Effect of stress triaxiality on void growth in dynamic fracture of metals: A molecular dynamics study

E. T. Seppälä, J. Belak, and R. E. Rudd
Phys. Rev. B 69, 134101 – Published 1 April 2004
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Abstract

The effect of stress triaxiality on growth of a void in a three-dimensional single-crystal face-centered-cubic lattice has been studied. Molecular dynamics simulations using an embedded-atom potential for copper have been performed at room temperature and using strain controlling with high strain rates ranging from 107/sec to 1010/sec. Strain rates of these magnitudes can be studied experimentally, e.g., using shock waves induced by laser ablation. Void growth has been simulated in three different conditions, namely, uniaxial, biaxial, and triaxial expansion. The response of the system in the three cases has been compared in terms of the void growth rate, the detailed void shape evolution, and the stress-strain behavior including the development of plastic strain. Also macroscopic observables as plastic work and porosity have been computed from the atomistic level. The stress thresholds for void growth are found to be comparable with spall strength values determined by dynamic fracture experiments. The conventional macroscopic assumption that the mean plastic strain results from the growth of the void is validated. The evolution of the system in the uniaxial case is found to exhibit four different regimes: elastic expansion; plastic yielding, when the mean stress is nearly constant, but the stress triaxiality increases rapidly together with exponential growth of the void; saturation of the stress triaxiality; and finally the failure.

  • Received 22 October 2003

DOI:https://doi.org/10.1103/PhysRevB.69.134101

©2004 American Physical Society

Authors & Affiliations

E. T. Seppälä, J. Belak, and R. E. Rudd

  • Lawrence Livermore National Laboratory, Condensed Matter Physics Division, L-415, Livermore, California 94551, USA

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Vol. 69, Iss. 13 — 1 April 2004

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