Reliability Improvement for Fatigue Characteristics of STS316L Steel Using Surface Crack Non-damaging Technology

Cracks degrade the performance and reliability of steel structures; hence, researchers are extensively investigating solutions to the crack problem to ensure safety and easy maintenance of structures. A new technique has been developed in this work to render surface cracks harmless, which also reduces the fatigue limit by the influences of compressive residual stress caused by peening; this technique is referred to as surface crack non-damaging technology. This study aims to contribute toward reliability improvement of the of Ni 12% STS316 steel via the surface crack non-damaging technology. The crack depth (a(hlm)) that could be rendered harmless by ultrasonic peening (UP) was largely dependent on the compressive residual stress. Further, am m increased as the crack aspect ratio (As) and threshold stress intensity factor (Delta K-th(l)) increase. At large residual stress, the crack did not propagate and were rendered harmless. The relationship between a(hlm), a(NDI) (the crack depth that can detected by nondestructive inspection), and a(crN) (the maximum crack depth in the assumed safety factor) were compared.