A correlation between unified constraint parameter and J-R curves of different metallic materials

To enhance the safety of service and the economic efficiency of operation and maintenance of cracked structures in structural integrity assessment, it is essential to investigate and establish the general correlation of constraint-dependent J-R curves for different metallic materials. This research makes use of a large number of J-R curves data of different metallic materials. These data are predominantly measured or simulated from SEN(B) specimens with different geometries and sizes (representing various constraint levels). Additionally, the research utilizes the load-independent unified constraint parameter A_d* data calculated for each specimen through the finite element method. Based on these data, a general correlation equation of constraint-dependent J-R curves for different metallic materials has been established. This general correlation equation can predict constraint-dependent J-R curves for components or structures with varying levels of constraint and different metallic materials, and its predictive capability and accuracy have been validated using experimental and simulated J-R curves data of different homogeneous materials and welded joint materials. This general correlation equation can provide a simple and convenient approach to predicting and estimating constraint-dependent J-R curves, significantly lowering both experimental and computational costs, and has a broad application range for metallic materials, loading modes, geometries and crack sizes.