Deformation and failure of bulk nanograined and ultrafine-grained materials

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Deformation and failure mechanisms of bulk nanostructured materials as first observed and modeled by the Michigan Tech group are briefly discussed in the light of more recent developments. These observations and initial discrete models motivate the formulation of an extended continuum mechanics framework to capture deformation and fracture at the nanoscale. It is shown, in particular, that higher-order strain gradients enter naturally into the standard equations of continuum mechanics as a consequence of the mechanical interaction between "bulk" and internal or external "surface" points. Since these interactions become more dominant, as the dimensions of the sample decrease, it may be argued that the resultant gradient-dependent equations of elasticity and plasticity may be used for describing the behavior at the micro and nanoregime; in particular, the mechanical response of ultrafine-grained materials and nanograined polycrystals. Some examples and benchmark problems based on such modified equations of elasticity (micro/nanoelasticity) and plasticity (micro/nanoplasticity) for addressing the mechanical response of materials at the submicron regime are discussed. © 2008 Elsevier B.V. All rights reserved.

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Materials Science and Engineering A