Kyounghee Gu1,Chang-Seok Oh2,Cheol-Su Kim1,Seok-Hee Kang1,Jae-Eun Paeng1,Ki-Woo Nam1
Pukyong National University1,POSCO2
Kyounghee Gu1,Chang-Seok Oh2,Cheol-Su Kim1,Seok-Hee Kang1,Jae-Eun Paeng1,Ki-Woo Nam1
Pukyong National University1,POSCO2
Recently, surface crack nondamaging technology has been developed to render harmless surface cracks that can reduce the fatigue limit of metals by 20–60%. This is due to the effects of compressive residual stress induced by shot peening. This study evaluated the characteristics depending on steel with the different carbon content using surface crack nondamaging technology. First, the fatigue limit according to the size of microcracks was evaluated. Next, Using the threshold stress intensity factor and the residual stress distribution by shot peening (<i>SP</i>), the <i>As</i> dependence of the harmless maximum crack depth and the <i>As</i> dependence of crack depth which lowers the fatigue limit of non-<i>SP</i> smooth materials by 25% or 50% were evaluated. The relationship between minimum detectable crack depth via nondestructive inspection (a<sub>NDI1</sub> and a<sub>NDI2</sub>)and harmless maximum crack depth (a<sub>hlm</sub>), assuming that nondestructive inspection could detect the crack with sufficient probability were discussed.