Avalanches in 2D dislocation systems: Plastic yielding is not depinning

Ispánovity, Péter Dusán and Laurson, L. and Zaiser, M. and Groma, István and Zapperi, S. and Alava, M. J. (2014) Avalanches in 2D dislocation systems: Plastic yielding is not depinning. PHYSICAL REVIEW LETTERS, 112 (23). ISSN 0031-9007

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Abstract

We study the properties of strain bursts (dislocation avalanches) occurring in two-dimensional discrete dislocation dynamics models under quasistatic stress-controlled loading. Contrary to pre- vious suggestions, the avalanche statistics differs fundamentally from predictions obtained for the depinning of elastic manifolds in quenched random media. Instead, we find an exponent τ = 1 of the power-law distribution of slip or released energy, with a cut-off that increases exponentially with the applied stress and diverges with system size at all stresses. These observations demonstrate that the avalanche dynamics of 2D dislocation systems is scale-free at every applied stress and, therefore, can not be envisaged in terms of critical behavior associated with a depinning transition.

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