南部 紘一郎

In order to determine the fine particle peening (FPP) conditions using particles of 10μm in diameter that could improve the fatigue strength, the hardness of FPP-treated specimens under different conditions was investigated. As results of hardness tests, the hardness of FPP-treated specimen under the condition of 30mm of nozzle distance which indicates the highest velocity of particles showed higher than that of one under the condition of 50mm of nozzle distance. Additionally, the hardness was increased with decreasing peening time. Furthermore, in order to clarify the effects of FPP using particles of 10μm on fatigue properties of A5056 aluminum alloy with three different peening time, fatigue tests were performed at room temperature using cantilever-type rotary bending fatigue testing machine. It was found that the fatigue strength was increased with decreasing peening time due to increasing surface hardness.

In this study, we proposed the creation of surface modification layer by ultra-fine particle peening process in order to achieve the development of high strength aluminum alloy. Therefore, we aim to clarify the effect of impact energy and surface modification by ultra-fine particle peening process. The analysis of collision energy was used for finite element analysis software LS-DYNA. Analysis conditions were set was particle of high speed steel and work of aluminum alloy. Results of the analysis, in the case with a constant amount of projection, the impact energy increases as the material is a small projection of the particle size was revealed

The most suitable condition that the fine crystal layer is produced and influence of the fine crystal layer on fatigue strength of SCM415 are examined. Generation of the fine crystal layer by FPB processing and the SP processing is reported in the past study. However, only a surface small portion can generate the fine crystal layer. In addition, it is hardly examined the influence that the fine crystal layer on fatigue strength. In this study, the most suitable condition that the fine crystal layer was produced throughout the surface was examined first. As a result, it was understood that strain rate and a projection rate influenced generation of the fine crystal layer. From this, it is thought that it is easy to generate fine crystal layer by lengthening projection time in small projection materials.

The FPB (Fine Particle Bombarding) process attracts attention as a new surface-preparation technique. The effect which the surface modification effect by this FPB process has on the fatigue strength of spring steel was investigated. It proved that surface roughness decreases and the hardness near surface rises rather than a shot peening process as compared with a shot peening process. As a result of comparing the shot time of a FPB process, hardness also increased as the shot time became long. The FPB process showed the value higher than a shot peening process by lowering of surface roughness, and the rise of hardness as a result of the fatigue test. These results showed that the FPB process was effective in the betterment in the fatigue strength of spring steel.