Evaluation of the Adjusted Compliance Ratio Technique for Measuring Crack Closure in Ti-6A1-4V

Résumé du livre

Standard fatigue crack growth rate tests within the upper threshold and Paris Law regions were conducted on specimens from three large, standard-grade Ti-6Al-4V forgings in order to evaluate the adjusted compliance ratio (ACR) method for closure correction. Constant R-ratio tests were conducted to generate data containing crack-tip closure, and constant Kmax tests were performed to produce high R ratio, and hence closure-free, data in the threshold and upper threshold regimes. Direct comparisons are made of the closure corrected data generated using the current ASTM slope offset method and the ACR method. While it is clear that the ACR technique is easier to implement and will always lead to less closure correction than the slope offset technique, it is not clear which is more accurate. It appears that the slope offset method may be overcorrecting for closure effects and the ACR method may be undercorrecting.