EFFECT OF CONSTRAINT ON FRACTURE CONTROLLED BY STRESS OR STRAIN

To interpret fracture of solids, an appropriate fracture criterion is required. It is often believed that the level of strain ahead of a cra ck tip controls the fracture event for materials exhibiting high ducti lity, e.g. ductile fracture of A533B steel in the upper shelf regime. And the level of stress ahead of a crack tip controls the brittle frac ture event, e.g. cleavage fracture of A533B steel in the lower shelf r egime. Within each regime (ductile or brittle), the level of constrain t of a specimen or structure determines the magnitude of the apparent fracture toughness. In this paper, we address the difference in the ef fect of constraint on the stress- or strain-controlled fracture. It is found that the constraint plays an opposite role to the apparent frac ture toughness values for strain-controlled vs, stress-controlled frac ture. (C) 1998 Elsevier Science Ltd. All rights reserved.