金属の疲労強度に及ぼすShot-peeningの影響（第4報）腐蝕疲労に対する効果について

Abstract

It has been shown in our previous report that the surface stressing by shot-peening has a remarkable effect on the fatigue strength of steels and other metals having various types of surface weakness under non-corrosive atmosphere. In this paper, we examined the effect of shot-peening on the fatigue of Si-Mn steels under the corrosive atmosphere of distilled water and dilute H2SO4 solution. (1) The fatigue strength reduced under the atmosphere of distilled water was recovered considerably by shot-peening. For example,the fatigue limit at 107 cycles was increased from 36 kg/mm2 in the polished condition to 57 kg/mm2 in the shot-peened specimen,or about 58% in percentage. (2) In a dilute H2SO4 solution,the effect of shot-peening was reduced gradually in accordance with the increase of fatigue duration and of H2SO4 concentration,but it was still remarkable at short-time testing. (3) It was found from microscopic observation of the corrosion fatigued specimens that the propagation of fatigue cracks was prevented or delayed due to surface stressing, although the number of cracks in shot-peened specimens was much larger than in polished ones. Consequently, it is considered that the surface stressing by shot-peening is always effective in the view of prevention of fatigue failure under practical service condition which is usually accompanied by a somewhat corrosive atmosphere.