New Repo: ExaConstit

ExaConstit is a crystal plasticity finite-element methods code used to determine bulk constitutive properties of metals. It is a nonlinear, quasi-static, implicit solid mechanics code built on the MFEM library based on an updated Lagrangian formulation (velocity based). The code supports either constant time steps or user-supplied delta time steps. Boundary conditions are supplied for the velocity field applied on a surface. ExaConstit supports a number of different preconditioned Krylov iterative solvers (PCG, GMRES, MINRES) for either symmetric or nonsymmetric positive-definite systems.