Random Normal Contact Laws for Particles with Rough Surface in Discrete Element Modelling
Tingting Zhao  1@  , Jun Kato  1@  , Y T Feng  1@  
1 : Zienkiewicz Centre for Computational Engineering
College of Engineering, Swansea University -  United Kingdom

Particles are assumed smooth in classical discrete element modelling (DEM), but real particles have random rough surfaces which may influence their mechanical properties. It is necessary therefore to quantitatively improve the conventional discrete element model by taking the surface roughness into consideration. In this work, two new normal contact laws are established for particles that have random rough surfaces. The contact laws are derived by both the single scale and the multi-scale methods. The single scale contact law is based on the classic Greenwood and Williamson model. Instead of a complicated integral expression involved, we develop a simple empirical formula to calculate the normal contact force between rough particles. The multi-scale contact law is based on a fractal surface model in which a circular Koch curve is proposed to represent the rough surface. The relationship of its characteristics with the main statistical properties of a real surface is also established. The both contact laws are incorporated into a DEM code to investigate the effect of particle surface roughness on the mechanical response of particle assemblies.

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