TANGENT CONSTITUTIVE MATRICES FOR INELASTIC FINITE-ELEMENT ANALYSIS

A general formulation is presented for the tangent constitutive matrices of rate‐independent material models which assume that the strain increment consists of two components. One component is related to the stress increment through a known constitutive matrix, while the other component results from deformation mechanisms not reflected in the constitutive matrix. The procedure to modify the known matrix for these additional strains is specified. The formulation is a generalization of the well‐known procedure used in plasticity to modify the elastic constitutive matrix for plastic deformation. Application to both the classical and endochronic theories of plasticity and to a smeared crack theory is illustrated. Copyright © 1990 John Wiley & Sons, Ltd