AN ANISOTROPIC DAMAGE MODEL FOR METALS BASED ON IRREVERSIBLE THERMODYNAMICS FRAMEWORK

In this article, a model of anisotropic damage coupled to plasticity based on
thermodynamics framework is proposed. This model is introduced to describe the plastic and
damage behavior of metals adequately. According to the elastic energy equivalence hypothesis
between the undamaged material and the damaged material, the constitutive equations for the
material in damaged configuration are written. The damaged material is modeled using the
constitutive laws of the undamaged material in which the stresses in undamaged configuration are
mapped by the stresses in damaged configuration. The damage is proposed through a damage
mechanics framework, and the material degradation is determined by utilizing an anisotropic
damage measure. In developing constitutive model, a plastic yield surface is used to demonstrate
the onset of plasticity, and a damage surface is used to demonstrate the onset of damage.
The plastic relationships have been written in undamaged configuration, and by using
relationships between damaged and undamaged configurations, plastic equations are extended to
damaged configuration.
Numerical simulations of the elastoplastic deformation behavior of hydrostatic stress
sensitive metals demonstrate the efficiency of the formulation, and also show the physical effects
of parameters of the model. In order to achieve an equilibrated global solution, a nonlinear finite
element program that employs a Newton Raphson iteration procedure is applied. Finally, the
numerical results of some examples are validated with the existing experimental measurements.