Randomness and Slip Avalanches in Gradient Plasticity

Document Type

Article

Publication Date

8-2006

Department

Department of Mechanical Engineering-Engineering Mechanics

Abstract

While localization of deformation at macroscopic scales has been documented and carefully characterized long ago, it is only recently that systematic experimental investigations have demonstrated that plastic flow of crystalline solids on mesoscopic scales proceeds in a strongly heterogenous and intermittent manner. In fact, deformation is characterized by intermittent bursts ('slip avalanches') the sizes of which obey power-law statistics. In the spatial domain, these avalanches produce characteristic deformation patterns in the form of slip lines and slip bands. Unlike to the case of macroscopic localization where gradient plasticity can capture the width and spacing of shear bands in the softening regime of the stress-strain graph, this type of mesoscopically jerky like localized plastic flow is observed in spite of a globally convex stress-strain relationship and may not be captured by standard deterministic continuum modelling. We thus propose a generalized constitutive model which includes both second-order strain gradients and randomness in the local stress-strain relationship. These features are related to the internal stresses which govern dislocation motion on microscopic scales. It is shown that the model can successfully describe experimental observations on slip avalanches as well as the associated surface morphology characteristics.

Publisher's Statement

© 2006 Elsevier Ltd. All rights reserved.

Publication Title

International Journal of Plasticity

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