An Explanation for Near-Threshold Fatigue Crack Propagation Behavior in Welded Residual Stress Fields by Crack Closure Phenomenon

Abstract

Fatigue crack growth rates and threshold for crack propagation were determined for CCT and SEN specimens taken from the butt welded joints in 600 MPa grade steel. The crack opening stress has also been determined by using relation between the elastic compliance and loads. The compressive residual stresses resulted in the decrease of fatigue crack growth rates and the increase of threshold values. These behavior strongly depended on the stress ratio. While, the tensile residual stresses resulted in the increase of fatigue crack growth rates and the decrease of threshold values. These behavior scarcely depended on the stress ratio. The effects of welded residual stresses and stress ratio can be correlated by using the effective stress intensity range concept.