A FEM/DEM adaptive remeshing strategy for brittle elastic failure initiation and propagation

This article presents an adaptive remeshing strategy between the finite element method (FEM) and the discrete element method (DEM). To achieve this strategy, an edge-to-edge coupling method based on Lagrange multipliers has been set-up to ensure the continuity of velocities at the interface. To switch from a computation initially purely FEM to a FEM-DEM one, a field transfer method was required. In particular, a displacement field transfer method has been set-up. The switching from a FEM subdomain to a DEM one is activated by a transition criterion. Each time a FEM subdomain is substituted by a DEM one, the DEM subdomain microscopic properties are set-up with respect to the subdomain geometry and desired particle refinement. This is performed thanks to the linking to the so-called “Cooker,” a tool distributed along with the GranOO Workbench. Two subdomain remeshing cases were dealt with: that of an initially FEM subdomain that is converted to DEM, and that of DEM subdomains which coalesce. A numerical test case shows that the dynamic remeshing method behaves as expected: FEM subdomains are substituted by DEM ones when the transition criterion is met, and DEM subdomains coalesce when required. The final numerical test case shows a good agreement with a crack propagation experiment of the literature, while a speedup of about 20 was observed when compared to pure DEM computation.