  We present a wrapper that allows Abaqus user material subroutines (UMATs) to
be used as an External Material library in the software COMSOL Multiphysics.
The wrapper, written in C language, transforms COMSOL's external material
subroutine inputs and outputs into Fortran-coded Abaqus UMAT inputs and
outputs, by means of a consistent variable transformation. This significantly
facilitates conducting coupled, multi-physics studies employing the advanced
material models that the solid mechanics community has developed over the past
decades. We exemplify the potential of our new framework, UMAT4COMSOL, by
conducting numerical experiments in the areas of elastoplasticity,
hyperelasticity and crystal plasticity. The source code, detailed documentation
and example tutorials are made freely available to download at
www.empaneda.com/codes.
