The Effect of Discrete Element Particle Parameters on Angle of Repose and Soil-Tool Force Simulation Results

Abstract. Modelling of soil-implement interaction is a complex process due to the variability within the soil profile, non-linear behavior of the soil and the dynamic effects of soil flow. An approach which should be able to realistically simulate the tillage process is discrete element method (DEM). To enable DEM simulations, selection of a suitable particle contact model and accurate determination of the DEM particle parameters are essential. A recent study performed by Ucgul et al. (2015) showed that using a hysteretic spring contact model integrated with a linear cohesion model has the potential to accurately model soil-tool interaction. As some DEM parameters are calibrated using the trial and error approach there can be several combinations of parameters that provide the desired angle of repose for the soil. In this study the effects of two main DEM calibrated parameters, namely; coefficient of rolling friction and cohesive energy density on the angle of repose and soil-tool force results were investigated for spherical and two sizes of clumped particles. Results showed that not all of the combinations of coefficient of rolling friction and cohesive energy density that provide the correct angle of repose can provide accurate tillage draft and vertical force predictions. The 5 mm radii spherical particle performed better than the clump particles in this study. Of the clump particles the clumps formed using 2.5 mm spheres were better than those formed using 5 mm spheres. In conclusion, two calibration tests must be performed to calibrate both angle of repose and tillage forces to ensure accurate simulations are achieved.