On the implications for LEFM of the three-dimensional aspects in some crack/surface intersection problems

Abstract

Several elastic configurations containing cracks under transverse tension which intersect a free surface are investigated. In order to ensure reliable results two independent numerical methods are employed on a comparison problem, each method being tuned to handle the special features involved. The comparison provides confidence in other results which focus on the key quantity in linear elastic fracture mechanics, the energy release rate. These findings may be summarized as follows: that the decays in the energy release rates found as the free surface is approached in the various problems treated are probably not significant from a fracture toughness testing point of view and not of major consequence in cyclic life calculations, although there are some indications that this may not be the case if near-surface residual stress fields are present; and that these variations in energy release rate can be compensated for by relatively minor perturbations in crack-front profiles.