On stable crack growth

B efore catastrophic fracture occurs, certain changes in the distribution of the plastic strain near the crack-tip seem to take place. These changes make crack growth possible but contribute to a gradually increasing screening of the energy flow through the plastic region towards the crack-tip. Stable crack growth results. This phenomenon appears to be a feature common to almost all fractures. Therefore, a unified theory may be developed to describe fracture at both small-scale and large-scale yielding as well as stable crack growth which is accompanied by plastic collapse rather than being superseded by catastrophic fracture. In the present paper, an attempt is made to show how such a unified theory would work.