Improving reliability of high‐strength steel designed against fatigue limit using surface crack nondamaging technology by shot peening

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. To improve the reliability of high-strength steel equipment designed against fatigue limit using surface crack nondamaging technology, the following characteristics were determined: (1) the effects of surface crack aspect ratio on maximum harmless crack depth (a(hlm)) at high-strength steel for three residual stress distributions; (2) the relationship between the maximum allowable crack depth (a(crN)) and a(hlm) assuming the value of safety factor; (3) the relationship between minimum detectable crack depth via nondestructive inspection (a(NDI)) and a(hlm), assuming that nondestructive inspection could detect the crack with sufficient probability; and (4) the relationships between a(hlm), a(NDI), and a(crN).