Load Interaction Effects on FCG: Master Curve Approach

The majority of fatigue crack growth (FCG) data associated with load interaction effects have been interpreted in terms of plasticity effects at the crack wake. This paper presents a new approach by which the FCG behavior for different R-ratios can be predicted using the master curve. In this approach, the stress intensity factor (SIF) range, ΔK, is normalized in terms of ΔK at R=0. The corresponding mean value of SIF, K_m, is normalized by the SIF amplitude, K_a. A curve is plotted for this normalized SIF data, which collapses all the R-ratios into a master curve and therefore enables the prediction of other R-ratios. From the analyses of different materials taken from literature it is demonstrated that the master curve approach is very effective in predicting the R-ratio effects on fatigue crack growth behavior.