Parameter calibration of coconut bran substrate simulation model based on discrete element and response surface methodology

In order to improve the accuracy of the parameters used in discrete element simulation study of coconut bran, physical and simulation experiments were combined to calibrate discrete element simulation parameters of the species. First, the intrinsic parameters and actual stacking angle of coconut bran were measured through physical tests. Next, the simulated stacking angle was used as the response value, Plackett-Burman test was designed with Design-Expert software, and the parameters that had a significant impact on the stacking angle were identified and selected. The results of the screening test show that the static friction coefficient of coconut bran-coconut bran, the rolling friction coefficient of coconut bran-coconut bran and the static friction coefficient of coconut bran-steel plate have significant effects on the stacking angle. The relative error of the stacking angle was taken as the evaluation index, the steepest climbing test was performed on the three significant parameters, the value range of the significance parameter was optimized, and Box-Behnken test was adopted to establish the quadratic regression model between the stacking angle and significance parameters based on response surface methodology (RSM). the stacking angle of 20.08° measured by the physical experiment was taken as the target value in the model, and the regression equation was optimized to obtain the optimal combination of parameters: 0.48 for the static friction coefficient of coconut bran-coconut bran, 0.28 for the rolling friction coefficient of coconut bran-coconut bran, and 0.39 for the static friction coefficient of coconut bran-steel plate. Finally, the verification tests on the stacking angle and fluidity of coconut bran were carried out, and the results show the average relative errors of the two tests are small, which verify the reliability of the calibration results and research methods of coconut bran simulation parameters. The research results show the calibrated parameters can provide references for the selection of coconut bran discrete element simulation parameters and the design and optimization of related equipment.