Development of a FDEM model for cotton stalks based on biomechanical and structural properties

In the mechanised recovery process of drip irrigation tapes, the crossing of side branches and lodged cotton stalks (CS) are significant factors contributing to the increased breakage rate. Effectively cutting the cotton stalks is key to solving this issue. Constructing a multi-scale numerical model of cotton stalks is a breakthrough method for studying their fracture process. This study analyses the mechanical properties and structural composition of different sections of cotton stalk. Based on this, adopts a finite-discrete element method (FDEM) combined with zero-thickness cohesive elements to construct a numerical model of the cotton stalk, and the model's accuracy was validated through random sampling. The results indicate that the proportion of lignified tissues in the CS gradually decreases from the base to the top, and the load-bearing capacity of the CS shifts from strong compressive and shear resistance to greater ductility and tensile strength, while the compressive force values exhibit a decreasing trend with the presence of jump points, the average values of which are located at 14.5 % (base), 56.2 % (middle), and 29.3 % (top) of the CS length. The constructed composite model of the cotton stalk accurately replicates its mechanical properties, force transfer, and damage evolution processes. The Spearman correlation coefficients for the random sampling simulation and experimental validation of CS at different sections reached 0.9998 (base) and 0.9207 (top), respectively. This study offers a groundbreaking method for investigating CS damage mechanisms and can also offer technical guidance for the recovery of drip irrigation tapes under this irrigation management model.