Preliminary Investigation of Convergent Evolution-Inspired Serrated Structure for Optimization of Mini Rotavator Blade’s Cutting-Edge

Highlights An alternative bioinspired perspective that focuses on analogous geometrical features of soil animals was proposed. Reverse-engineering technique was adopted to build the virtual prototype of mini-rotavator’s blades. EDEM investigation along with soil bin experiment were conducted to evaluate blades’ performance and reveal the soil-blades interaction mechanism. The tillage tools designed by convergent evolution-inspired approach could increase their availability in underdeveloped hilly and mountainous areas. Abstract. High resistance torque and energy consumption severely limit the applications of mini rotavators in underdeveloped hilly and mountainous areas. From the perspective of convergent evolution, this study proposes an alternative optimization approach that takes a broader perspective and focuses on analogous structures of soil animal claws that serve the functions of efficient soil burrowing. Experimental investigations were carried out to test the hypothesis that serrated structures with certain geometrical parameters could have the potential of reducing penetrating resistance and improving energy efficiency of rotary soil-engaging component. By taking mini rotavator’s blade as the research object, the convergent evolution inspired serrated structures were utilized for the design of the blade’s front, side and transition cutting edge. In this investigation, five types bioinspired mini rotavator’s blades were designed and prepared, then their performances were compared with the conventional blade. By taking the length of serrated unit, rotational speed and tilling depth as experimental factors, and the resistance torque as experimental index, quadratic regression rotation orthogonal combination test was conducted. Then, the optimal parameters for the design of bionic blade were determined. Further, the performance of mini rotavator assembled with bionic and conventional blades were evaluated by EDEM. The mechanism of bionic blades for reducing resistance and improving tillage efficiency was investigated. Soil bin experiments indicated that the optimal parameters combination was length of serrated unit of 30 mm, the speed of 165 r/min, and tilling depth of 90 mm. At this condition, the average torque for bionic and conventional blade was 2.97 and 3.82 N·m, respectively. The bioinspired serrated structure reduced resistance torque by 22.25%. To further investigate the interaction behavior between soil and different types of blades, the reverse-engineering technique was used to extract the geometric characteristics and build virtual prototypes of the bionic and conventional blades. Then, the virtual prototypes of blades was meshed with tetrahedral elements. Simulation model was established based on EDEM. The variation behavior of resistance torque and three-dimensional forces of the two types of blades were analyzed. As expected, the simulation results showed that the average torque of the bionic and conventional blade was 2.84 and 3.42 N·m, respectively. EDEM evaluation derived that bioinspired blade reduced resistance torque by 17.0%. The relative error between simulation and measurement ranged between 4.58% and 11.70%, respectively. Thereby, the validity of discrete element model was verified and tillage performance were further analyzed. It was found the soil disturbance resulted from bionic blades was higher than that of conventional blades, which indicated improved tillage quality. Moreover, the breaking bonding Bonds for bionic blade was 72.8%, which was slightly inferior than conventional blades of 75.4%. But both types of blades could meet the tillage reequipment. These results validated that convergent evolution inspired bionic optimization approach has advantageous for the design of rotary soil-engaging implements for improving working quality and reducing resistance. Keywords: Agricultural machinery, Bioinspired serrated structure, Bionics, Convergent evolution, Discrete element, Mini rotavator, Reverse engineering, Soil-engaging component.