Implementation of a material model with shear rate and temperature dependent viscosity

A material model with shear rate and, optionally, temperature dependent viscosity was implemented. Shear rate dependence is expressed with a Yasuda function and temperature dependence with an Arrhenius function. The functions were fitted to viscosity data from oscillatory rheometry of polystyrene. Validation of the viscosity function in the material model was done with a single element with prescribed shear rate and temperature. Steady state results from a Newtonian simulation of plane Poiseuille flow with the implemented user material model were found to be identical to results from a simulation with LS-DYNA's MAT_NULL. Flow through a 4:1 contraction with shear rate dependent viscosity was simulated explicit and compressible as well as implicit and incompressible. Reasonable agreement was found for pressure loss, inlet force and outflow velocity.