Tool-straw-paddy soil coupling model of mechanical rotary-tillage process based on DEM-FEM

The working conditions involving rotary-tillage processes in the paddy fields are complex and dynamic, and certain parameters are difficult to measure in real-time. Owing to the lack of applicable analytical methods, the interactions among knife rollers, wheat straw, and paddy soil are not well understood, which prevents improvements to the rotary tillage quality in paddy fields. A dynamics model of the tool-straw-soil coupling system was established in this work using finite and discrete element methods to analyze the paddy rotary-tillage process. Soil bin test is crucial for verifying the reliability of simulation models and the accuracy of simulation results, the reliability and accuracy of the numerical model were verified based on a soil tank test. The results indicate that in terms of blade roller torque, mud disturbance, and straw embedment rate, for a single group of knife rollers throughout the three soil bin tests, the average torque was 11.99 Nem, significantly lower than the 19.32 Nem obtained from previous studies. The mud disturbance rate was 71.09%, and the wheat-straw burial rate was 85.64%, wheat-straw burial rate is slightly better than 83% obtained from previous studies. The errors between the simulations and the soil tank test regarding the knife roller torque, mud disturbance, and wheat-straw burial rate were 0.75%, 2.21%, and 4.83%, respectively. The proposed numerical simulation method reflected the variations in physical and mechanical parameters during the paddy field rotary-tillage. The proposed approach provides an effective method for visualizing and analyzing the rotary-tillage interactions and mechanisms in complex paddy field working systems.