Friction coefficient calibration of corn stalk particle mixtures using Plackett-Burman design and response surface methodology

Abstract

The accuracy of the particle parameter settings directly affects the reliability of the simulation results. The discrete element method used a repose angle test to address incorrect particle parameter settings when throwing straw particles thrown by a chaff cutter. The tests calibrated the static and rolling friction coefficients using the repose angle of a mixture of maize stalk internodal tissue, pith, and nodal tissue particles as response indicators. Physical tests measured particle materiality parameters and contact parameters to provide data for the simulation tests. A Plackett-Burman design was performed to test the significance of the parameters to be calibrated. The results show that the static friction coefficient of Rind-Node, the rolling friction coefficient of Rind-Rind, the rolling friction coefficient of Pith-Pith, and the rolling friction coefficient of Pith-Iron have a significant effect on the repose angle. The purpose of the steepest ascent test is to narrow down the optimization range of the parameters. The central composite design was used to determine the DEM parameters' levels and quantify their effects. The central composite design test modeled a second-order polynomial regression equation for the repose angle and significance parameters. The physical test values were used as the target values for the optimization solution to obtain a calibrated and better combination of simulation parameters. The two-sample heteroskedasticity t-test showed no significant difference between the simulated and experimental values. The maximum relative error was 1.75%, the mean relative error was only 0.29%, verifying the reliability and authenticity of the simulation test. These parameters provide a basis for future work, such as the design of a corn stalk processing machine and the discrete-element study on the motion of corn stalk particles inside such machines.