真空浸炭処理したSCM420H切欠き材の回転曲げ疲労強度に及ぼすSP処理の影響

抄録

In order to investigate the effect of shot peening treatment on notched material, a rotating bending fatigue test was conducted on notched specimens made of vacuum-carburized SCM420H steel, with a stress concentration factor of approximately 1.76. In this study, four types of shot peening conditions were prepared: normal shot peening (SP), fine particle shot peening (FPP), super fine particle peening (SFPP) and double shot peening of SP and FPP (DSP). All shot peening treatments improved the fatigue limit to the same level as that of the non-peened smooth specimen. The internal stress distribution, accounting for both notch-induced stress concentration and residual stress, was investigated to examine the correlation between crack initiation behavior and fatigue limit. For SP treated specimens that do not undergo significant plastic strain, the fatigue limit can be explained by calculating the sum of applied load stress and residual stress, while considering the decay of residual stress. For DSP treated specimens that undergo significant plastic strain, it is difficult to explain the fatigue limit simply by calculating the sum of the applied load stress and residual stress; however, it can be explained based on the results of finite element analysis. Additionally, the fatigue properties of DSP-treated specimens were further enhanced by blast polishing.