ショットピーニング方法の違いによる材料硬さと残留応力分布と降伏応力の関係

抄録

Shot peening technology plays a very important role in improving the fatigue strength of springs. Until now, many studies were carried out to make clear on relationship between shot peening and fatigue, or to estimate residual stress theoretically. In this paper, it investigated relationship among specimen's hardness, residual stress distribution and yield stress on the difference of shot peening methods. The material used was SUP9, and the hardness was from 308HV to 746HV, prepared by quenching and tempering. Shot peening methods used were single shot peening (SP), double shot peening (DSP), and stress double shot peening (SDSP) . The compressive residual stress obtained by shot peening tends to increase in proportion with increasing specimen's hardness. DSP has a large effect to increase the compressive residual stress of surface for the all hardness of specimen. It can be realized that SDSP can be obtained the deeper and larger compressive residual stress for the all hardness of specimen. The ratio of residual stress that can be obtained for yield stress of specimen is about 50%in case of SP and DSP, and is 83% in case of SDSP. Further it can be estimated that residual stress and yield stress become the same value in case of SDSP by simple tension.