A new contact model for modelling of elastic-plastic-adhesive spheres in distinct element method

Rigorous models of elasto-plastic contact deformation are time-consuming in numerical calculations for the Distinct Element Method and quite often unnecessary to represent actual contact deformation of common particulate systems. In this work a simple linear elastic-plastic-adhesive contact model for spherical particles is proposed, whereby the loading cycle is a linear plastic deformation and the unloading is elastic with a higher stiffness compared to the plastic deformation. The adhesive behaviour is considered once the unloading contact force reaches the pull-off force, at which point the contact deforms with negative elastic-adhesive stiffness. In order to account for increase in adhesion due to plastic deformation, the pull-off force is evaluated using negative linear plastic-adhesive stiffness. The model is applied to compression of spherical particles with elastic-plastic-adhesive contacts for which sensitivity analyses of the model parameters on work of compaction are carried out. As the ratio of elastic to plastic stiffness is increased, the plastic component of the total work increases for a given strain and the elastic component decreases. Large stiffness ratio values imply particles undergoing larger plastic work for a given strain. By increasing interface energy, the plastic work increases for a given solid fraction, however the elastic work does not change. In this case, the maximum tensile force is increased therefore the work of adhesion is increased.