9312858 Rosakis This work studies the micromechanics of dynamic twin growth and the evolution of phase boundaries in crystalline alloys of engineering importance. The study of twinning is a prerequisite to the understanding of martensitic transformations and of the shape- memory effect. The general method of approach is base don the modern theory of nonlinear elastodynamics of materials that change phase. An important ingredient will be the choice of a constitutive law, namely a strain energy function which has many local minima (potential wells) as a function of strain and exhibits and appropriate type of anisotropy. A class of dynamic problems involving rapid propagation of twinned zones into untwinned crystals will be formulated and analyzed. ***
