Characterization of additive manufactured particles for DEM validation studies

Abstract

Discrete element method (DEM) simulations are often validated using physical laboratory tests on analogue soils to confirm the macro-scale response. These analogue soils have typically consisted of steel ball bearings or glass beads, thus limiting the shapes to spherical particles. Additive Manufacturing (AM) technologies can be used to create 3D objects of any shape layer-by-layer. Using these AM particles as analogue soils allows for DEM validations to be performed using a wide range of shapes, more realistically replicating natural sands and gravels. In order to use these AM particles, however, characterization of the AM material is essential to ensure its suitability for laboratory testing and to determine the intrinsic material properties input into the DEM models. This paper describes a study in which material properties and surface characteristics of two different additively manufactured materials are determined. A gypsum-epoxy composite material and a photopolymer material were tested to determine properties such as Young’s modulus, Poisson’s ratio, shape, surface roughness, and inter-particle friction angle. In comparison to the commonly used steel ball bearings and alkaline glass beads, the AM particles exhibited improved circularity. The hardness and Young’s modulus values were measured directly and then a fitting procedure was used to assess the Hertzian behavior of the spheres under uniaxial compression. While the inter-particle friction angle and the surface roughness were higher for the AM particles in comparison to the steel ball bearings and glass beads, the ability to control particle shape for the AM particles proves advantageous for manipulation of shape parameters for DEM validation.