Abstract
The changes in atomic structure around the crack-tip in FCC crystal under in-plane shear (Mode II) loading is analyzed by means of molecular dynamics (MD) simulation. The interatomic force interaction is assumed to be derived from the “N-body” potential proposed by Ackland et al. The crack is modeled as a vacancy sheet and fixed boundary condition is adopted. The ductile deformation with emission of edge dislocations from crack-tip is observed. The moment at which the crack-tip atom overcomes the potential barrier and an edge dislocation is generated is clearly defined as the time when the slope of the curve of the work vs. time suddenly falls down. From the result of MD-simulation in low temperature, the critical stress intensity factor KcrII for the dislocation nucleation which is estimated with this condition agrees well with Rice's theoretical prediction. At finite temperature T, the temperature dependence of the critical stress intensity factor is able to be explained from the properties of thermal activation process. Discrete jumps are recognized in KcrII-T relation in the cases of same reference velocity. The discrete jump seems to relate the interaction of different modes of atomic vibration under the effect of shear stress in slip plane and tension-compression stress wave.
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