Statistics of Crack Growth in Engine Materials. Volume 1. Constant Amplitude Fatigue Crack Growth at Elevated Temperatures

摘要

Classically crack propagation analyses for engine components employed in residual life predictions are deterministically based. They typically account for materials scatter by the incorporation of a safety factor. A statistical treatment of materials scatter is necessary to permit a maximum utilization of component life. Two fracture mechanics-based statistical models for the fatigue crack growth damage accumulation in engine materials are proposed and investigated. These statistical models are based on the synergistic fracture mechanics models, i.e., hyperbolic sine crack growth rate function, developed by Pratt and Whitney. Test results of IN-100, a superalloy used in the F-100 engine, at various elevated temperatures, loading frequencies, stress ratios, etc., have been compiled and analyzed statistically. The statistical distributions of (1) the crack growth rate; (2) the propagation life to reach any given crack size; and (3) the crack size at any service life, have been derived. It is demonstrated that the correlation between the test results and two statistical models is very good. (Author)