Homogenized constitutive and fatigue nucleation models from crystal plasticity FE simulations of Ti alloys, Part 1: Macroscopic anisotropic yield function

Deformation and fatigue failure behavior of polycrystalline titanium alloys have strong dependence on the local microstructural characteristics. Reliable analysis of mechanical response and fatigue life in structures is contingent upon accurate description of material behavior using continuum-level constitutive models, with roots in the underlying microstructure. This two part paper is aimed at developing continuum models of plastic deformation and fatigue crack nucleation in polycrystalline Ti alloys from detailed analysis of underlying polycrystalline microstructures. In the first of this two-part paper, a homogenized, anisotropic plasticity constitutive (HAPC) model is developed from crystal plasticity finite element simulation results of microstructural representative volume elements. This model is able to capture important deformation characteristics of Ti-based alloys, which are pressure insensitivity, anisotropy and tension–compression asymmetry. The advantage of this model is that it avoids having to perform computationally expensive micromechanical analysis at each point in macroscopic simulations. An extension of this model is also introduced to account for the rate dependency observed in mechanical behavior of Ti alloys. In the second part of this two-part paper, a macroscopic, probabilistic fatigue crack nucleation model is developed using the HAPC model.