POLYCRYSTAL CONSTRAINT AND GRAIN SUBDIVISION

Typically, intergranular constraint relations of various sorts are int roduced to improve the accuracy of prediction of texture evolution and macroscale stress-strain behavior of metallic polycrystals within the context of simple polycrystal averaging schemes. This paper examines the capability of a 3-D polycrystal plasticity theory (Kocks, U.F., Ka llend, J.S., Wank, H.-R., Rollett, A.D. and Wright, S.I. (1994), popLA , Preferred Orientation Package-Los Alamos. LANL LA-CC-89-18), based o n the Taylor assumption of uniform deformation among grains, to predic t texture evolution and stress-strain behavior for complex finite defo rmation loading paths of OFHC Cu. Compression, shear and sequences of deformation path are considered. It is shown that the evolution of tex ture is too rapid and that the intensity of peaks is more pronounced t han for experimentally measured pole figures. Comparisons of both stre ss-strain behavior and texture evolution are made with experiments, wi th and without the inclusion of latent hardening effects. It is argued that grain subdivision processes accommodate intergranular kinematica l constraints, leading to the notion of a generalized Taylor constrain t that considers the distribution of subgrain orientations. The subdiv ision process is assumed to follow the experimentally observed refinem ent of low energy dislocation structures associated with geometrically necessary dislocations. A modification of the kinematical structure o f crystal plasticity is proposed based on generation of geometrically necessary dislocations that accommodate a fraction of the plastic stre tch and rotation at the scale of a grain. (C) 1998 Elsevier Science Lt d. All rights reserved.