Mechanics Today, Volume 6 is part of a series of book that compiles various materials about mechanical engineering. The coverage of the title includes theoretical and applied mechanics and applied mathematics. The text first details the general framework within which macroscopic overall response parameters of continuous bodies. Next, the selection covers the integration of theory of singularities and the calculus of variations. The third chapter deals with the elastic-plastic response of a structure to cyclic loading. The title also talks about the mixed boundary-value problems in mechanics. The book will be of great use to both student and professional mechanical engineers.