tempering at different temperatures. Rotating bending fatigue tests were performed at stress ratio of -1 for these specimens, and the combined effects of the surface dent formed by peening and residual stress on the fatigue limit of the induction hardened steels were quantitatively investigated. It was found that the fatigue limit of the induction hardened steel tended to decrease with an increase in the size of the particles used in the peening. This was because fatigue cracks were initiated at the surface dents formed by peening. The parameter of surface morphology that showed a good correlation with the fatigue limit of the induction hardened steel was the waviness parameter which is corresponded to the size of surface dens formed by peening, but not the roughness parameter. Furthermore, a fatigue limit estimation for induction hardened steels with different surface morphology and hardness was described using a modified Goodman diagram. The improvement in the fatigue limit of steels with surface dents due to compressive residual stress was more significant as the hardness decreased, and the maximum fatigue limit improved by compressive residual stresses increased as the size of surface dents decreased. In contrast, the maximum value of the compressive residual stress that contributes to the increased fatigue limit of steels tended to increase as the hardness increased.
  • Atsuya Watanabe, Takahisa Yamamoto, Koichiro Nambu, Yorinobu Takigawa
    28th IFHTSE 2023 Congress 2023年  
    Bulk nanocrystalline FeCoNi MEA with a high tensile strength was developed recently. Grain refinement is a hopeful approach to achieving excellent mechanical properties in HEAs/MEAs, however, the thermal stability of microstructure in the alloy has not been clarified enough. In this study, we investigated microstructure evolution in nanocrystalline FeCoNi MEA annealing at a 300-1000 °C temperature range. Sharp increases in the grain size were repeatedly found. Each plateau range formed respective orientations.
  • 奥宮正洋, 南部紘一郎
    熱処理 61(3) 76-81 2021年6月  
  • 南澤健太, 武末翔吾, 荒川仁太, 曙紘之, 南部紘一郎, 中村裕紀, 菊池将一
    日本機械学会M&M材料力学カンファレンス(CD-ROM) 2021 2021年  

講演・口頭発表等

 98

担当経験のある科目(授業)

 19

共同研究・競争的資金等の研究課題

 18

免許・資格

 2
  • 免許・資格名
    技術士(機械部門)
    取得年月日
    2021/06/17
  • 免許・資格名
    エックス線作業主任者
    取得年月日
    2020/05/18