The crack opening area when there is limited plasticity

Abstract

The paper is concerned with the accuracy of the effective elastic crack procedure as it is applied to determining the crack opening when there is limited plasticity, in the context of formulating a leak-before-break case for a component in a pressurized system. In strict terms, the procedure is appropriate with regard to the stress and displacement fields at large distances from a crack tip. However, the crack opening area is associated with the displacement of the crack faces at positions which are in fact close to a crack tip. This means that one should question the use of the effective elastic crack procedure, as it is applied to crack opening area calculations. The present paper focusses on this issue, and by analysing a specific simple model, in fact shows that the procedure gives very accurate crack opening area predictions up to high applied loading levels. On this reckoning, it would seem that the procedure can indeed be used with confidence in leak-before-break considerations.