SIMULATION OF THE BEHAVIOR OF FCC POLYCRYSTALS DURING REVERSED TORSION

Taylor-type polycrystal plasticity models with various single slip har dening laws are evaluated by studying the large strain behaviour of FC C polycrystals during reversed torsion. The hardening laws considered include the model of Asaro and Needleman (''Texture Development and St rain Hardening in Rate Dependent Polycrystals,'' Acta Metall. (1985), 34, 1553) as well as a power-law and an exponential Version of that, a nd a more recent model by Bassani and Wu (''Latent Hardening in Single Crystals II. Analytical Characterization and Predictions,'' Proc. R. Sec. Lend. (1991), A435, 21). The material parameters for the various hardening laws are fitted to experimental compression data for copper and then used to predict reversed large strain torsion of tubes. Diffe rences under ''free-end'' (axially unconstrained) or ''fixed-end'' (ax ially constrained) conditions between predictions and experimental obs ervations are discussed in detail. In addition to the torque response, the Swift effects upon twist reversal are studied. Copyright (C) 1997 Eisevier Science Ltd.