Effect of plasticity on cleavage crack growth resistance at an interface

The mixed mode toughness of an interface joining an elastic-plastic metal t o a solid which does not yield plastically is studied numerically for cases where fracture occurs by atomic separation. Thus, the length scale of the fracture process is typically much smaller than the dislocation spacing on the metal side of the interface. But even though the crack growth mechanism is brittle, the interface shows crack growth resistance due to plastic flo w at some distance from the crack tip. It is assumed that the crack tip doe s not emit dislocations. Therefore, the numerical technique employed makes use of a thin elastic strip of material along the metal side of the crack t ip, while the metal outside the strip is described by continuum plasticity. Most of the computations use an infinitely long elastic strip to represent the elastic core region around the tip, but the approximation of using a l ong strip is tested by comparison with a few analyses for a short strip. (C ) 1999 Elsevier Science Ltd. All rights reserved.