Determination of the coefficient of rolling friction of an irregularly shaped maize particle group using physical experiment and simulations

The coefficient of rolling friction is an important physical property of a maize particle. It is difficult to obtain the value of this coefficient because of the irregular shape of maize particles. This paper describes an approach that combines the discrete-element method （DEM） and a physical test to determine the coefficient of rolling friction of irregularly shaped maize particles. A novel test platform was used to obtain the maize particle＇s coefficient of restitution and the coefficient of static friction. EDEM software （DEM- Solutions, United Kingdom） was used to simulate the accumulation of maize particles on particles and on a zincified plate. The golden-section method was used to determine the range of the maize particle＇s coefficient of roiling friction. A single-factor test was used to determine the relationship between the maize particle＇s coefficient of rolling friction and their angle of repose. The results obtained from the EDEM simulation were compared with physical test results to determine the intergranular coefficient of rolling friction and the coefficient of roiling friction between maize particles and the zincified plate. Our study demonstrates that the angle of repose increases linearly with the coefficient of rolling friction of maize particles. The effect of the coefficient of rolling friction on the particle movement is studied. The physical verification test indicates that the obtained rolling friction of the maize particles is accurate. The findings of this paper provide a theoretical basis for maize-processing machine design and a discrete-element studv of the motion of maize particles inside such machines.

Determination of the coefficient of rolling friction of irregularly shaped maize particles by using discrete element method

The coefficient of rolling friction is a foundation parameter for conducting particles simulation,however,which of irregularly shaped maize seeds is difficult to measure.Furthermore,the coefficient of rolling friction between the simulation particles and the actual seeds is inconsistent due to the shaped difference of model and different position of gravity center.This paper use two methods to determinate the coefficient of rolling friction based on discrete element method(DEM)and physical experiments.Three types of maize models from five different shaped maize samples(including horse-tooth shape,spherical cone shape,spherical shape,oblate shape,irregular shape)were developed with the help of slice modeling and 3D modeling technology.Aluminum cylinder container is used to arrange the simulation experiments of angle of repose with taking the coefficient of rolling friction as independent variables and the simulation angle of repose as target values.After predicting detailed the coefficient of rolling friction(including horse-tooth shape,spherical cone shape,spherical shape,between horse-tooth shape and spherical cone shape,between horse-tooth shape and spherical shape,between spherical shape and spherical cone shape maize models),and forecasting a unified the coefficient of rolling friction among horse-tooth shape,spherical cone shape and spherical shape maize models,two types of materials(aluminum cylinder container and organic glass container)were used to validate the difference the angle of repose between the simulation maize models and actual maize seeds.Results show the relative error of the angle of repose between the maize models controlled by the coefficient of rolling friction through the detailed method and the actual maize seeds is 0.22%,0.33%in aluminum cylinder,organic glass container,respectively.The relative error of the angle of repose between the simulation maize models controlled by the coefficient of rolling friction through the united method and actual maize seeds is 2.47%,2.97%in aluminum cylinder,organic glass container,respectively.Although the difference of the angle of repose between two method is smaller,the detailed method is better.Moreover,From the accumulation process of the angle of repose we found that the difference on the contacts number between maize models and bottom plate,the change curve of the rotational kinetic energy,the potential energy of maize models controlled by the coefficient of rolling friction through the detailed and the united method are evidently.We can choose a better method to predict the coefficient of rolling friction of maize seeds according to the application situation and investigation objective of irregular maize seeds.The results can provide a theoretical basis for designing and optimizing the structure of the seed-metering machine with DEM.

Investigation of interaction effect between static and rolling friction of corn kernels on repose formation by DEM

The coefficient of static friction(SF),the coefficient of rolling friction(RF)for particles are two key parameters affecting the repose angle formation and flow characteristics.In this paper,the interaction effects of SF and RF on the formation process of corn repose angle was investigated by the discrete element method.Firstly,five shape kinds of corn models(horse tooth,spherical cone,spheroid,oblate,and irregular shape)were established.Secondly,aluminum cylinder and organic glass box were used to conduct the simulation experiments with taking SF and RF as independent factors and seeing the repose angle as dependent value.Based on simulation results the regression equations were established.Simulation results showed the relation between two factors and the rotational kinetic energy is not nonlinear,and SF does not significantly restrict the flow of corn models after increasing the flow direction,and the effect of SF on the contact number between corns and the bottom plate is remarkable,while the effect of RF on the contact number is not remarkable.Finally,the interaction effect of two factors on the repose angle was analyzed by variance analysis and results showed SF and RF all have a significant impact on the repose angle.Moreover,their interaction effect has an impact on the repose angle.