A crack closure model of fatigue crack growth in plates of finite thickness under small-scale yielding conditions

Abstract

Crack growth rates are significantly affected by the thickness of the specimen when all other parameters are kept constant. A quantitative estimation of the thickness effect is thus necessary to make predictions of crack growth rates more accurate and reliable. For this purpose a theoretical model was developed based on the strip-yield assumption and first-order plate theory. No empirical or fitting parameters were used in this work unlike some previous studies. The theoretical values obtained for the normalised load ratio parameter, U, were employed to describe experimental data, obtained under small-scale yielding conditions, at various load ratios and plate thicknesses. Such a representation considerably narrowed the scatter in the crack growth rates versus the effective stress intensity factor range, ΔKeff, demonstrating the potential of the theoretical model.