This work examines the geometrical and thermodynamical properties of mechanical behavior of metals and many polymeric and paste-like materials which are indispensable for developing a rational theory of viscoplasticity. The book is intended for researchers as well as Ph.D. students in the fields of material science and continuum mechanics. Anyone involved in the design of large scale industrial parts will also find this book highly useful. The concepts and results illustrated in this work are readily applicable to the rapidly developing field of biomechanics.