Effects Of Shot Peening On Torsional Fatigue Strength Of High Strength Spring Steel In Air And Corrosive Environment

Author:  M. Wakita, T. Kuno, T. Hasegawa, K. Saruki, K. Tan
Source:  Conf Proc: ICSP-10 Tokyo, Japan 2008
Doc ID:  2008092
Year of Publication:  2008
Abstract:  
ABSTRACT Torsional fatigue tests were conducted for spring steels,SUP7 prepared in the heat treatment, whose Vickers hardness was 480. The effects of the shot peening on the fatigue strength in the corrosive environment and air were studied. The effect of shot peening for the smooth specimens on the fatigue strength in air were comparatively small. This was considered to be caused by the decrease of the residual stress during the fatigue strength test and the effect of the surface roughness by the shot peening was small. On the other hand, the effect of the shot peening for the smooth specimens with artificial pits on increasing the fatigue strength in air was large. And the effect of the shot peening for the smooth specimens on the fatigue strength in the corrosive environment was remarkably large, except for the case of short fatigue life. This was considered to be caused by the residual stress from shot peening, preventing the crack initiation from corrosion pit or crack propagation. KEY WORDS Torsional fatigue, Spring steel, Shot peening, Corrosive environment, S-N curve