Performance Evaluation of Jerusalem Artichoke Digging Tool in Cohesive Soil Using Discrete Element Method

Abstract

Highlights Response surface methodology is suitable for DEM input parameter optimization. Soil reaction forces reduced at velocity ratios greater than one (1.2-3.9). Vibration reduced soil reaction forces at the target depth of 350 mm by 70%. In general, soil reaction forces increase with speed but decrease with frequency. Abrasive wear predominantly occurred at the tool’s cutting section. Abstract. The discrete element method (DEM) and response surface methodology (RSM) were used to determine the input parameters and combination of operational factors required for optimizing the Jerusalem artichoke (Helianthus tuberosus L.) harvesting tool in cohesive soil. The DEM soil model consisted of particles with different radii in three shapes calibrated using angle of repose and cone penetration data. Compared with data from a soil bin subsoiler evaluation, the DEM model showed acceptable relative errors for draught force (6.7%), vertical force (4.5%), and furrow width (9.3%). The effects of operational factors, including forward speed, vibration frequency, and amplitude, on response variables such as draught and vertical forces, drawbar power, and abrasive wear were analyzed for three harvesting shovels (S-shape, step-shape, and fork-shape). The ratio of vibratory speed to forward speed (velocity ratio, Vr) was used to analyze the combined effect of the factors. The operational factors significantly affected all the response variables (p<0.05). At Vr > 1 (1.2-3.9), soil reaction forces and drawbar power were considerably reduced. The optimal parameters for minimizing the response variables were 2.5 km h-1 forward speed, 14.5 Hz frequency, 30 mm amplitude, and S-shape shovel at Vr = 3.9. The minimum draught force, vertical force, drawbar power, and Archard wear depth were 4.64 kN, 0.41 kN, 2.64 kW, and 2.36 mm, respectively, at an operating depth of 350 mm. Operating in vibratory mode reduced draught force by 54% with the full width of the implement. Future work should include Jerusalem artichoke tubers in the simulation and experimental validation. Keywords: Abrasive wear, Clay, Numerical optimization, Soil reaction forces, Velocity ratio, Vibration.