Simple Scaling as a Tool to Help Assess the Closure-Free da/dN Versus ΔKeff Curve in a Range of Materials

Abstract

Recent studies have proposed a simple formula, which is based on Elber’s original approach to account for R-ratio effects, for determining the crack closure-free ΔKeff versus da/dN curve from the measured R-ratio-dependent ΔK versus da/dN curves. This approach, which is termed “Simple Scaling,” has been shown to collapse the various R-ratio-dependent curves onto a single curve. Indeed, this approach has been verified for a number of tests on metals, polymers, and a medium-entropy alloy. However, it has not yet been used to help assess/determine the closure-free ΔKeff versus da/dN curve. The current paper addresses this shortcoming and illustrates how to use this methodology to assess the ΔKeff versus da/dN curves given in the open literature for tests on a number of steels, aluminum alloys, STOA Ti-6Al-4V, a magnesium alloy, and Rene 95. As such, it would appear to be a useful tool for assessing fatigue crack growth.