A DEM-based general modeling method and experimental verification for wheat plants in the mature period

Simulation of the wheat harvesting process using the discrete element method is of significant importance in optimizing the components of wheat harvesting machinery. Establishing a discrete element model that can accurately reflect the biomechanical properties of wheat plants is a crucial foundation for simulating harvesting operations. To address the current issues in the discrete element model (DEM) of wheat plants, a general modeling method for wheat plants was developed in this study. Firstly, the shape and size of 10 representative varieties of wheat plants in the mature period from different regions in mainland China to establish the common correlations between the shape and size of wheat plants. On this basis, a geometrical model of wheat plants was built using the particle arrangement method, and the coordinates of the component particles were solved for. Then, the contact mechanical parameters were measured and calibrated through various tests, including the slope test, single-pendulum test, drop test and stacking angle test. Moreover, the parallel bonding mechanical parameters of wheat plants were measured and analyzed by tensile, compression and shear tests. On this basis, the mechanical model of wheat plants was established based on the Hertz-Mindlin contact model and the parallel bonding model (PBM). The geometrical model together with the mechanical model enabled the construction of a DEM-based model of wheat plants with flexible characteristics. Based on the above work, the models that were proposed in this paper for three varieties of wheat were validated by comparing the experimental data and simulation results in terms of the plant stacking test, vibration screening test and impact threshing test. The results demonstrated that the simulation results for all three varieties were similar to the experimental results, which showed the feasibility and effectiveness of the general modeling method proposed in this paper for wheat plants in the mature period. The results of this study lay a foundation for the analysis of the wheat harvest process by the discrete element method.