A comparative study of stress update algorithms for rate-independent and rate-dependent crystal plasticity

The paper presents a comparative discussion of stress update algorithms for single-crystal plasticity at small strains. The key result is a new unifie d fully implicit multisurface-type return algorithm for both the rate-indep endent and the rate-dependent setting, endowed with three alternative appro aches to the regularization of possible redundant slip activities. The fund amental problem of the rate-independent theory is the possible ill conditio n due to linear-dependent active slip systems. We discuss three possible al gorithmic approaches to deal with this problem. This includes the use of al ternative generalized inverses of the Jacobian of the currently active yiel d criterion functions as well as a new diagonal shift regularization techni que, motivated by a limit of the rate-dependent theory. Analytical investig ations and numerical experiments show that all three approaches result in s imilar physically acceptable predictions of the active slip of rate-indepen dent single-crystal plasticity, while the new proposed diagonal shift metho d is the most simple and efficient concept. Copyright (C) 2001 John Wiley & Sons, Ltd.