Material Response IV: Elastic-Plastic and Elastic-Viscoplastic Solids

Abstract

Most solids exhibit elastic response only within a narrow range of stress or strain. Materials respond elastically to large compressive forces if they take the form of a uniform pressure, but their resistance to shear stress is limited. When ductile solids such as soft metals are subjected to shear stress, they can be severely deformed without fracturing, but they do not recover their original shape when the applied stress is removed. It is this response, plastic deformation, that is the subject of this chapter. Its investigation necessarily involves consideration of elastic response, and the theory is more complicated than that of elastic response alone. The observed phenomena are more varied than elastic responses and a range of theories is used to capture these phenomena. The simpler theories capture the observed phenomena in only the most rudimentary way. The more comprehensive theories capture a broader range of phenomena, and/or capture the more basic observations with a higher degree of fidelity, but this is accomplished only at a cost in complexity. The simpler theories are based upon the premise that the material response is independent of the rate of deformation, but rate effects are commonly observed and are captured by the more comprehensive theories.