An Elasto-plastic Damage Constitutive Theory Based on Pair Functional Potentials and Slip Mechanism

 The deformation work rate can be expressed by the time rate of pair functional potentials which describe the energy of mate-rials in terms of atomic bonds and atom embedding interactions. According to Cauchy-Born rule, the relations between the microscopic deformations of atomic bonds and electron gas and macroscopic deformation are established. Further, atomic bonds are grouped according to their directions, and atomic bonds in the same direction are simplified as a spring-bundle component. Atom embedding interactions in unit reference volume are simplified as a cubage component. Consequently, a material model composed of spring-bundle components and a cubage component is established. Since the essence of damage is the decrease and loss of atomic bonding forces, the damage effect can be reflected by the response functions of these two kinds of compo-nents. Formulating the mechanical responses of two kinds of components, the corresponding elasto-damage constitutive equa-tions are derived. Considering that slip is the main plastic deformation mechanism of polycrystalline metals, the slip systems of crystal are extended to polycrystalline, and the slip components are proposed to describe the plastic deformation. Based on the decomposition of deformation gradient and combining the plastic response with the elasto-damage one, the elasto-plastic dam-age constitutive equations are derived. As a result, a material model formulated with spring-bundle components, a cubage component and slip components is established. Different from phenomenological constitutive theories, the mechanical property of materials depends on the property of components rather than that directly obtained on the representative volume element. The effect of finite deformation is taken into account in this model. Parameter calibration procedure and the basic characteris-tics of this model are discussed.