Modelling adhesive contact between fine particles using material point method

This paper presents a numerical study on contact law between extremely fine particles taking into account of the effect of adhesion force and surface roughness. The adhesion force between two particles is calculated from the Erkoc inter-atomic potential. This force is incorporated into a material point model for the dynamic impact between the two particles. Unlike a molecular dynamics model, atoms in the model are embedded in the continuum solid such that they can only move relatively to each other as the continuum solid deforms. The model is numerically efficient while taking into account of the adhesion effect at the same time. Numerical study using this model shows that the Maugis theory ( Maugis, 1992) is valid for spherical particles as small as 50 nm in size. The numerical study also shows that a slight change in surface roughness can alter the impact behaviour completely. Therefore an uncertainty in using the Maugis contact law for real particles is how to determine the effective specific surface energy for particles of different surface roughness. Because of the uncertainty, full numerical analysis may have to be used to obtain the adhesive contact law.