Stochastic crack growth analysis methodologies for metallic structures

Abstract

Stochastic crack growth analysis methodologies are proposed and evaluated for predicting the statistical crack growth damage accumulation in metallic structures. These new methodologies have several practical applications for metallic airframes, including: (1) ensuring U.S. Air Force damage tolerance and/or durability design requirements, (2) reliability centered maintenance, and (3) structural reliability based designs. They can easily be implemented using deterministic crack growth analysis results and an estimate of the crack growth life dispersion. Two different stochastic crack growth approaches are proposed (i.e. “general” and “analytical”). The “general” approach uses a numerically defined deterministic (median) crack growth curve directly. Whereas, the “analytical” approach approximates the median crack growth curve with one or more compatible crack growth segments. Analytical predictions for both approaches are correlated with experimental test results. Good correlations are obtained for a wide range of crack sizes. These proposed approaches represent a new contribution to the state-of-the-art in the applications of statistical crack growth damage predictions for metallic structures in service.