Introduction

To formulate interactions between defects and stress it is useful to classify the various types of defect and stress that will be of concern to us. Of the defects considered in this book, inclusions, point defects, dislocations, and various interfaces containing discrete intrinsic dislocations are sources of stress, and they therefore interact elastically with imposed stress, which may be internal stress due, for example, to the presence of other defects, or applied stress, due to forces applied to the body.

On the other hand, when a defect source of stress lies in a finite region bounded by interfaces, an image stress is generated, as described in Section 3.8, which then interacts with the defect. Thus, the interface acts, in a sense, as the source of a stress that interacts with the defect. In addition, an inhomogeneity, which by itself is not a source of stress, causes a perturbation of an imposed stress field, which, in turn, interacts with the imposed stress. An inhomogeneity may therefore be regarded as the indirect source of a stress that interacts with an imposed stress.