Rodney Hill wrote his preface to The Mathematical Theory of Plasticity 41 years ago this month. As a reader of the present monograph likely knows, that classic work dealt with the macroscopic theory of metal plasticity and its applications as the subject stood at mid-century; and Hill only briefly (albeit superbly) discussed in his introductory chapter the physical background of the plastic properties of crystals and polycrystalline aggregates. The same year, however, saw publication of the English translation of an earlier (1935) classic specifically concerned with that background, Kristallplastizität by E. Schmid and W. Boas. Not entirely coincidentally, both Rodney Hill and this translation were associated with the Cavendish Laboratory, Cambridge, during the period immediately following World War II.

Each of these books when first published was in many respects a treatise on its respective subject, but there was no contemporary work which integrated these fields. Today, I doubt a comprehensive treatise could be written on all that has transpired both in the development of mathematical theory and in the experimental study of plastic behavior of crystalline materials during this century (or even since 1950). Accordingly, in planning and carrying out the writing of the present work, I decided to restrict its scope to those aspects of the broad subject of crystalline plasticity that have particularly interested me and that I have contributed to or at least seriously studied during the years since 1968.