Physical Properties and Experimental Study of Cotton Stalks from Typical Arid Regions of Southern Xinjiang Based on DEM

Using the discrete element method to simulate the interaction between cotton stalks and machinery is an effective approach for analyzing the cotton stalk defibration mechanism and optimizing the structural parameters of cotton stalk defibration equipment. To further improve the accuracy of studies on the interaction between cotton stalk defibration devices and cotton stalks, cotton stalks from typical arid regions in southern Xinjiang were selected as the research object, and a discrete element parameter calibration study was conducted based on the discrete element method. Considering the differences in cotton stalk diameters, two discrete element models of cotton stalks with diameters of 8.5 mm and 10.5 mm were established. Plackett–Burman screening tests and Box–Behnken tests were employed to calibrate and optimize the discrete element contact parameters for cotton stalk models with different diameters. Optimization was carried out using the load responses obtained from mechanical tests of cotton stalks as the target values, and the optimal parameter combinations of the cotton stalk discrete element models were determined. Finally, the calibrated parameters were validated through tensile tests, uniaxial compression tests, and bending tests of cotton stalks. The simulation results show that the relative errors between the simulated and measured maximum loads for the 8.5 mm- and 10.5 mm-diameter cotton stalk models were 1.21% and 0.08%, respectively, indicating good agreement. These results verify the accuracy and reliability of the established cotton stalk discrete element models and provide data support and a theoretical basis for numerical simulation of the defibration process of cotton stalks with different diameters and for the structural optimization of cotton stalk defibration devices.