1991 Volume 55 Issue 3 Pages 279-285
The dislocation groups dynamics emitted from the stressed source was analysed under the stress singularity at the crack tip. From this analysis, the mechanical significance of dislocation free zone was clarified. That is, the length of dislocation free zone (DFZ) is a function of applied stress rate, and inverse pile up against the back tip of the dislocation free zone occurs. The maximum dislocation density at the tip of DFZ was represented by the double logarithmic linear function of the length of DFZ. From this analysis, it was shown that fracture occurs within DFZ and dynamic fracture strength decreases with increasing applied stress rate. Furthermore, the scattering of the trigger point for brittle fracture in the region of brittle-ductile transition was clarified by this model and the proposed model of dislocation pile-up. These analysis enable to discriminate brittleness of materials.
