Determination of discrete element model parameters for a cohesive soil and validation through narrow point opener performance analysis

The discrete element method (DEM) is a powerful tool that can be used to predict soil disturbance and soil cutting forces to assist design optimisation of soil cutting tools. In this study, DEM input parameters were calibrated to model a cohesive soil (Black Vertosol of southern Queensland, Australia) using the hysteretic spring contact model, coupled with linear cohesion model, and nominal particle radius of 5 mm. DEM simulations were validated using experimental results for the effects of opener rake angle and cutting edge chamfer, and bentleg opener shank offset on no-tillage narrow point opener performance. Overall, DEM results closely agreed with experimental results and exhibited similar trends. By using particle displacement analysis to predict loosened furrow boundary, most predictions of furrow parameters namely furrow cross-sectional area, furrow width, and critical depth had relative errors ranging from 1 % to 19 %. Lateral soil throw was predicted with relative errors of 0.2 %-9 %, except for the straight opener with 45 degrees rake angle (-32 %). Ridge height was over predicted in all cases due to larger DEM particles than actual soil particles used. Relative errors of 20 %, 22 %, -31 %, and -5 % in draught were recorded for the straight openers with 90 degrees (blunt), 90 degrees (chamfered), and 45 degrees rake angles, and the bentleg opener, respectively. These results show that DEM and the input parameters determined to model the cohesive soil of this study can be used to reliably assess furrow opener performance.