Development of a dual sideway-share subsurface tillage implement: Part 1. Modeling tool interaction with soil using DEM

In this research, the interactions of a dual sideway-share subsurface tillage implement with soil were modeled by discrete element method (DEM) and evaluated in an indoor linear soil bin. Spherical particles with Hertz-Mindlin contact model and parallel bond between particles were used to simulate agricultural soil aggregates and their cohesive behaviors. In soil bin experiments, soil cutting resistance and soil disturbance characteristics resulting from the tillage tool operating at 0.25 m s-1 and 150 mm cutting depth, were measured. The calibration of bond stiffness was performed through comparing the draft forces of a simple soil engaging tool simulated with DEM and those estimated with an analytical tillage modeling results using a trial-and-error method. The ratio of soil bin measured vertical force to draft force was used in calibration of the most sensitive model parameter, particle shear modulus. Its calibrated value for a sandy clay loam soil was 50 MPa. The calibrated model was validated using the soil forces as well as the soil disturbance characteristics of the tool measured in the soil bin. When comparing the model to the experimental results, the relative error was -2.0% for the average draft force, 2.5% for the average vertical force, -7.7% for the average rupture distance, and 11.7% for the average disturbed area. Therefore, good correlations were achieved between the soil mechanical behaviors obtained by the experiments and the DEM simulations. It can be concluded that in DEM simulations of some tillage tools such as subsurface tillage implement, accurate predictions of the vertical forces as well as the draft forces, could be achieved by calibrating the particle shear modulus using the ratio of vertical force to the draft force applied to the tool.