Speaker
Description
Crystal plasticity theory offers a powerful framework for analyzing plasticity at different scales while incorporating crystallographic information into the constitutive model. Unfortunately, classic rate-independent crystal plasticity models face long-standing problems regarding the determination of active slip systems and the computation of non-unique solutions. A very popular and already well-established algorithm is based on an augmented Lagrangian formulation. Due to its fixed-point update, the algorithm diminishes the effect of ill-posed crystal plasticity and therefore poses a robust algorithmic framework. Unfortunately, this scheme also makes the algorithm slow due to necessary inner and outer iterations. Therefore, measurements to improve the efficiency are discussed first. Subsequently and based thereon, a completely novel algorithm is developed which combines the benefits of an augmented Lagrangian formulation with those of nonlinear complementarity problems (NCP). The novel algorithm also does not pose any ill-conditioning and is significantly more robust and efficient than the original augmented Lagrangian formulation. Several numerical examples including statistical evaluations of various random crystal orientations as well as RVE simulations of a polycrystal demonstrate the properties and limits of the proposed algorithm.
