Numerical simulation of mechanical resistance of wet and dry powder cakes

Abstract

This paper presents a multi-scale modelling approach to describe the mechanical behaviour of caked powders as an aid to properly design and analyse the results of laboratory caking tests to assess the propensity of powders to cake. This approach is based on the integration of particle-particle interactions due to liquid or solid bridges over the total volume of a cake using Discrete Element Method (DEM). The overall objective of the study was to simulate the behaviour of agglomerated (caked) samples subjected to a mechanical, compressive or tractive, stress. First, simulations were performed on an assembly of particles subjected to capillary forces. The capillary forces being amenable to a theoretical description, the tensile strength of wet agglomerates was calculated theoretically and used as a reference to validate the numerical results. Simulations were based on the combination of conventional DEM method and the phenomenological model of capillary condensation. The stress-strain curves were then simulated and compared to the theoretical values predicted by Rumpf's model for wet agglomerates. After validation, numerical simulations were used to study the mechanical behaviour of wet or dry agglomerates subjected to compression. In order to take into account the cohesive effect of solid bridges at the level of elementary contacts in discrete modelling, an original Euler-Bernoulli type beam model between particles in contact was established. The simulated stress-strain results was in very good agreement with experimental data.