Constitutive models for cohesive particulate materials

This paper reviews several constitutive models for the load response of bulk solids. Constitutive models based on microscopic concepts and continuum principles are presented. The review demonstrates the need for a generalized constitutive model that can predict the stress-strain behaviour of cohesive powders, since none have yet been found. However, two continuum models have been identified as having sufficient versatility to be chosen as candidate models for application to cohesive food and agricultural powders. One model is an elasto-viscoplastic model based on the critical-state theory, and includes seven material parameters in the constitutive equations. The second model uses the endochronic theory to characterize stress-strain response, and requires 15 parameters in the formulation. Both models can be used for isotropic and anisotropic loading conditions, as well as monotonic and cyclic loading.