Analysis of crack propagation using ΔK and Kmax

In this investigation a general relationship between fatigue crack growth rate, da/dN, and a two-parameter ΔK and Kmax driving force is derived using fundamental fatigue (ε-N curve) properties. A power-law relationship between ΔK and Kmax is obtained by relating the crack growth rate to the fatigue life of the 'process zone'. Theoretically, there are four different regions on a log-log plot depending on the particular combinations of ΔK and Kmax. The actual analysis of experimental data indicates only two different regions namely, ΔK and Kmax dominated, corresponding to high and low load ratios, respectively. A new way of representing the da/dN data in terms of ΔK and Kmax by means of the crack propagation (CP) table is proposed. Finally, the application of the CP table for predicting crack growth rate under constant amplitude loading is explained and discussed.