A three-invariant cap plasticity with isotropic-kinematic hardening rule for powder materials: Model assessment and parameter calibration

The constitutive modeling of powder is clearly a keystone of successful quantitative solution possibilities. Without a reasonable constitutive model, which can reproduce complicated powder behavior under loading conditions, the computations are worthless. In this paper, a three-invariant cap plasticity model with isotropic-kinematic hardening rule is presented for powder materials. A generalized single-cap plasticity is developed which can be compared with some common double-surface plasticity models proposed for powders in literature. The hardening rule is defined based on the isotropic and kinematic material functions. The constitutive elasto-plastic matrix and its components are derived by using the definition of yield surface, material functions and nonlinear elastic behavior, as function of hardening parameters. The procedure for determination of material parameters is described. Finally, the applicability of the proposed model is demonstrated in numerical simulation of triaxial and confining pressure tests. (C) 2007 Elsevier B.V. All rights reserved.