Parametric analysis and numerical optimisation of Jerusalem artichoke vibrating digging shovel using discrete element method

Abstract

Commercial potato harvester is inefficient in harvesting Jerusalem artichokes due to the vast development area of tubers in the soil and the wide-ranging sizes and shapes, some growing up to a depth of about 35 cm. Harvesting artichoke tubers, mainly at such deep depth, is problematic, necessitating optimisation of parameters for the harvesting operations to account for the effect of soil-tool dynamics on the digging performance. However, vibration can substantially reduce soil reaction forces and increase the soil-crushing effect, improving harvesters’ production efficiency. Therefore, the effect of travel speed, vibration frequency, amplitude, and rake angle and the shovel geometry on soil reaction forces, drawbar power, and Archard wear were studied using the discrete element method (DEM) and response surface methodology (RSM) at a targeted shovel’s operating depth of 35 cm. Laboratory experiments of the static angle of repose and cone penetration tests were successfully used to calibrate the soil model using multi-sphere particles. Also, Design-Expert® Software (2021) version 13 was used to determine the optimised geometry design and operating parameters values from the soil-to-shovel interaction simulation based on numerical optimisation and desirability functions procedure. Two optimal solutions were obtained, with the first one having 0.556 m s− 1 speed, 13.864 Hz frequency, 20 mm amplitude, 15˚ rake angle, and S-shape geometry. Contrariwise, the second solution was at the same geometry design with 1.111 m s− 1 speed, 20.300 Hz, 20 mm amplitude, 15˚ rake angle. Analysis of variance showed that all the individual factors influenced draught force, vertical force, and drawbar power. However, only frequency, amplitude, and geometry design significantly influenced Archard wear. Soil reaction forces increased with increasing speed. Vibration significantly affected soil reaction forces by reducing draught force and vertical force by 43.61% and 36.67%. DEM and RSM are effective techniques for designing and optimising soil-engaging implements.