Development Of A New Bionic Subsoiler Based On DEM

The deep tillage technique has been widely used as a key technique of conservation tillage,but the problems such as large resistance,serious wear,and high energy dissipation have not been well solved.In this study,a new kind of bionic subsoiler was designed adopting the knowledge of reverse engineering and structural bionics,which could reduce the deep tillage resistance.The main research contents and conclusions are as follows:The wear form of Hawaii seashell surface is similar to the wear form of subsoiler and soil.Inspired by this,the study selected Hawaii seashell as the bionic prototype,and the reverse engineering method is used to extract the geometry information of the seashell surface for the design of bionic subloiler.The mathematical fitting equation based on the characteristics of the seashell surface isy(28)561.(10)101.sin[(x-668.)?/878.]and the fitting precision is 0.99154.The thickness and width of the rib were designed according to the ratio of amplitude and half cycle.Considering the geometrical parameters of the subsoiler,the bionic subloilers were designed in different elements of the rib,whose angle varies from 30°,45°and 60°,width varies from 20 mm,30 mm and 40mm,rib number varies from 4,5 and 6 respectively.There were 14 kinds of bionic subsoilers in total,which were designed according to the Hawaii seashell information.In order to compare the reduction effect of diffrent subsoilers,this study analysed the cultivation process of subsoilers with the discrete element method(DEM),so the optimal model could be selected according to the resistance reduction effects.The resistance reduction mechanism of subsoilers were discussed from the view of macro and micro angle.At the macro level,the horizontal tillage resistance and the total force of soil were compared in terms of the soil model and the subsoilers,and at the micro level,the horizontal and vertical soil particles slices were intersected to study the raised angle and velocity trajectories of the particles.The results showed that the resistance reduction effect of the bionic subsoilers were better than that of the original one.The best subsoiler was the one which has 45°rib angle,30mm rib width and 6 ribs.The simulation results were validated by the field experiments and it was showed that the original smooth subsoiler suffered the maximum resistance,and the subsoiler that was combinated by 30°in angle,20 mm in width,number of 4 ribs suffered the centered horizontal resistance;the subsoiler that was combinated by 45°in angle,30 mm in width,number of 6ribs had least resistance.The simulation value of the horizontal resistance of the three types of subsoilers were always slightly smaller than that of the field experiments.The relative errors ratio of the three models are 6.32%,10.82%and 12.46%respectively,and all the errors ratio were within the allowable range.The field experiments results showed that the soil bulk density has decreased 0.165 g/cm~3,0.196 g/cm~3 and 0.220 g/cm~3 respectively after deep tillage of the three subsoilers,while the compactness decreased 1118.1 kPa,1125.9 kPa and 1135.3kPa respectively.It was concluded that the soil bulk density and compactness decreased by the tillage of the three types of subsoilers,and the subsoiler that was combinated by 45°in angle,30 mm in width,number of 6 ribs performed the best cultivation quality therefore it had a good application prospect.This study provided a theoretical basis for the development of a new type of bionic subsoiler,and it also opened up a new way to solve the problem of large resistance and short lives for subsoilers.