ABSTRACT
This chapter analyses three characterized modes of plastic deformations by applying the laws of plasticity. The first deals with plastic instability in some simple applications to define limiting loads and strains associated with large plastic deformation, i.e., ductile failure. The second extends the application of plasticity laws to materials for which the flow stress depends on strain-rate, such as superplastic alloys. The third deals with the analysis of creep deformations of some simple structures. Plastic instability for a certain case of loading may be identified when the deformation changes its magnitude and configuration under the same load, e.g., when a state of uniform plastic deformation gives way to a nonuniform or, say, localized one. An annealed strip under uniaxial tensile load undergoes a state of unstable plastic deformation. As deformation continues at falling load, a neck with large profile radius is observed. Creep testing of engineering materials is mostly done under constant load and temperature in uniaxial testing machines.
