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Free keywords:
Deep drawing; Dislocations (crystals); Drawing (forming); Microfabrication; Plasticity; Plasticity testing; Single crystals; Size determination, Crystal plasticity; Dislocation densities; Micro forming; Physically based modeling; Size effects, Forming
Abstract:
Due to size effects, the conventional material constitutive models are no longer valid in the investigation of micro-forming processes. In this work, a nonlocal physically based crystal plasticity FEM is developed to investigate the size effects of micro-forming. Except for statistically stored dislocations, geometrically necessary dislocations on the slip systems are introduced and calculated via the mesh-free paradigm. The micro-tensile and micro-deep drawing experiments of polycrystalline copper foils with different thicknesses and grain sizes are used to calibrate the presented nonlocal model. The comparison between simulations and experiments shows that the nonlocal physically based crystal plasticity FEM is capable of describing both the first order and the second order size effects of the micro-forming processes, and providing more microstructural clues for the interpretation of these size effects. Furthermore, the simulations of micro-deep drawings demonstrate that the presented nonlocal method is robust in the simulations with complex contact boundary conditions. © 2015 Elsevier B.V.
