Initial Development of a Fatigue-Crack-Retardation Model

A fatigue-crack-propagation model is developed by reducing crack-tip plasticity to a single pair of enlarged dislocations, termed superdislocations, whose response is equivalent to that of the aggregate plastic zone. The crack-tip damage or deformation and accompanying incremental crack advance resulting from each loading cycle are accumulated in a single super-superdislocation pair for residual interaction on the next loading cycle. Key features of this development are that the required material parameters are limited to the shear modulus, Poisson's ratio, and tensile-yield strength, and that crack-surface closure is accommodated. A significant simulation of the fatigue-crack-propagation process along with a promising correlation with experimental results are achieved. (Author)