Calibration Of Contact Parameters Of Media For Discrete Element Simulation

Discrete Element Method(DEM)can be effectively used to analyze mass finishing processes.However,as the key processing media,their contact parameters of the media have a great impact on the analysis results.Different media have different surface quality,so it is need to be calibrated according to the specific conditions.Parameters of media lacked standardized and effective calibration method.Taking the repose angle of the media as a standard,this paper studied on calibration method for contact parameters of media systematically by the image processing and discrete element method.Thus,a media contact parameters calibration and prediction method was obtained,which laid a good foundation for the optimization design of mass finishing process parameter.The main research of paper is as follows:1.To reveal the necessity of media parameters calibration and the influences of media parameters on the mass finishing,based on the EDEM,nine media parameters were selected and analyzed with the mean velocity,the mean energy and the mean contact force of the media in manufacturing as evaluation indexes.The most significant parameters which can influence the 3 evaluation indexes during finishing process were filtered out,and the relationships between the significant parameters and the 3 evaluation indexes in the machining process were evaluated,and corresponding equations were derived.2.Taking the repose angle of the media as a standard,the feasibility of the calibration methods were analyzed and contrasted by using "emptying","pouring","filling" and "rolling" method to calibrate the contact parameters of media.The results show that: "filling" method is the most simple and effective method to calibrate the contact parameters of media.3.Aim at current existent problems and defects in use traditional contact measuring method to measure the repose angle of the media,an image analysis method is proposed.In order to use image analysis method to measure the repose angle of the media,the process of measurement was studied in detail,and the influence of image distortion in the process of measurement was reduced.This study laid an important foundation for next implement automation of repose angle measurement and media contact parameters calibration.4.In this study,the repose angle of the spherical media was obtained from “filling” experiment and image analysis method,and taken as a standard for determining the contact parameters used in the DEM simulation.Three contact parameters in the simulation model,which have a significant effect on the repose angle of the spherical media,were screened out by Plackett-Burman test.The relationship between the main contact parameters and the repose angle of the spherical media was obtained by the steepest ascent test and Box-Behnken test,and the main contact parameters are determined.The obtained results were then validated by DEM simulation,and the relative error between the simulation results and the experiment results was 0.56%,which shows that it is effective method to calibrate the contact parameters of the spherical media.In this paper,based on the discrete element method,the parameter calibration method of media is systematically studied.Firstly the influences of media parameters on the centrifugal barrel finishing and the necessity of media parameters calibration were analyzed,then the suitable calibration method of media contact parameters calibration was selected and image analysis method was used into the media repose angle measurement.Finally,the method was used to calibrate the spherical media contact parameters to verify the correctness of this method,which improve the accuracy of using the discrete element method to study the process of mass finishing,and promotes the development of mass finishing technology.