Design and Simulation of a Garlic Seed Metering Mechanism

According to the agronomic requirements of garlic sowing, the garlic morphology is studied and a garlic seed metering mechanism with excellent seeding performance is designed. Based on this design, a new garlic seeding machine with an adjustable-size seeding device is developed to realize efficient single-seed metering and seeding of different varieties of garlic. Further, the design scheme of the garlic seeder prototype is established, with the key components of the garlic seeding being designed on the basis of the garlic seeding mechanism. To achieve garlic single-seed metering for different varieties of garlic, the optimal adjustment size of the garlic seed metering device is determined through discrete element simulation analysis. A field experiment confirms the effectiveness of applying the proposed garlic planter to field sowing in terms of the metrics of missing seed and multiple seed rates. The results of the discrete element simulation test reveal that an adjustment size of 40 mm yields the best single-seed metering performance. At an operating speed of 15–35 rpm, the metering device can achieve more than an 80% qualification rate of single-seed metering, with a unit speed of 0.628–1.465 m/s. Thus, the developed garlic seeding device meets the requirements of precision sowing in China and can effectively realize the mechanized planting of garlic.

Simulation analysis and experiment of sampling process of wheel brush sampler based on discrete element method

In order to study the brush sweep sampling process through simulation analysis, the structure of the asteroid sampler is simplified on the basis of retaining the wheel brush. Soybean particles are selected as the verification sampling particles, and the physical and contact parameters of calibrated soybean particles are applied to the discrete element simulation software EDEM and the relationship between the sampling wheel brush speed and torque is analysed. At the same time, a set of wheel brush asteroid sampler ground torque test system is built to verify the accuracy of the discrete element simulation results. The results show that the driving torque of the sampling wheel brush is mutational in the process of sampling, and the faster the rotation speed of the sampling wheel brush, the more the mass of the collected particles, and the greater the driving torque required for the sampling wheel brush. This research provides a method basis for the structure selection and parameter optimization design of the asteroid sampler.

Discrete Element Simulation Analysis of Damage and Failure of Hydrate-Bearing Sediments

It is of great significance to study the damage and failure law of hydrate-bearing sediments for for exploration and development, as well as for warning secondary disasters such as tsunami and earthquake. The discrete element modeling and simulation method has the advantages of low cost, strong repeatability and accurate response to the microstructure of samples, therefore , the discrete element method is used to simulate and analyze the damage and failure law of hydrate-bearing sediments in this paper. First, a triaxial undrained shear teat model of hydrate-bearing sediments is established. by discrete element simulation software; Then, the effects of different influencing factors on the fracture characteristics of hydrate hydrate-bearing sediments is studied; Finally, the effects of different factors on the initiation stress and damage stress of hydrate sediments are analyzed, and the damage law of hydrate-bearing sediments is obtained. The results show that: (1) The cementation of hydrate particles is greater than its bearing effect, thus the lithology of sediments changes from loose sand body to brittle rock with the increase of hydrate saturation, resulting in the corresponding change of fracture characteristics from loose sand body failure to brittle rock failure. (2) With the increase of hydrate saturation, the initiation stress of sediment shows a step-by-step increase law, and the damage stress is positively correlated with the shear modulus. (3) The heterogeneity of hydrate distribution is closely related to the failure mode of sediments. With the increase of hydrate distribution heterogeneity, the initiation stress displays an increase-decrease-increase pattern while the damage stress shows a law of increasing and then decreasing, which has the high sensitivity to heterogeneity of hydrate distribution. The research results have certain theoretical reference significance for the exploitation practice of natural gas hydrate.

Discrete Element Simulation Based on Elastic–Plastic Damping Model of Corn Kernel–Cob Bonding Force for Rotation Speed Optimization of Threshing Component

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%.