Dislocation based Gradient Plasticity Theory

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This project aims at the extension of the small strain gradient crystal plasticity framework, which has been developed through the first funding period, to large deformations. Similar to the smallstrain framework, the large-strain framework is then coupled to CDD-theory which incorporates dislocation transport terms. By such an approach a gradient crystal plasticity theory is linked to CDD thereby closing the latter constitutively. This extended type of gradient theory is expected to reproduce size effects in oligocrystals induced by both a size-dependent bulk behavior and grain boundary effects. Additionally, the second period aims at extension of the developed elastic-plastic grain boundary model by introducing an orientation dependence of the plastic grain boundary terms (like the resistance against plastic flow) on e.g. the orientation of the grain boundary and the crystal orientations of the adjacent grains. Here, also a geometrically nonlinear efficient extension of the developed elastic-plastic grain boundary model for finite deformations is planned. A broad variety of applications is intended by comparing the simulation results to experiments (bending of micro-beams, torsion of thin wires, tensile tests) as well as benchmark simulations, e.g. from DDD.