Estimation of high cycle fatigue limit of hard shot peened SUS316L by using the distributions of residual stress and hardness

摘要

Hard shot peening (HSP) treatment was very successful for the improvement of the high cycle fatigue strength of SUS316L steel. The improvement of the fatigue strength was caused by a hardening (a strain hardening) and a compressive residual stress of surface hardened layer which have a thickness of about 500μm, and was caused by change from surface crack origin fracture to subsurface crack origin fracture. In this study, the estimation of fatigue limit at about 10{sup}8 cycles was attempted byusing the hardness distribution, the HVB distribution and the residual stress distribution. By regarding the residual stress as the mean stress and by transforming from the HVB distribution to the fatigue strength or the tensile strength, the localfatigue strength distribution of HSP-treated SUS316L steel was calculated using the endurance fatigue limit diagram and the modified Goodman's diagram (the general method). As the result, fatigue limit at about 10{sup}8 cycles was not able to estimate bythese general method. But, from the proposal method with considering the stress intensity factor, the estimation of fatigue limit was fairly good coincident with the experimental fatigue limit.