Dresden 2006 – scientific programme

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MM: Metall- und Materialphysik

MM 34: Symposium Materials Modelling III

MM 34.7: Talk

Thursday, March 30, 2006, 18:30–18:45, IFW A

A grain boundary mechanism for nonlocal constitutive laws in crystal plasticity finite element simulations — •Anxin Ma, Franz Roters, and Dierk Raabe — Max Planck Institut für Eisenforschung, Max-Planck-Str. 1, 40237 Düsseldorf, Germany

When the simulation scale in crystal plasticity becomes small such as in studies focused on the grain boundary region, nonuniform plastic deformations occur commonly which can cause non ignorable orientation gradients for a bulk material point in an infinite small neighborhood, and furthermore a certain number of additional dislocations have to be introduced to preserve the lattice continuity. Furthermore if studies are focused on the grain boundary zone, interactions between mobile dislocations and grain or phase boundaries have to be introduced into constitutive models to reflect the constraint relation between a grain or phase boundary material point with its neighborhood. Based on experimental findings, a grain boundary constitutive mechanism is proposed to consider interactions between two abutting crystals. In this mechanism an additional energy barrier coming from slip transmissions at grain boundaries is added to the general activation energy of dislocation slips in the bulk crystal to capture the thermal activated penetration event in the grain boundary zone. The approach is based on a conservation law for the Burgers vector loop around the interface affected. Furthermore a special grain boundary finite element is introduced in numerical simulations of three bicrystals with small, middle and large angle flat grain boundaries. The hardening effect of grain boundaries, strain distribution and texture evolution of bicrystals are discused carefully.