| Hilly region in Northeast China,about 0.788 million hm2,nearly 38.5% of the total area,includes the southwest of Heilongjiang Province,the eastern of Jilin Province and the eastern and western eastern of Liaoning Province.Hilly region in Northeast China are located in Mollisols(called Black soils)region,which is one of the three largest Mollisol areas in the world.Black soils are fertile and productive;thus,they are of major agricultural importance in China,while the agricultural mechanization level in hilly region is relatively weak.In recent years,researchers focused on agricultural machinery technology in plain region,while relatively little research had been done in hilly region.Plain sowing machines were usually used directly for hilly region tillage,which could improve the efficiency and quality of sowing,however,there are still some problems,such as serious soil adhesion,large traction resistance,inhomogeneous suppression and insufficient compressive strength.Taking the above-mentioned problems as the breakthrough point,this research takes the suppression technology of planter in hilly region as the research direction to study the mechanism of the suppression technology in hilly region,the operation performance of the wheel in hilly region by numerical simulation method,the basic theory and operation law of structural design and design the suppression device suitable for hilly region,so as to meet the requirements of the suppression operation in hilly region.The main research contents are as follows:(1)Research on the mechanism of press technology in hilly regionTaking the problems of lateral inhomogeneity,serious soil adhesion and large traction resistance as the breakthrough point,the movement process of unidirectional and bidirectional profiling is analyzed to determine the feasibility of profiling in hilly region;the basic conditions and optimal conditions of soil desorption are obtained by studying the mechanism of soil desorption;and the quasi-static state of wheel and soil based on hilly terrain is established.The main factors and rules affecting traction resistance are obtained by the action model,and the influence of speed on traction resistance and operation quality under the dynamic action m odel is also studied.(2)Numerical simulation of press wheel and soil in hilly regionIn the case of press operations in the hilly region of Northeast China,the soil moisture content of different topography and topography varies greatly.To achieve bett er press effect,the corresponding load and forward speed need to be matched.Taking the common rigid press wheel in hilly region as the research object,a three-dimensional simulation model of rigid press wheel and soil is constructed based on SPH algorithm in LS-DYNA software to simulate the dynamic process of interaction between rigid press wheel and soil.Study the dynamic process of the interaction between press wheel and the soil between press operation parameters and the effect of the repressing operation.The numerical simulation method is combined with the central surface composite response test scheme to carry out simulation experiment.The variance test is carried out on the simulation test results to study the influence of test factors on the per formance of the press operation.The simulation experiment obtain the mathematical regression model of soil water content,load,forward speed and soil subsidence,and traction resistance.On this basis,the ant colony algorithm in R language is used to optimize the mathematical regression model and obtain the Pareto optimal solution set.The soil trough test is carried out to verify the optimal solution,verify the reliability of the optimization results,and verify the feasibility of the simulation.This study provides the theory and basis for the research of planter and supporting technology in hilly region.(3)Research on press in mechanical reducing adhesion and resistanceAiming at the problems such as serious soil adhesion,large traction resistance during the press operation,a press device in mechanical type reducing adhesion and resistance was designed according to the method of terrain machines reducing adhesion and resistance.In order to study the working performance of mechanical reducing adhesion and resistance press device,the spring stiffness coefficient,the advancing speed and the scraping angle are taken as the test factors,and the traction resistance and soil adhesion were used as test indicators to conduct si ngle factor test in the indoor soil trough.Orthogonal test L9(34),to investigate the influence of test factors on the working performance of the repressing device.The results of single factor test show that the spring stiffness and traction resistance are approximately linear.The spring stiffness and the test index are negatively correlated.The working speed is positively correlated with the test index.The scraping angle and the test index are approximately parabolic.The results of orthogonal test sh ow that the primary and secondary order of each factor affects the index: spring stiffness coefficient,scraping angle and advancing speed;optimal horizontal combination: spring stiffness coefficient 40 N/m,scraping angle 30 o,forward speed 7 km/h.The verification test was carried out at the optimal level: the traction resistance was 39.6 N and the soil adhesion was 43.24 g.(4)Research on bidirectional press device in hilly regionAiming at the problems of uneven press and insufficient repressive stre ngth during operation in hilly regions,this paper design a repressing device that can realize bidirectional profiling and adjustable press strength,and focuses on the contour adjustment mechanism of the device.The design of the suppression strength adjustment mechanism.In order to study the viscous and drag reduction performance of the two-way profiled repressing device,the rigid press wheel was taken as the research object,and the working speed and spring deformation were taken as the test factors,and the traction resistance and the viscosity reduction rate were used as test indicators to respond in the indoor soil trough.The surface test studies the influence of test factors on the test indicators and obtains the optimal horizontal combination.In order to study the profiling performance of the two-way profiling device,a comparative test iss carried out in the field to prove that the contouring device is better to ensure the uniformity of the pressure.In order to study the field performance test of the two-way profile remanufacturing device,the reinforcement wheel type,the press strength and the working speed were used as the test factors,and the traction resistance and the root canal ratio were used as the test indicators.The L9(34)orthogonal test is carried out to investigate the type of the reinforcement wheel.The influence of the suppression strength and working speed on the working performance of the repressing device,the optimal combination: the rubber wheel and spring deformation amount is 20 mm,and the working speed is 1 m/s.At this time,the traction resistance is 22.3 N,and the root-to-crown ratio is 0.271.(5)Research on the effects of different repression treatments on maize characteristicsThe effects of different press treatments on physiological characteristics of maize were studied by taking the type of press wheel and operation speed as experimental factors.It was found that soil moisture content decreased after sowing,some of which supplied seed germination and seedling growth,and the other part water evaporated normally.Compared with rubber and squirrel cage press,plane press wheel(rigid press)surface soil was more compact,effectively controlled water evaporation and temperature exchange,and the corresponding so il moisture content and soil temperature were the highest.The smaller the speed is,the more compact the surface soil is,the smaller the evaporation of water and the better the heat preservation,but the effect of operation speed on soil water content is not different.Because the rigid press wheel and operation speed of 3 km/h had the highest soil water content and soil temperature,enough water and appropriate temperature were guaranteed to accelerate the germination process of maize seeds,the average emergence time of this combination was the shortest,then the later stage.The corresponding seedling growth potential is the same,and the corresponding plant height consistency is the highest.The average seedling emergence time corresponding to 3 km/h a nd 5 km/h operation speed was almost the same,and the seedling emergence rate corresponding to the combination of 5 km/h operation speed and planar compressor wheel is the highest.Considering that the operation speed has no difference on soil physical properties and the efficiency of sowing operation,the sowing operation speed should be properly increased.Therefore,the combination of planar press wheel and operation speed of 5 km/h was the best combination. |
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