A crystal plasticity based approach for the modelling of high cycle fatigue damage in metallic materials

In this paper, a polycrystalline model is proposed to describe the fatigue behaviour of metallic materials in the high cycle fatigue regime. The model is based on a multiscale approach, which allows the connection of local deformation and damage mechanisms to macroscopic behaviour. To consider the anisotropy of plastic properties, the constitutive model is developed at the grain scale within a crystal plasticity framework. A phenomenological approach, which requires the introduction of a damage variable for each slip system, is used to account for the anisotropic nature of damage. The constitutive model is then integrated within a self-consistent formulation to consider the polycrystalline nature of metallic materials. Finally, the proposed model is used to describe the high cycle fatigue behaviour of a medium carbon steel (0.35% C). With a proper adjustment of material parameters, the model is capable of correctly reproducing fatigue test results, even for complex loading conditions (multiaxial, non-proportional). According to the model, damage is found to be highly localized in some specific grains. Also, while fatigue damage results in a progressive decrease in elastic stiffness at the crystal scale, the elastic properties are not significantly affected at the macroscopic scale. The model is used to study the correlation between energy dissipation and fatigue damage. According to the numerical results, no evident correlation between fatigue damage and energy dissipation is observed.