Study On LS-DYNA-Based Simulation Experiment And Its Optimization Design For Orchard Spiral Ditcher

The orchard ditching is an important working procedure for fertilization and improving the quality of fruit.It generally digs rectangle ditches on both sides of each fruit tree whose width and depth is between 0.3 and 0.4 meters.At present,there is not yet the ditcher which adapts the specific operating environment of the orchard in china.The ditching operations are mostly completed depending on manpower,which is big work intensity and low efficiency.Based on the actual demand of orchard,in this paper,an upright column-variable pitch spiral orchard ditcher was designed,and the experimental research of numerical simulation with the explicit dynamic method and its optimization design were developed.The main works were as follows:(1) An upright column-variable pitch spiral orchard ditcher and an equipment of soil-bin test were designed.Aimed at orchard production requirements,the working principle and the main structure about the upright column-variable pitch spiral orchard ditcher were proposed.The spiral ditcher was mainly composed of Dongfeng-12 walking tractor,combination of screw axis,combination of baffle,double output speed reducer and the main frame,etc.The main structural parameters and performance parameters were analyzed and determined:with the small farm tractor as the driving force,pure-hour production efficiency of ditcher is not less than 80 m/h,and the ditch type is rectangular with 0.3m depth,0.3m width.At the same time,a device specialized in soil-bin functional trial was developed.(2) The mechanical properties of spiral furrow opener were analyzed and the soil-bin test was carried out.It mainly contained:1)The molding and unwrapping algorithm of the core components of furrow opener-helicoids were analyzed;2) Under the condition of idealized assumptions,the kinematics and dynamics model for the soil particles and spiral cutter in cutting process were established.The decomposition velocity in every direction and the force condition for each plane about the being cutting soil particles were analyzed, and the critical rotational speed was obtained;3) The matching relationship between geometric parameters and motion parameters of the spiral orchards ditching cutter were researched;4) The functional trials of the test device were carried out on high-speed digital soil-bin test platform,and the experimental result was that the upright column spiral furrow opener could dig rectangular ditch with the 0.3m width and 0.10 to 0.35m depth when the forward speed was 0.0278 m/s and the rotation speed was 240 r/min;the ditch wall and bottom were more leveling up,and the dropped soil in ditch was less than other furrow openers ditching.(3) The numerical simulation of spiral furrow opener cutting soil was developed based on ANSYS/LS-DYNA.It mainly contained:1) The constitutive model and the parameter value of the soil MAT147(MAT_FHWA_SOIL) adapted to soil cutting numerical simulation was analyzed and determined.2) The finite element model of spiral cutter cutting soil was established.We could get conclusions as following:based on ANSYS/LS-DYNA,the established three-dimensional dynamic simulation model of the spiral cutting tool cutting soil,could effectively reveal the working process of cutting; adopted the modified Drucker_Prager plastic soil model made simulation calculation successful and it was suitable for the soil cutting explicit dynamic analysis;by the calculation of cutting energy consumption in the process of cutting,we could gain the maximum power of 3.7 KW,thus the finite element model could be used to estimate the value of cutting power consumption and guide ditching power selection;at the same time, through the analysis of Von Mises stress change rules and mechanical properties of the spiral vanes in the process of cutting could provide the basis for the determination of structural parameters of the spiral cutter.(4) The experimental study of spiral cutter cutting soil and parameters optimization were developed.Combined with orthogonal experiment designing and SAS software applied,the regression analysis of the main experimental factors about forward velocity v, rotation speedω,structural parameters of spiral vane e was developed and the regression equation was established.We could conclude that the influence of v andωto the power consumption were significant and e to the power consumption was very significant.At the same time,for optimizing the parameters of spiral cutter,taking regression equation as objective function,taking the requirements of minimum productivity,maximum power consumption,critical speed,the distance of soil casting as constraint,the optimal mathematical model of the main parameters was established.Aiming at design example, the model was optimized with the toolkit of MATLAB.We could conclude that the minimum power consumption of cutting was 2.3836KW when v was 0.0278m/s, k₀ 1.2286,tgα₀ 0.1763,ω13.9671rad/s.