Mixed Material Point Methods for Stiff Elastoplasticity

We present a family of mixed Material Point Methods well suited for the CFL-rate simulation of stiff elastoviscoplastic materials, up to the incompressible limit. Our work builds upon the mixed discretization from Daviet and Bertails-Descoubes [2016a] and extends it to handle finite-strain vis-coelasticity and more general flow rules, allowing the simulation of a much wider range of materials. Our implicit integration scheme leads to a well-posed, symmetric optimization problem with compact stencils for which we propose an efficient GPU solver. We demonstrate our method on a variety of examples ranging from granular materials and snow to elastic solids, including two-way coupling with rigid-body solvers.