Probabilistic predicting the fatigue crack growth under variable amplitude loading

The probabilistic method presented in this paper facilitates a simplified description of fatigue crack growth under variable amplitude loading and the estimation of fatigue life. Fundamental to the description is a finite difference equation with the coefficients originated from the Paris formula which models the dynamics of crack growth. The characteristic features of crack growth under overload–underload cycles existed in an exploitive loading were modeled by using the modified Willenborg retardation model. The presented probabilistic method has a good confirmation by experimental research of crack behavior and fatigue life estimation for an aeronautical aluminum alloy sheet 2024-T3 subjected to variable amplitude load program. This method needs an extension over the crack initiation period.