Model for the deformation in agricultural and food particulate materials under bulk compressive loading using discrete element method. I: Theory, model development and validation

When bulk viscoelastic particulate materials are constrained, individual particles will move and deform as an applied load is redistributed among the particles. Discrete element method is a numerical method for studying the dynamic behaviour of particles. This paper presents basic DE modelling theories and theoretical solutions for the computation of the deformation of viscoelastic particulates under load. The theories developed are incorporated into the basic theory of the discrete element method to produce a new model suitable for investigating the deformation and resulting shape change of particles during loading. Experiments were conducted and the results used to validate simulations using the new and a standard model on particles (rubber and rapeseed) modelled as spherical objects with equivalent properties under monotonic compressive load within a bulk system. The results obtained from the experiments and simulation were compared by superimposing the images of the longitudinal sections on each other and the correspondence observed. The correspondence between the experimental and simulation results were also quantified by comparison of the 2-D bed porosity estimated from the images using an algorithm developed based on computer image processing technique. There is a very good correlation between the experimental and the predicted deformation and bed porosity values obtained with the new model at all stages of compression in comparison to the increasing divergence between experimental values and those obtained from the standard model. The predicted stress-strain values from the simulation with the new model for the compression of the assemblies were also found close to the experimental values. This shows that the discrete element method is a promising approach in the study of the behaviour of deformable soft particulates. (C) 2003 Elsevier Ltd. All rights reserved.