A closure model to crack growth under large-scale yielding and through residual stress fields

This paper presents a closure model for predicting the growth behavior of short cracks in the presence of large-scale yielding and residual compressive stresses, representative of structures that have been shot-peened. The plasticity-induced crack closure model developed by Newman is first extended by using the cyclic crack-tip opening displacement as the correlating parameter for fatigue crack growth rates. This new approach also enables a better characterization of the effect of large-scale yielding on short crack growth. The effect of residual stress on crack closure is then analyzed by adding to the loading spectrum an equivalent stress, which varies with the applied load level and the crack size. It is shown that predictions of the extended closure model are within a factor of two of the experimental results of etched specimens tested under spectrum loading, highlighting the capability of the predictive model along with some important issues for future research in this area.