The title of this book is derived from a graduate course in which Professor Egon Orowan presented to M.I.T. students a clear and simple picture of the basic concepts in crystal plasticity and the mechanics of fracture of materials. Since the publication of his pioneering papers on dislocations and atomic mechanisms of fracture in the early 1930's, Professor Orowan has been one of the principal contributors to the field of physics of plasticity and strength. During the past 10 to 15 years, the perfection of many direct experimental methods has caused a great increase of activity in the...