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

Abstract

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.

Applications of Discrete Element Method in the Research of Agricultural Machinery: A Review

“…The repose angle test was widely used to determine the static and rolling friction coefficient between crop seeds, and its calibration process was similar with the soil parameters. As listed in Table 1, the static and rolling friction coefficients of many kinds of crop seed have been calibrated [78,[82][83][84][85][86][87][88][89][90][91][92]. The static and rolling friction coefficients between crop seeds and contact materials were usually determined with a slope sliding method or self-made coefficient determining apparatus [64]; collision coefficients of restitution were calibrated with seed dropping tests and collision tests [74,75].…”

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

“…x direction y direction 1 0. Based on the simulation results from Table 4, two binary quadratic regression equations between two factors and the repose angle were established, respectively, as shown in Equations ( 6) and (7). When the actual repose angles taken as y 1 and y 2 were substituted into Equations ( 6) and ( 7), respectively, the coefficient of static friction x 1 , and the coefficient of rolling friction x 2 were calculated.…”

“…The non-spherical ballast model gives a more realistic angle of repose behaviors compared to simply particle models [6] . On the other hand, the coefficient of static friction, rolling friction also are two key parameters affecting the formation of repose angle, flow characteristics [7] .…”

“…Based on the results of the previous study [7] , the interaction effects of the inter-corns coefficient of static and rolling frictions on the repose angle of corn kernels were investigated with DEM based on binary quadratic mathematical regression models. In addition, the effect of them during the formation process of corn models on the rotational kinetic energy, the contact number are studied in detail.…”

Contact parameter analysis and calibration in discrete element simulation of rice straw

“…In recent years, the simulation analysis technology of discrete element method (DEM) receives great attention in the design and improvement of agricultural machinery parts. DEM can accurately analyze the movement law of agricultural materials [8,9] , provide a microscopic visual analysis of rice straw particles, dynamic meso-contact behavior between rice straw and agricultural machinery parts, thereby providing technical parameters for trial production of physical prototypes and avoiding structural problems before trial production. However, in discrete element simulation, contact parameters (collision recovery coefficient, static friction coefficient, and rolling friction coefficient) of rice straw-rice straw and rice straw-agricultural machinery parts cannot be directly determined by physical tests.…”