KINEMATICS AND KINETICS OF CRYSTAL PLASTICITY
Crystal plasticity is overwhelmingly a consequence of the self similar translations of dislocations, which is viewed as a limiting form of more general shear transformations that also include twinning and martensitic transformations. Unlike elastic deformation, which can be homogeneous down to the atomic scale, plastic deformation involving dislocation translations or other shear transformations are locally discrete and inhomogeneous. Plasticity can be viewed as homogeneous only when the discrete processes are homogenized over a representative volume element (RVE), large enough to represent quasi-smooth behavior. Thus, for the purpose of viewing plasticity as a continuum field theory, its applicability is limited to volume elements no smaller than the RVE over which processes have been homogenized. In this chapter, the essential kinematics of inelastic deformation is introduced broadly. This is followed by the development of dislocation line properties that are associated with plastic strain production and the expenditure of plastic work in crystal plasticity, including concepts of dislocation line tension, dislocation mass, forms of interaction of dislocations with applied stresses, with each other, with free surfaces, and inhomogeneities. The principles of thermally activated deformation processes are introduced and then applied to dislocation glide and overcoming of local obstacles by thermal assistance. The detailed developments of dislocation properties emphasize face centered cubic crystals, including a full complement of partial dislocation and their dislocation.
Keywords: shear transformations, dislocation glide and climb, free surfaces, dislocation line tension, dislocation mass, dislocation multiplication, thermally activated deformation, close packed crystals, FCC and HCP structures, Thompson tetrahedron
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