Isolation of contributions of residual stress and weld microstructure to fatigue crack growth rates in welds

Weld residual stresses and microstructural changes show coupled effects on fatigue crack growth rates resulting in more difficulties and complexity in crack growth life analysis for weld joints. Uncoupling these effects is a desirable option for understanding the influence of each factor and establishing more accurate crack growth prediction methods. A method for isolating the contributions of residual stress and weld microstructure change to fatigue crack growth rates in welds is presented in this paper. The proposed method is based on the superposition rule in fracture mechanics. Example of fusion weld specimens of different configurations and subjected to different loading conditions are presented to demonstrate the procedure of the method. Factors that will influence the solution, such as the applied and residual stress intensity factors, effective stress intensity factor ratio, choice of crack growth laws etc. are assessed and discussed in details.