Abstract A theory which includes first and second strain gradients is proposed as a model for plastic deformations. Heuristic arguments for including the gradients are also given. The main goal is to develop a logical framework in which behavior on a small scale can interact with the response on a larger one. The gradients lead to deformations which contain oscillatory components in addition to the ones obtained without them. For a particular material, these oscillatory deformations develop only during plastic deformations. They contain many of the properties that one would expect of the continuum analogue of dislocations. As contrasted with the theory of the continuous distribution of dislocations, the proposed theory applies to the entire plastic deformation process.
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