An overview of the constitutive behavior of crystalline solids

Abstract

An overview of the general principles involved in the mechanics of crystalline solids is presented. The emphasis is on the inelastic behavior, and particularly on microcracking, in brittle crystalline solids. A phenomenological theory of microcracking which is based upon application of the internal variable theory of continuum thermodynamics (the so-called continuous damage theory) is suggested to be inadequate for a clear description of the phenomena that occur on the microscale. Also, it is emphasized that the phenomenological theories of plasticity are inapplicable at the very early stages of microplasticity prior to microfracture, when the inelastic deformations are highly heterogeneous on the scale of a grain size, and at the very late stages of plasticity, when either shear band localization or necking occurs as a result of the non-normality of the constitutive structure. It is, therefore, suggested that there is need for development of micromechanical constitutive theories which will embody the nature and the extent of microstructural changes that occur during inelastic deformation.