ABSTRACT
In this chapter ، a fundamental approach to fracture will be followed in order to develop a few central ideas about why any given material is ductile or brittle ، and how the basic lattic defects of the material cooperate to give rise to these two general classes of behavior . The analytical discussion will tend to focus on relatively brittle phenomena ، partly because any idealization of fracture – leads one first to the consideration of brittle fracture and partly because the analysis for brittle fracture is better understood and therefor more accessible .