Faster and objective level set-DEM mechanical simulations of discrete systems with convex particles from contact history and particle surface considerations

Aiming for versatile simulations of the mechanics of discrete systems with arbitrary convex particles, an extended Level Set (LS) description of particle shape is proposed in the framework of the Discrete Element Method (DEM). The LS shape description as a discrete field of the signed distance function is first obtained with a faster initial generation and then proposed to directly output particle surface in a validated workflow. It mostly includes an innovative optimization for the surface nodes discretization which combines with the LS distance field for DEM contact treatment. In their optimized definition, surface nodes locate in a nearly uniform fashion over a particle and are handled in a sparse manner during contact treatment, thanks to an original consideration of contact history. As such, computation speed gains are reported with a factor of more than 3 during simulations of quasi-static mechanical loading. The proposed nodes definition is also shown to be instrumental to insure objectivity of the LS contact model and DEM simulations. The present LS approach is finally applied to a preliminary study of the residual shear strength of various packings made of superquadrics all sharing the same shape. After a justification of the chosen particle number to form a Representative Elementary Volume, the shear strength is shown to lack a clear relationship with Wadell's true sphericity as a shape index, while being possibly 73% higher than the one obtained with spherical particles.