Design And Experiment Of Press Roller With Bionic Convex Structure

The press roller is a typical rolling component in agricultural machinery used to properly compact the soil.The materials of the traditional press roller are mostly stone,cast iron or steel.From a macro perspective,these smooth structures can adhere the soil easily when the press roller is working,even resulting in insufficient pressure.In addition,when the traditional press roller is working,some soil will be pushed into the front of press roller to form a wavy bulge,which causes a phenomenon called“dumping soil”.This phenomenon not only makes the compaction effect unsatisfactory,but also produces the excessive working resistance and even leads to crop yield reduction.Therefore,based on the problem of serious soil adhesion and the large working resistance of the traditional press roller,it is necessary to design a press roller that can reduce soil adhesion and working resistance,which is very important for agricultural production.Inspired by the non-smooth structures of soil animals which can reduce soil adhesion and resistance（convex shape,concave shape,rib shape,scale shape,etc）.Also,due to the similarity between the convex curved surface shape of the gray snail shell and the convex structure,this study is based on the idea of bionics and uses the gray snail shell as the bionic object.Combining the theoretical analysis with the experimental research to design the press roller with bionic convex structure.The main research of this paper are as follows:（1）Using the idea of bionics,the press roller with bionic convex structure is designed by changing the contact between the press roller and the soil.The shell of gray snail is used as bionic object.The shape of convex surface of the snail shell is extracted by reverse engineering technique and curve fitting.Combined with PLA materials,3D printing is used to shape the convex structure.The new material PLA with some excellent characteristics（impact adhesion resistance,water absorption,etc.）can achieve good reduction of adhesion and working resistance.And PLA is an environmentally friendly material that does not cause pollution.（2）Constructing a three-dimensional model of press roller with bionic convex structure used Creo Parametric software.Using EDEM discrete element simulation software to simulate the dynamic process of interaction between press roller with bionic convex structure and soil.Analyzing the variation law of working resistance and soil subsidence caused by the press roller.The software Design-Expert 8.0.6 is used to carry out the three-factor and five-level regression orthogonal rotation combination test.Obtaining the relationship and the mathematical regression model between experimental factors（Forward speed,counterweight,convex height of the pressroller）and experimental indicators（Working resistance,soil subsidence）.On this basis,the multi-objective optimization of the mathematical regression model is carried out.Finally the optimal motion parameters and structural parameters of the bionic convex structure press roller are obtained:the forward speed of press roller is 4.8km/h,the weight is 360 N and the height of the convex structure is 12 mm.（3）The soil bin comparison test of the press roller with bionic convex structure and traditional cylindrical press roller commonly used in the northeast region is carried out.The main purpose is to investigate the soil adhesion reduction performance of bionic press roller.The comparison test is carried out using the optimal combination of parameters obtained in the EDEM test:the convex height of the bionic press roller is 12 mm,the forward speed of soil tanker is set to4.8 km/h and the weight of the press roller is set to 360 N.And the tests are carried out at three different soil water rates,they are 20%,24% and 28%,respectively.The amount of adherent soil and soil bulk density are examined.The test results reflect that the soil bulk density after two kinds of press rollers are between 1.0～1.3 g·cm^-3,which can meet the growth requirements of corn seeds.Compared with the traditional press roller the bionic press roller is not easy to adhere the soil,and the rate of soil adhesion are about 20% at three different water contents.（4）The field comparison test of the press roller is carried out.The main purpose is to investigate its reduction of resistance.This test is carried out along the optimal solution of the bionic press roller in the EDEM test.The height of the convex of the bionic press roller is 12 mm,the forward speed of the tractor is set to 4.8 km/h,and the counterweight of the press roller is set to360 N.At the same time,the test indicators of working resistance,emergence rate and soil bulk density are investigated.The test results show that the bionic press roller can make the rate of corn seed emergence reach to 83.86%,which is 9.1% higher than the traditional press roller.The reduction of resistance is very obvious,and the reduction rate is 27.77%.The test results are consistent with the simulation test,thus verifying the rationality of the simulation test.The press roller with bionic convex structure can effectively reduce the working resistance and the soil adhesion,which can improve the quality of the repressing operation.This provides a technical reference for the design of the press roller.