Volume 1, Issue 10 (November 2004)
A Framework for a Standardization Effort for Fatigue Crack Growth Testing Under Variable Amplitude Spectrum Loading
Fatigue crack growth testing under variable amplitude loading conditions is currently not standardized. Without standardization, the methods and techniques applied by different laboratories vary, and as such, lab-based bias can occur readily. The goal of this paper is to discuss in detail the experience developed and lessons learned during years of spectrum crack growth testing. Issues concerned with specimen geometry, crack geometry, precracking methodology, crack length measurement, spectrum content, load magnitude control, and interpretation of results are addressed herein. Although the ASTM Standard Test Method for Measurement of Fatigue Crack Growth Rates, E 647, provides guidance that is useful to this test, the specialized nature of spectrum testing does provide its own unique set of issues different from da/dN versus ΔK testing.