A physically-based formulation for texture evolution during dynamic recrystallization. A case study for ice

Dynamic recrystallization can have a strong impact on texture development during the deformation of polycrystalline materials at high temperature, in particular for those with strong viscoplastic anisotropy such as ice. Owing to this anisotropy, recrystallization is essential for ensuring strain compatibility. The development of recrystallization textures leads to significant mechanical softening, both in laboratory or natural conditions (glaciers, ice sheets). Accurately predicting ice texture evolution due to recrystallization during tertiary creep remains a challenge, yet is crucial to account adequately for texture-induced anisotropy in large-scale models of glacial ice flow. We propose a new formulation for texture evolution due to dynamic recrystallization. This formulation is physically-based on an orientation attractor which maximizes the Resolved Shear Stress (RSS) on the easiest slip system in the crystal (basal slip for ice). The attractor is implemented in an equation of evolution of the crystal orientation with deformation, which is coupled to an anisotropic viscoplastic law (Continuous Transverse Isotropic - CTI) that provides the mechanical response of the ice crystal. The set of equations, which is the core of the R³iCe open source model is solved using finite elements method with a semi implicit scheme coded using the Rheolef library. R³iCe is validated by comparison with laboratory creep data for ice polycrystals under simple shear, uniaxial compression and tension. It correctly reproduces the texture evolution and the mechanical softening observed during tertiary creep. R³iCe therefore allows predicting enhancement factors that may be implemented in large-scale flow models. Although the validation was performed for ice, the R³iCe implementation is generic and applies for any material adequately described using a CTI law.