Microstructurally induced computational and material instabilities

A dislocation-density based finite strain crystal plasticity finite element model and an hourglass strain measure orthogonal to the linear velocity field were used to investigate microstructural effects on deformation and hourglass instability. An aluminum aggregate was modeled in quasi-static plane strain tension and compression, and the effects of the presence of manganese-based dispersed particles were investigated. Both local plastic deformation and the presence of these dispersed particles can trigger hourglass instabilities, which can be mistaken for deformation or failure modes. These hourglass modes occur due to the difference in the deformability of neighboring elements or regions and the associated energy modes associated with hourglassing, and the proposed computational methodology can be used to delineate between failure modes and numerical instabilities.