Adjusted compliance ratio (ACR) is an experimental methodology (originally developed by Keith Donald) for mitigating the effects of remote closure on crack growth rate measurements which relies on the compliance method for measuring crack growth rates for estimating ∆Keff. It differs from the traditional methodology because it accounts for crack-tip strain below the opening load.
ACR is permitted in ASTM E647-15e Appendix X4. It has been fully incorporated into the FTA FCGR software and is available as an optional add-on feature. This is especially useful for materials exhibiting high levels of residual stress. ACR-corrected data in combination with second order Kmax effects have also been used to successfully provide a unique material property master curve.
