Research On Tillage Resistance Of Double-Wing Subsoiler Based On Discrete Element Method

Subsoiling technology is one of the technological systems of conservation tillage,which is mainly used in dry land in northern China.In recent years,in southern China represented by the farming areas,soil compaction had a certain negative impact on agricultural production.It has been a significant approach to solve these problems that exploring the feasibility of applying subsoiling technology in southern China.Existing studies have shown that the chisel-type subsoiling shovel has a very limited effect on the loosening of subsoil layer of the paddy soil under the minimum sub-soiling depth.Therefore,it is of great significance to study the deep loosening effect of double-wing subsoiling shovel with larger working width on paddy soil.The double-wing subsoiler has a larger working width,which usually means greater traction.Therefore,studying the influence of the structure parameters of the double-wing subsoiler on its operating resistance can provide a theoretical basis for the selection of the matching power of the southern subsoiler tractor and promote the application and promotion of deep subsoiling technology in southern China.In order to explore the subsoiling effect of the double-wing subsoiling shovel on the southern wet clay paddy soil,the discrete element method was used to establish a discrete element model of the subsoil layer.Taking the opening angle of the blade and the angle of entering the soil as the experimental factors,a simulation experiment was carried out to study the influence of the structural parameters of the double-wing subsoil shovel on the tillage resistance and soil disturbance.In this study,the basic physical parameters of the subsurface paddy soil were measured,and a discrete element parameter calibration method based on experimental design and aimed at viscous,elastic and plastic soils was proposed.In addition,the accuracy of predicting tillage resistance by discrete element parameters and the reliability of establishing the discrete element model of subsurface soils were verified,and the influence of subsoiling shovel structure parameters on soil bulkiness,soil disturbance coefficient,draft and vertical tillage resistance was explored.The structural parameters of the double-wing subsoil shovel were optimized,the correctness of the optimization results were verified,and the subsoil effect of the double-wing subsoil shovel after the optimized parameters was evaluated.Also,the reliability of the results of the inquiry was verified.The main conclusions were as follows:(1)Discrete element parameters are generally difficult to measure directly,and it is necessary to target the calibration test results to obtain the corresponding discrete element parameters.Selection of calibration test related to soil tillage resistance is the key to determining the accuracy of the simulation test results of subsoiling operation resistance.Thus,it is proposed to use uniaxial compression test and unconfined compressive strength test as calibration tests to calibrate the discrete element parameters of the subsurface soils of the paddy soil in southern China.Parameter calibration results show that the discrete element parameters corresponding to the measured soil viscosity,elasticity and plastic characteristics are:plastic deformation ratio of 0.3,surface energy of 19.63 J/m~2,restitution coefficient of0.37,static friction coefficient of 0.44,rolling friction coefficient of 0.12,the adhesion index of 2.69,and the tangential stiffness factor of 0.59.(2)The results of tillage resistance verification test show that the maximum error of the draft operation resistance of the simulated plough body and the measured value is 10.10 N,the average error is 2.26 N,the maximum error of the vertical operation resistance is 6.11 N,and the average error is 1.48 N.These show that the calibrated parameters have a higher accuracy in predicting tillage resistance.The penetration verification test results show that the elastic stage of the simulated soil tends to be the same,and the behavior trend of the plastic stage is the same,indicating that the established discrete element model of the subsoil layer has the same firmness as the reality.(3)The simulation test results of subsoiling operation show that,within the range of experimental factors,the blade opening angle significantly affects the resistance of the subsoiling operation,and the influence on the operation resistance is a positive effect.The opening angle of the blade and the angle of entry into the soil both significantly affect the soil bulkiness and the soil disturbance coefficient,and the influence law on the soil bulkiness and the disturbance coefficient is a linear relationship with a positive effect.The double-wing subsoil shovel mainly exerts vertical upward and operating speed forces on the soil on the upper end of the subsoil shovel within the subsoil working width,and mainly exerts a pushing force on both sides of the deep loose ditch on the soil outside the working width.(4)Parameter optimization verification test results of the double-wing subsoiling shovel show that under the same conditions,the errors of the simulation results of the soil bulkiness and the soil disturbance coefficient relative to the measured results are 57.21%and 6.2%,respectively.The total average errors of draft and vertical resistance are 35.72 N and 202.89N,respectively,and the relative errors are 9.4%and 66.9%,respectively.The evaluation results of the subsoiling effect of the double-wing subsoiling shovel of the optimized parameters are:the traction force required for every 1%of the soil bulk is 28.57 N,and the traction force required for every 1%of the soil disturbance coefficient is 8.89 N.