Safety of material is the top priority in the design of any product. Proper understanding of mechanics of the deformable bodies is required to provide safety to any material. This book deals with the basic principles of strength of materials with respect to deformable bodies. Strength of materials or elements of mechanics of materials is an important subject for civil, mechanical, industrial production, aeronautical and automobile engineering students who are required to acquire wide knowledge of basic mechanism involved in mechanics. It is a vast field and is largely taught at the undergraduate level. The topics are covered with relevant conceptual explanation and with illustrative examples in nine modules. Several complicated topics like failure theories and compound stress are covered with explanation. Numerical examples have been solved covering all complexities. At the end of each chapter, a sufficient number of problems are provided as exercise.