Cleavage crack growth resistance due to plastic flow around a near-tip dislocation-free region

Crack growth resistance curves are computed numerically for cases where fracture occurs by atomic separation, so that the length scale of the fracture process is typically much smaller than the dislocation spacing. Here, continuum plasticity would not give realistic stress levels near the crack tip; but plastic yielding far from the tip still adds to the fracture toughness.

The model employed makes use of a dislocation-free strip of elastic material, inside which the crack propagates, while the material outside the strip is described by continuum plasticity. The approximation involved in assuming an infinitely long strip of elastic material is evaluated by comparison with a few analyses for a short elastic strip, focusing on crack initiation.

For the long elastic strip several analyses are continued from the onset of crack growth until conditions of steady-state crack growth are reached. (C) Elsevier Science Ltd.