CONTINUUM SLIP VISCOPLASTICITY WITH THE HAASEN CONSTITUTIVE MODEL - APPLICATION TO CDTE SINGLE-CRYSTAL INELASTICITY

Small strain constitutive equations are developed for the thermomechan ical behavior of semiconductor single crystals, including dislocation density as an evolving parameter. The model of Haasen, Alexander and c oworkers is modified (extended) to include evolution of coefficients i n the definition of internal stress. These account for an evolving dis location substructure. The resulting model is applied in a continuum s lip framework to allow multiple slip orientations. Slip system interac tion rules are adapted to include slip system interaction for multiple slip conditions and to suppress secondary slip and dislocation densit y generation for single slip orientations. The approach is discussed r elative to other models for viscoplasticity of single crystals and is examined in the context of thermodynamics with internal state variable s. The framework is used to correlate experimental data from compressi on tests of single crystals of the compound semiconductor CdTe from ro om temperature to near the melting point. Sensitivity of the model to uncertainties such as initial dislocation density is explored.