THE PLASTIC SPIN IN VISCOPLASTICITY

The importance of the role of plastic spin in the rate-dependent response of materials at large deformations is the main objective of this work. After a brief presentation of a general constitutive framework for viscoplasticity at large strains, an isotropic/kinematic hardening and an orthotropic viscoplastic model are used to analyze the stress-strain response under simple shear and biaxial loading at different rates. A clear understanding of the role of plastic spin is achieved by obtaining closed-form analytical expressions for different stress values, in which the plastic spin constitutive parameters interrelate with the strain rate and other more conventional model constants. Such analytical expressions allow for a direct evaluation of the capabilities of the models to account for large deformations and rate dependence as exhibited by available experimental data, and provide guidance towards the proper choice of constitutive parameters. © 1990.