レーザキャビテーションの圧潰衝撃力を援用した機械的表面改質によるステンレス鋼の疲労強度向上

抄録

In the case of submerged laser peening, it is believed that shock wave induced by laser abrasion is used to surface improvement. However, it was reported that bubble which was named as “laser cavitation” was developed after laser abrasion and impact at bubble collapse was larger than that of laser abrasion. In the present paper, in order to demonstrate surface improvement by submerged laser peening enhancing bubble collapse impact, stainless steel specimen made of JIS SUS316L was treated by the submerged laser peening and fatigue strength was investigated by using a displacement controlled plate bending fatigue test. The wave length of the used Nd:YAG laser with Q switch was 1,064 nm and the pulse energy was about 0.35 J. The impact induced by the laser abrasion and laser cavitation was measured by a special made PVDF sensor and a submerged shock wave sensor. In order to optimize pulse density at the submerged laser peening, the fatigue life was investigated at constant bending stress changing with the pulse density. It was revealed that the impact measured by the PVDF sensor induced by the laser cavitation was 1.4 times larger than that of laser abrasion and the fatigue strength of the specimen treated by the submerged laser peening was about 8 % larger than that of non-peened specimen.