Study On Reducing Adhesion And Resistance And Simulation Analysis About Ditching And Rotary Soil Engaged Tools For Rape Planter

Rape is an important oil crop in China and its planting area and total production are both first in the world.It is the development tendency to develop the oilseed mechanization planting as it needs a lot of labors in the traditional planting processes.Ditching is needed when to plant the oilseed rape as there is plentiful rain in Yangtze River region.It will affect the operation qualities and operation efficiency of ditching equipment and rotatory equipment of rape seeder very much because of the clay soil and large quantity of rice straw existed in the field.In this doctoral dissertation,study on reducting adhesion and resisitance and simulation analysis about ditching and rotary soil engaged tools for rape planter was conducted and the main research conclusions are as following:(1)Soil physical properties and rice straw properties were tested and analyzed.The soil physical properties values of bulk density,moisture content,particle density,void ratio,limitation moisture content(liquid limit and plastic limit),natural slope,particle size,soil strength,adhesion,internal friction angle and the rice straw physical properties values of height,quantity,moisture content were obtained.It showed that the soil texture was loam sandy soil and the value of soil moisture content should be less than 25% when the soil engaged tools were operated in the field.The ability to adapt the operation situation that plentiful rice straw which was very hard to be chopped was existed shoule have for soil engaged tools.The factors to influence the operation resistance and power consumption of moldboard plow were analyzed and the quantitative relation between operation resistance,power consumption and soil physical properties,structure parameters of moldboard plow,operation parameters of moldboard plow,resperctively were acquired.The factors to influence the power consumption of rotary equipment were analyzed and the quantitative relation between power consumption and soil physical properties,structure parameters of rotary equipment,operation parameters of rotary equipment was acquired.(2)The soil prediction modle was established and the soil physical properties were predicted.By using the software LS-Dyna,the soil constitutive model was obtained with Drucker-Prager as the yield criterion and Mohr-Coulomb as the failure criterion.The cone resistance force-displacement curves were acquired by simulating the process of standard cone penetrating into soil.The regression models between cone resistance force-displacement curves and soil void ratio e*,internal friction angle ?,cohesion c,soil hardening parameter ? in different displacement were established and the conclusion of internal friction angle ?,cohesion c,soil hardening parameter ? affecting the cone resistance force-displacement curves value significantly and void ratio e* affecting the curve value unsignificantly was obtained.The cone resistance force-displacement curves could be fitted using two pieces curves(a parabola y=ax2 and a straight line y=kx+m)and the majority values of determination coefficient were larger than 0.99.The forth order response surface model between coefficient a?k?m and soil physical properties internal friction angle ?,cohesion c,soil hardening parameter ?,respectively both in calibration set and validation set were analyzed,with the values of determination coefficient all larger than 0.96.Using the searching algorithm to predict the values of cohesion c,soil hardening parameter ?,the value of determination coefficient was 0.85 and the value of root-mean-square error(RMSE)was 17.96% for cohesion and the counterpart values for soil hardening parameter were 0.78 and 33.90%,respectively in calibration set,while the value of determination coefficient was 0.89 and the value of RMSE was 18.03% for cohesion and the counterpart values for soil hardening parameter were 0.76 and 22.31%,respectively for soil hardening parameter in validation set.(3)The surface analysis and resistance charcter experiment of front ditching plow for rapeseed planter were conducted.A moldboard front ditching device containing plough body leg,plough surface and plough share was designed.The change rules of guiding curve,horizontal straight generatrix and type of plough surface were known by analyzing the plough surface.The resistance force,plowing specific resitance and power consumption of modified front plow were only 35%~50% of counterpart of the original front plow,reducing more than 50% by conducting high speed digital soil bin test.The field test showed that furrow ditched by modified front plow was clean and flat.(4)The resistance charcter experiment of both front and rear ditching plow for rapeseed planter were conducted.The resistance force and power consumption of front ditching plow were both 2.3 times larger than counterpart of rear ditching plow,which was 70.3% of counterpart of the whole ditching system by conducting the high speed digital soil bin test and selecting the plow operation depth,plow operation width and soil strength as the experiment factors.Operation depth was the most important factor to affect the resistance force of the ditching system,whose important percentage value was 63.29%,and operation width and forward speed had almost the same importance,whose important percentage values were 44.73% and 46.52%,respectively by establishing the resgression model.Operation depth,operation width and soil strength all had a positive correlation with all experimental indexes.The operation quality satisfied the agronomic requirement of rapeseed planting when the front and rear plow worked cooperatively by field contrast test.(5)The optimization experiment of plough surface for rapeseed planter was conducted.The experiment selecting structural parameters and operation speed as the factors was conduced by establishing the EDEM simulation model and the result showed that the initial angle of plow share,length of guiding curve,initial angle of horizontal straight generatrix and maximum angle of horizontal straight generatrix had a significant influence on resistance force of plow.During the stage of low operation speed,the resistance force of plow increased linearly while during the stage of hight operation speed,the resistance force of plow increased exponentially.The optimal values of initial angle of plow share,length of guiding curve,initial angle of horizontal straight generatrix and maximum angle of horizontal straight generatrix were 15°,190 mm,35°,40°,respectively when the value of resistance force of plow was minimum by establishing optimal mathematical model about plough structural parameters.The models of optimal front plows and rear plows were printed by 3D printer and the prototypes of the plow were manufactured.The contrast field test was conducted and the result showed that the quantity of soil block in the furrow ditched by optimal plows decreased,reducing 62.87% compared with that ditched by the original plows and the furrow was cleaner and more stable.(6)The structure of ditching and rotary device of rapeseed planter was modified and corresponding field test was conducted.The locations blocking soil to be got out when rapeseed planter was working were front plow area,rear plow area and the middle area of rotary device by analyzing the operation situation large quantity of rice straw and clay soil existing.The field experiment about power consumption of rapeseed planter was conducted and the result showed that the ditching device olny consumed 24.13%~36.54% enegy of that consumed by rotary device.The structures blocking the soil easily were modified and the rotary blades consuming the enegy most were rearranged.By conducting field test,the locations easy to block the soil when rapeseed palnter was working were disappeared and the soil could move fluently.The value of power consumption of modified rotary device was reduced 14.13%~18.04% while there was no significant influence on the rapeseed growing.Innovation Point 1: A plow surface rolling the soil blocks and compacting the furrow shape at the same time was designed and the optimal structural parameters values of plow when the resistance force was minimum were obtained by establishing EDEM simulation model.Innovation Point 2: The cone resistance force-displacement curves were obtained by standard cone penetrating into the soil model.The prediction model of soil physical properties was obtained and the values of soil physical properties were acquired based on response surface.