Complete Fatigue Crack Growth Rate Curves for Aluminum Alloy 2124-T851 Including Typical Crack Growth Models

摘要

Complete fatigue crack growth rate curves for aluminum alloy 2124-T851 were developed for two stress ratios: R = +0.1 and +0.5. The data sets obtained range from the threshold stress intensity range, KTH, to the value of stress intensity required for unstable crack propagation. Crack length measurements were obtained using both the traditional visual method and a compliance method developed for the elongated compact specimen. Humidity and temperature were controlled and the effect of specimen thickness was examined. For a constant stress intensity range the effect of an increase in R-ratio was to increase the growth rate. The crack growth rate data obtained via the visual and compliance methods are in good agreement over the range investigated. No thickness effects was observed. A variety of model equations were statistically fitted to the data. These models include the Paris, Walker, and Forman equations along with a form of the hyperbolic equation. These equations were examined for accuracy with advantages and shortcomings noted. (Author)