Molecular dynamics investigation of dynamic crack stability
- Max-Planck-Institut fuer Metallforschung, Institut fuer Werkstoffwissenschaft, Seestr. 92, 70174 Stuttgart (Germany)
- Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
A series of molecular-dynamics simulations has been performed in order to evaluate the effects of several physical factors on dynamic crack stability. These factors are the crystalline structure and the interatomic interaction modeled by various empirical potentials. For brittle crack propagation at low temperature we find that steady-state crack velocities are limited to a band of accessible values. Increasing the overload beyond K{sub Ic}, the crack can propagate with a steady-state velocity, which quickly reaches the terminal velocity of about 0.4 of the Rayleigh wave speed. The magnitude of the terminal velocity can be related to the nonlinearity of the interatomic interaction. Further increasing the overload does not change the steady-state velocity dramatically, but significantly increases the amplitude of acoustic emission from the crack tip. Loading the crack even further leads to instabilities which take the form of cleavage steps, dislocation emission, or branching. The instability is closely related to the buildup of a localized coherent, phononlike field generated by the bond-breaking events. The form of the instability depends critically on crystal structure and on the crystallographic orientation of the crack system but can also be correlated with the relative ease of dislocation generation (and motion). {copyright} {ital 1997} {ital The American Physical Society}
- OSTI ID:
- 450381
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 55, Issue 6; Other Information: PBD: Feb 1997
- Country of Publication:
- United States
- Language:
- English
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