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Effect of Crack Blunting on the Ductile-Brittle Response of Crystalline Materials

Published online by Cambridge University Press:  15 February 2011

D.M. Lipkin ,
G.E. Beltz  and
L.L. Fischer
D.M. Lipkin
Affiliation:
Physical Metallurgy Laboratory, GE Research & Development Center, Niskayuna, NY 12309
G.E. Beltz
Affiliation:
Department of Mechanical and Environmental Engineering, University of California, Santa Barbara, CA 93106-5070
L.L. Fischer
Affiliation:
Department of Mechanical and Environmental Engineering, University of California, Santa Barbara, CA 93106-5070
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Abstract

We propose a self-consistent criterion for crack propagation versus dislocation emission, taking into account the effects of crack-tip blunting. Continuum concepts are used to evaluate the evolving competition between crack advance and dislocation nucleation as a function of crack- tip curvature. This framework is used to classify crystals as intrinsically ductile or brittle in terms of the unstable stacking energy, the surface energy, and the peak cohesive stresses achieved during opening and shear of the atomic planes. We find that ductile-brittle criteria based on the assumption that the crack is ideally sharp capture only two of the four possible fracture regimes. One implication of the present analysis is that a crack may initially emit dislocations, only to reinitiate cleavage upon reaching a sufficiently blunted crack-tip geometry.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 539: Symposium M – Fracture & Ductile vs. Brittle Behavior - Theory, Modelling… , 1998 , 49
Copyright
Copyright © Materials Research Society 1999

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