Effect of Crack Closure‐Dependent Residual Stress on Fatigue Crack Growth of Welded Joints Pertinent to Applied Minimum Stress Intensity

ABSTRACT The effect of welding residual stress (RS) and applied stress on fatigue crack growth (FCG) rate is studied through comparison of FCG measurements from as‐welded and heat‐treated welded joint specimens with different initial RS and fatigue loading. Crack closure effect is quantified by redefining crack opening stress intensity factor ( K op )‐based on load‐COD (crack opening displacement) curve. The results show that RS effect on FCG is closely related to the minimum stress intensity factor ( K min ) and K op , and RS effect on FCG disappears when K min is greater than K op . When K op is greater than K min , the effective stress intensity factor range is calculated by subtracting K op from the maximum stress intensity factor ( K max ), and K op increases with K max during fatigue cycling.