| The mechanical parameters of maize particles are the basic data for the design and analysis of maize processing machinery.It is difficult to get the accurate value of coefficient of rolling friction of irregular maize particle directly through physical test,the accuracy of its parameters directly affects the authenticity and effectiveness of the analysis results.In this paper,numerical simulation combined with physical experiment is used to explore the effect of coefficient of rolling friction between different shaped maize particles and zincified steel plate on the distribution of contact force under particles pile in the process of free accumulation of particles.the main research work was as follows:The moisture content,density and shape dimension of Jilan 92 maize particles were determined.According to the shape of maize,maize particles can be divided into three categories: spherical,cone-shaped and rectangular maize particles.Coefficient of static friction and coefficient of restitution between particles,between particles and zincified steel plate were measured by using the agricultural test platform of contact parameter of particle material.The results show that the values of coefficient of static friction and coefficient of restitution between maize particles are less than the corresponding contact parameters between maize particles and zincified steel plate,of which the coefficient of static friction between the spherical maize particles is the smallest(its value is 0.251),and coefficient of restitution between the rectangular maize particles is the smallest(its value is 0.392).Regarding coefficient of rolling friction as the factor,angle of repose measured by physical accumulation test(obtained by image processing technology)as the index,based on the Fibonacci method,the simulation test of particle accumulation is carried out by EDEM.The coefficients of rolling friction between three shapes of particles,between the particles and the zincified steel plate are calibrated by reducing coefficient of rolling friction between the particles and the zincified steel plate and establishing the relation equation of coefficient of rolling friction and the repose angle.The result shows that the greater the degree of irregularity is,the bigger the intergranular coefficient of rolling friction is,the value of the intergranular coefficient of cone-shaped maize particles is the biggest(its value is 0.1035),and the accuracy of the calibration is verified by experimental comparison.On the basis of the above research,a single factor experiment was carried out to simulate the accumulation process of three shapes of maize particle mixture on zincified steel plate by using EDEM discrete element software.The effect of coefficient of rolling friction between three shapes of maize particle and zincified steel plate on contact force and distribution under particles pile is analyzed.The experimental results show that with the increase of the coefficient of rolling friction,the average value of the normal and tangential contact forces between particles and basement increases first,and then gradually tends to the fixed value(0.005 N,0.0015 N),the radii of ring of the strong contact force decreases approximately linearly,the percentage of the strong contact force between particles and basement are the same.Regarding radii of ring of the strong contact force and average values of normal and tangential contact forces between particles and basement as an indicator,the three-factor and five-level quadratic regression rotation design experiment was accomplished,and the data were processed by Design-Expert software,the experimental results were analyzed by response surface methodology.With the increase of coefficients of rolling friction between three shaped maize particles and zincified steel plate,the average values of normal and tangential contact forces between particles and basement are increased initially and then stabilized,and the radii of ring of the strong contact force are increased primitively and then decreased.This paper further improves the analysis of the mechanical properties of irregular shaped agricultural granular materials,and provides a theoretical reference for granary design and structural optimization. |
