SIMULATIONS OF TEXTURE DEVELOPMENT IN CALCITE - COMPARISON OF POLYCRYSTAL PLASTICITY THEORIES

Deformation modelling based on polycrystal plasticity theory has been applied to several rocks. Recently it has been demonstrated that rate sensitivity and heterogeneous deformation can have a significant influence on the activation of slip systems and corresponding texture development. In this study previous predictions for pure shear deformation of calcite with the rigid-plastic fully constrained Taylor theory are compared with those from a visco-plastic Taylor theory, a relaxed Taylor theory and a visco-plastic self-consistent theory. In the case of calcite, texture simulations for all models are similar and conclusions based on earlier data remain valid. There are some quantitative differences and these will be discussed. A new procedure for dealing with mechanical twinning is proposed; it requires the volume fraction of twin reoriented grains to match the twinning fraction given by the twinning shears.