This study addresses the high breakage rates in the traditional mechanical processing of maize kernels. This paper examines force transfer and consumption within longitudinal and transverse force chain networks by integrating high-speed low-flow and low-speed high-flow methodologies. A mathematical model was developed, incorporating the concept of contact force. Using factors such as airflow impact angle, direction, and regions of maize ears as test variables, three-dimensional force values and threshing quantities were analyzed as key performance indicators. The investigation explored the relationship between three-dimensional forces, destructive forces, and these test factors while examining changes in primary impact forces. High-speed photography was employed to validate the established threshing rules and trajectories. Results indicated that contact forces among different regions of a maize ear were approximately equal. Under specified conditions, transverse threshing was more efficient than longitudinal threshing. The magnitude of the three-dimensional forces followed the order of Z-direction > Y-direction > X-direction, indicating that the predominant impact occurs primarily along the Z-axis. For the force values in each direction and region, the large sections exhibited the highest forces, followed by the middle sections, while the small sections displayed the lowest overall forces. Additionally, longitudinal three-dimensional force values exceeded those measured transversely. The destructive force resulting from longitudinal chain network fractures was greater than that from transverse chain network fractures. Furthermore, within each region, the destructive force was inversely proportional to the number of threshing rows. In contrast, across different regions, this value was positively correlated with the number of threshing rows. The rate of change in force values within each region directly correlated with the impact angle. High-speed photography revealed that the transverse threshing process follows a spiral trajectory, whereas the longitudinal threshing trajectory aligns with the axial direction. The movement trajectories of maize kernels are all similar to parabolic movements. This study fills a gap in the study of airflow threshing for high water-content maize.

To make up for the gap in the research on high water content maize threshing by airflow, this study took high-speed, low flow, low-speed high flow airflow, and high water content maize ear as the research basis. The variation of air flow impacted threshing in numerical simulation, and the variation process of smoke visualization in the threshing area was compared. Taking the maize ear direction, the angle between the maize ear and the air pipe, the diameter of the air pipe, and the flow rate of the air compressor as factors, single-factor and quadratic regression orthogonal rotation combination tests were carried out, and the parameters were optimized. Finally, high-speed photography was used to shoot the maize kernels’ shelling process, and movement rules were analyzed from both the front and side views. The results showed that the velocity changes of each section under the numerical simulation are consistent with the flow state changes of smoke. The velocity reached its maximum on the circumference of the maize ear surface and presented a symmetrical distribution. Due to the velocity gradient and pressure gradient difference, the high-speed airflow would entrain the phenomena of the low-speed airflow. When the transverse maize ear, the angle between the maize and the airflow tube) was 45°, the diameter of the airflow tube was 7 mm, the flow rate of the airflow tube was 33 m/s, the loose amount was 10 pieces, the threshed amount was 15 pieces, and the damage rate was below 3%. Through high-speed photography, it was found that the cyclic force circle was destroyed after the maize kernel fell off, the motion of the removed maize kernel was similar to the oblique throwing motion, and the threshing process was carried out in the unit of “arrangement unit”. The threshing process followed the “arrangement law”, and the threshing track was “spiral”. The results of this research can provide ideas for the mechanical design and development of high-moisture-content maize threshing by air.

Since the fracture property of corn stalk determines the difficulty for corn to fall off, it is of great significance to study the fracture law of the corn stalk with high water content and explore the corn threshing method without causing great damage. Taking two varieties of corn as the research object, this study carried out single and multi-angle corn stalk fracture tests to explore the changes in the linkage between stalk and corn kernel at different positions as well as under different application modes and angles. The results showed that the force required for radial stretching was the greatest. Moreover, the fracture mechanics model of corn stalk was established to measure the fracture toughness of corn stalk. The peak value of critical load P_Q load displacement curve (F_MAX) was indicated. Based on the fractal theory, the fractal characteristics of the fracture surface of the stalk at different positions of the ear were analyzed, and the fractal dimension was calculated using the islet method. The findings indicated that the larger the fractal dimension of the fracture surface on the corn stalk, the more energy consumed in the fracture of corn stalk. These findings can be further utilized to explore the performance of corn kernel and reveal the fracture rule of corn kernel and stalk to identify the optimal form of force to make corn kernels fall off the corn cob and provide the theoretical basis for reducing the loss caused in the falling process of corn kernel.