The mode-I fracture behavior in face-centered cubic and body-centered cubic materials was analyzed by using the discrete dislocation approach. Dislocations were modeled as line discontinuities in an isotropic linear-elastic medium which interacted with each other via long-range stress fields. The short-range reactions which underlay dislocation nucleation and annihilation were also introduced in order to permit simulation of the changes in dislocation structure during loading. The motion of dislocations and their nucleation were considered to be controlled by thermal activation at higher temperatures and lower stress levels, and by phonon-drag at lower temperatures and higher stress levels. A mode-I crack was introduced into the model by using a cohesive surface formulation. The results obtained showed that differences in the orientation of the slip planes, relative to the low cohesive-strength {100} fracture planes, caused dislocations to promote crack-tip blunting and plastic shielding in the case of face-centered cubic materials while such effects were only minor in the case of body-centered cubic materials. The temperature was found to have a marked effect upon the fracture toughness of body-centered cubic materials, whereas its role in the case of face-centered cubic materials was very small.

A Comparison of Mode-I Fracture Behavior of FCC and BCC Metallic Materials - a Discrete Dislocation Analysis. D.Columbus, M.Grujicic: Applied Surface Science, 2001, 180[1-2], 138-61