A numerical description of short fatigue cracks interacting with grain boundaries

Abstract Short fatigue cracks typically propagate in stage I in which interaction with grain boundaries results in a fluctuating crack growth rate. Although there are established models, like the Bilby–Cotrell–Swinden theory and the Weertman model for crack growth and the model of Tanaka and Navarro and De Los Rios for their interaction with grain boundaries, a quantitative description of fatigue resistance is lacking. A unique technique combining focused ion beam based artificial crack initiation and three-dimensional tomography was used to separate the different influences of crack parameters and grain boundary parameters. The mechanisms which determine the strength of a grain boundary against crack propagation were thereby identified. Finally, it is shown how the models mentioned above can be easily used to calculate crack propagation through a grain boundary from single-crystal data and the orientation of the neighbouring grains only. This gives a promising perspective to improve fatigue life prediction and fatigue resistance of cyclically loaded materials.