Dislocations and disclinations: continuously distributed defects in elasto-plastic crystalline materials

摘要

The paper deals with elasto-plastic models for crystalline materials with defects, dislocations coupled with disclinations. The behaviour of the material is described with respect to an anholonomic configuration, endowed with a non-Riemannian geometric structure. The geometry of the material structure is generated by the plastic distortion, which is an incompatible second-order tensor, and by the so-called plastic connection which is metric compatible, with respect to the metric tensor associated with the plastic distortion. The free energy function is dependent on the second-order elastic deformation and on the state of defects. The tensorial measure of the defects is considered to be the Cartan torsion of the plastic connection and the disclination tensor. When we restrict to small elastic and plastic distortions, the measures of the incompatibility as well as the dislocation densities reduced to the classical ones in the linear elasticity. The constitutive equations for macroforces and the evolution equations for the plastic distortion and disclination tensor are provided to be compatible with the free energy imbalance principle.