A calibration method for contact parameters of agricultural particle mixtures inspired by the Brazil nut effect (BNE): The case of tiger nut tuber-stem-soil mixture

The lack of calibration methods for the contact parameters of agricultural particle mixtures limits the numerical simulation optimization of agricultural equipment. In this study, a novel method for calibrating contact parameters in agricultural particle mixtures inspired by the Brazil nut effect was proposed. The effectiveness of the proposed method was evaluated using a case study of a tiger nut tuber-stem-soil mixture. The intrinsic and contact parameters of monomaterials were first determined by conventional tests to provide data for vibration simulation tests. Vibration segregation tests were then performed on binary mixtures. The determination coefficient R2 between the physical and simulation data of the target particle volume concentration in the mixture was used as a response indicator. The second-order response surface regression model between the contact parameters and R2 was fitted by response surface methodology (RSM). The significance of the effect of the contact parameters on the indicator was quantified, and the optimal values of each parameter were determined. Finally, the applicability and accuracy of the calibrated parameters were verified using the self-flow sieving test. The results showed that the distribution of the mixture on the sieving surface and in the receiving box obtained from the calibrated test best matched the physical test results; at this time, the maximum relative errors of the physical and simulated values of the mass percentages of the tuber, stem and soil in the bin were 8.2%, 7.6%, and 6.5%, respectively, indicating that the calibrated parameters have good applicability and accuracy. The calibration test method can guide the calibration of contact parameters for other agricultural particle mixtures.