Comparative analysis of the plastic and out-of-plane constraint zones in cracked plates

In this work, the size and shape of the plastic and constraint zones are calculated along the crack front for cracked plates of different thicknesses. The extent of both zones has been compared in order to ascertain under which conditions it is appropriate to consider a pure elastic approach for the analysis of crack instability, such as that based on the first and second terms of Williams series expansion. For the sake of generality, the study is based on a dimensional analysis. The data have been obtained from 3D finite element results. For materials for which LEFM can be applied, it has been concluded that the constraint zone clearly engulfs the plastic zone (except near the free surfaces), even for thin plates whose thickness is less than the minimum plane strain thickness specified in current norms. (C) 2014 Published by Elsevier Ltd.