Effect of residual stress redistribution on fatigue crack growth pertinent to crack closure and applied load

Clarifying residual stress (RS) redistribution and its effect on fatigue crack growth (FCG) is essential to evaluate the fatigue life of a welded joint. In this study, initial RS distribution along FCG path is calculated based on FCG measurements of as-welded and heated-treated specimens. Subsequently, RS redistribution with crack growth is studied by two groups of specimens with gradually decreased distances between notch tip and weld centerline, and its influence on FCG is linked to crack closure and applied load. The results show that RS redistribution mainly depends on the distance from crack tip to weld centerline, and RS at a crack tip is always compressive during fatigue cycling. In addition, the length of contacted crack wake gradually increases at the beginning of FCG (crack closure effect), which decreases FCG rate together with compressive RS at a crack tip.