It has been observed that the loss of crack tip constraint leads to enhanced resistance to both cleavage and ductile tearing. Recent developments on constraint-based fracture mechanics have enabled the practical assessment of defective components including the constraint effect. However, how to quantify the effect of crack tip constraint on the fatigue crack propagation rate is still an open issue. It is common practice to use the Paris crack propagation law, which is based on the stress intensity factor alone. In this paper, the effect of crack tip constraint on the fatigue crack propagation of small cracks at T-plate welded joints is investigated. A fatigue crack propagation rate model is developed incorporating both low and high constraint conditions. It is shown that the effect of constraint on crack propagation rate is significant when the crack is small (within the stress concentration of the weld joints). This effect can be accounted for by using the proposed fatigue crack propagation rate model.
Fatigue Crack Propagation Rate of High Strength Steel's Welded Joints
