Abstract
Current corn kernel-cob bonding mechanics models (LSD models) uniformly consider the bonding force changes during the maize threshing operation as an elastic change, resulting in computational errors of up to 10% or more in discrete element simulations. Due to the inability to perform high-precision discrete element simulation of the mechanics characteristics during the corn threshing operation, the core operating parameters of the corn thresher (rotation speed of the threshing component) rely mainly on empirical settings, resulting in a consistent difficulty in exceeding 85% of the corn ear threshing rate. In this paper, by testing the mechanics characteristics of corn kernels, the bonding force is found to have both elastic and plastic changes during the threshing process. An elastic–plastic (EP) damping model of the corn kernel–cob bonding force was established by introducing a bonding restitution coefficient e to achieve an integrated consideration of the two changes. By testing the relationship between the properties of the corn ear itself and the model parameters, the pattern of the effect of the corn ear moisture content and the loading direction of the ear by force on the EP model parameters was found. By establishing a model of the relationship between the corn cob’s own properties and the model parameters, the EP model parameter values can be determined by simply determining the moisture content of the ear. In this paper, the EP model was established and the high-precision simulation and analysis of the process of bonding force variation between corn kernel and cob is realized on the self-developed AgriDEM software. At the meantime, the optimal values of the threshing component rotation speed under different conditions of moisture content of corn ear were obtained by establishing an optimization model of threshing component rotation speed. The test results showed that the corn ear threshing rate could reach more than 92.40% after adopting the optimized speed value of the threshing component in this paper. Meanwhile, the test results showed that the discrete element simulation results based on the EP model did not significantly differ from the measured results of the thresher. Compared with the most widely used LSD model, the EP model can reduce the computational error by 3.35% to 6.05%.
Highlights
The higher the corn ear threshing rate of a corn thresher, the lower the losses in corn production [1,2]
Compared with the linear elastic damping (LSD) model, the EP model established in this paper can improve the calculation accuracy by 3.35–6.05%, and the advantage becomes more obvious with the increase in moisture content
An elastic–plastic (EP)_ damping model of the corn kernel–cob bonding force is established by introducing the bonding restitution coefficient e, and the residual displacement phenomenon of the kernel can be simulated in the discrete element simulation
Summary
The higher the corn ear threshing rate of a corn thresher, the lower the losses in corn production [1,2]. The high rate of corn ear threshing depends mainly on whether the rotation speed setting of the threshing component in the thresher is reasonable [5]. The corn thresher uses the rotation of the threshing components to repeatedly knead the kernels [6,7]. The magnitude and frequency of changes in the kernel-to-cob bonding force during threshing are influenced by the rotation speed of the threshing component [13,14]. Numerous studies have shown that the kernel-to-cob bonding force is influenced by the moisture content of the corn ear. The key to achieve the optimal setting of the threshing component rotation speed is to clarify the effect of the threshing component rotation speed on the bonding force between the kernel and the cob under different conditions of moisture content of the corn ear
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