Stability of flow processes for dissipative solids with internal imperfections

The onset of the instability of flow process for dissipative bodies with internal imperfections was studied. Formulation of a quasi-static, isothermal flow process for a bounded body is given. Criteria of localization of plastic deformations are considered. The postcritical behavior for dissipative solids is described by a very precise constitutive model and important cooperative effects such as internal imperfections, strain rate sensitivity, etc., are taken into consideration. The constitutive modelling is developed within the framework of two material structures, namely the internal state variable and rate type material structures. The influence of internal imperfections and transport phenomena governing the evolution of imperfections in time and its distributions in a body during the flow process are described. Physical and experimental motivations for these effects are given and theoretical proposition describing the nucleation, growth and diffusion of voids is presented.