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Effect of calibration experiments on the micro-parameters of wheat required in discrete element simulations
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: 2017 ASABE Annual International Meeting 1701337.(doi:10.13031/aim.201701337)
Authors: Fanyi Liu, Jun Chen
Keywords: cylinder-lifting test, discrete element method, dynamic angle of repose, parameters study, rotating drum test, static angle of repose.
Abstract. Angles of repose measured in various calibration experiments were widely used to determine the micro-parameters of agricultural bulk materials required in discrete element method. However, the effect of these calibration experiments on the calibrated micro-parameters is still uncertain. In this study, difference among the calibrated micro-parameters of wheat was studied qualitatively and quantitatively by two representative tests, namely the cylinder-lifting test (static angle of repose) and the rotating drum test (dynamic angle of repose). The Plackett-Burman design was firstly simulated to screen the micro-parameters which significantly affected the angles of repose. Based on the simulation results of Box-Behnken design, regression models for the static and dynamic angles of repose with the screened micro-parameters were developed, respectively. The qualitatively comparison was conducted by finding a set of micro-parameters which could simultaneously made the simulated static and dynamic angles of repose matching well with the experimental ones. However, no such set of micro-parameters was found, showing that the two calibration tests will lead to different sets of micro-parameters. For quantitatively comparison, two sets of micro-parameters were respectively calibrated and validated by the two tests, from which large difference was found. Specifically, the wheat-wheat coefficient of static friction, the wheat-acrylic coefficient of static friction and the wheat-wheat coefficient of rolling friction were calibrated as 0.40, 0.42 and 0.092 for the static test, 35%~100% higher than the dynamic test (0.20, 0.31 and 0.048). Both the qualitative and quantitative studies indicate that the two calibration experiments have an effect on the calibrated micro-parameters of wheat.
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