Linking material models between codes: establishing thermodynamic consistency

One increasingly important workflow for multiphysics simulations is linking simulation codes that have different physics models and different regimes for which they have been optimized. The science question for this scoping work was evaluating the compatibility of physics models on both sides of a link to ensure a smooth simulation continuation was possible. The VVUQ aspects were establishing the most important physics aspects for a credible simulation. The most important aspect was determined to be thermodynamic consistency such that nothing unphysical would be encountered during the simulation. The second most important aspect is ensuring adequate handling of mechanical deformation. The specific problem was driving a Taylor cylinder into an infinitely hard wall. The material was cerium, which has a complicated enough phase diagram to show some interesting thermodynamic behavior during the deformation. The main software involved is Abaqus for the initial simulation, Zelda (a LANL code) for linking, and FLAG (a LANL Lagrangian finite volume code). The basic process is using nominally the same material models in both Abaqus and FLAG to: perform a calculation in Abaqus output an ODB file from Abaqus with fields (e.g., density, stress) use Zelda to extract fields and remap them onto a new mesh suitable for FLAG continue the simulation in FLAG The remapping of fields onto the new mesh is a negligible source of error. Thermodynamic consistency is a much larger source of overall error and can be large enough to prevent initialization in the receiving code. The situation arises because of the way that the two codes treat different fields. Both codes have interpolation processes for evaluating the thermodynamics. Differences in which variable is primary and which is interpolated lead to numerical errors that can be irrelevant in one code and unusably large in the other code. This paper will explain the VVUQ issues in linking the codes, even with nominally the same material models, and propose some activities to answer some important VVUQ questions.