ABSTRACT
In engineering systems contacts are often referred to as interfaces or joints between two materials. Such discontinuities may preexist or are induced in a deforming material system. Existence of discontinuities in a material body whose parts around and beyond the discontinuities may be continuous can lead the overall system to be discontinuous. Hence, the theories
based on continuum mechanics may not be applicable to characterize its response. As described in Chapter 2, an initially continuous body may experience internal microcracking during loading. Up to a certain extent of microcracks, the material may still be treated as continuous. However, the microcracks often coalesce and lead to zones of macrolevel fractures. As a result, the material may no longer be treated as a continuum. In fact, such finite-fracture discontinuities may represent interfaces or joints and need to be treated as such.
