Investigation Of Physical And Mechanical Properties And Modelling Method For Soybean Grains

Determined the parameters of Hertz Minderlin model and established geometric model of soybean grains are required for simulating the process of harvesting,transporting and processing of soybean grains by using the Discrete Element Method(DEM).Among them,the parameters of Hertz Minderlin model are mainly tested by the physical and mechanical properties of soybean grains.However,the test method and research on the physical and mechanical properties of soybean grains are not systematic and in-depth,and it is lack of relevant basis to simplify the shape of soybean grains into an ellipsoid to establish geometric model of soybean grains,and there is no discussion of the applicable situation and scope of the model.In this paper,these issues will be studied in depth,the main work and conclusions are as follows.First of all,three varieties of soybean grains are selected as the research object in this paper.The physical and mechanical properties of soybean seeds in 5 kinds of moisture content are tested and analyzed to study the effects of moisture content on the physical and mechanical properties.It is found that the three axial dimensions(length,width,thickness)approximately comply with the normal distribution.There is a certain functional relation between the three axial dimensions,and the three axial dimensions increase linearly with increasing moisture content.The parameters of the physical,mechanical and interaction properties have different variation laws along with the variation of moisture content.Secondly,four varieties of soybean grains are selected to verify the degree of approximation between soybean grains and ellipsoid.It is found that the shape of soybean grains is approximate to ellipsoid,and ellipsoid can be used to describe the geometric characteristics of soybean grains group realistically.Three kinds of single soybean grains modeling methods are proposed in this paper.To established geometric model of soybean grains group realistically,a template of soybean grains is established,taking the average of the width of the tested varieties of soybean grains as the width of the template.The width can be randomly generated in accordance with the normal distribution,and other dimensions are generated according to the relationship with the width,so that the dimension and distribution of the generated grain groups are close to the actual situation.Then,the modeling of template is carried out by the modeling method of single soybean grains to complete the modeling of the whole soybean grains group.Finally,two varieties of soybean grains are selected for measurement of repose angle and penetration rate,and the simulation results are compared with the experimental results to investigating the feasibility and effectiveness of the soybean grain modeling method and the filling scheme of soybean grains with different size ratio in the establishment of geometric model.In addition,the sensitivity of the parameters is analyzed to study the effect of different parameters in simulation.It is found that the 5-spheres soybean grains modeling methods can be applied to the geometric modeling of soybean grains.In the simulation,the static friction coefficient and the rolling friction coefficient have great influence on the simulation results.The shear modulus and the collision coefficient have little effect on the simulation results.