Introduction

In this chapter, the role of material inelasticity is considered, in the form of irreversible plastic flow, dependence of the material response on the rate of deformation, or microcracking. The study of issues in dynamic fracture mechanics concerned with these effects is at an early stage. Consequently, the sections are not integrated to any significant degree. Instead, each section is intended to give an impression of the present stage of development of analytical modeling in the areas covered.

Viscoelastic crack growth

The study of crack growth in a linear viscoelastic material has been motivated primarily by interest in modeling the fracture process in relatively brittle polymeric materials, although other materials may be idealized as linear viscoelastic under some circumstances. There are numerous specific linear viscoelastic models available for stress analysis, but only some general properties are considered here for crack growth analysis. Time-dependent material response, of the kind on which the theory of viscoelasticity is based, may be of interest in the analysis of fracture phenomena at two different levels. On the one hand, the bulk properties of the body in which the crack is propagating are important in determining the way in which the effect of applied loads is transferred to the crack tip region or the way in which stress is redistributed due to crack growth.