Abstract
The authors investigated the surface refined characteristics and fatigue strength of NH materials treated by Double Shot Peening (DSP) and Stress Double Shot Peening (SDSP). The results oblation : (1) High hardness of 383HV by DSP (2) Large maximum compressive residual stress with -733MPa of the NH+DSP material (3) Increased fatigue limit of the NH+DSP material. 33%(stress ratio R=0) and 28% (R=-1) higher fatigue limit than the NH materials, respectively. And considerably increased fatigue limit of the NH+SDSP material. 58% (stress ratio R=0) and 39% (R=-1) higher fatigue limit than the NH materials, respectively. (4) There is proportionality relation between mean stress and amplitude stress is R=0. However, there is no it in R=-1.
