Workability is often defined as the degree of deformation that can be achieved in a particular deformation processing operation without failure. Failure may be the basic material related phenomena of cracking or fracture, but it could also be any other undesirable condition, for example lack of die fill or poor surface finish. The major factors which influence the workability of a material are: (1) the external process variables of stress, temperature, strain, strain rate, frictional and heat transfer boundary conditions, and their evolution; and (2) the internal microstructural variables, for example porosity, crystallographic texture, deformation localization and their evolution culminating in ductile failure. While considerable attention has been paid to developing a capability for predicting defects associated with the growth of porosity in deformation processing operations, much remains to be done with regard to incorporating the evolution of other important microstructural features in macroscopic mathematical models. Specifically there is need for incorporating the effects due to crystallographic texture and deformation localization and failure. This project is to develop accurate anisotropic thermo- elastic-viscoplastic constitutive equations and computational procedures for modeling and simulation of inelastic deformations due to both crystallographic slip and twinning in face-centered cubic and hexagonal-closed packed alloys. The computational capability will be useful in simulating the development of anisotropy due to the evolution of crystallographic texture, and the development of material processing defects associated with localized shear bands at large deformations at both low and high homologous temperatures. The mathematical models should be useful in the design and analysis of a variety of cold and hot deformation processing operations. Such models will allow the faster and more accurate design of tools and procedures for forming metal parts.
