Research Insight—Simulation analysis of the fracture process of high-moisture corn kernels

Recently, Professor Li Xinping's team from the College of Agricultural Equipment Engineering at Henan University of Science and Technology has made new progress in the study of the mechanism of corn shelling damage. The relevant research results have been published in the internationally renowned journal Applied Sciences (top journal in related area).

Corn, as a globally significant food and cash crop, relies on mechanized threshing as a critical step in achieving efficient production. However, the high grain damage rate during threshing has long hindered the sustainable development of the corn industry. Traditional mechanical threshing methods (such as impact, friction, and compression) are highly efficient but tend to significantly increase grain damage rates during threshing of high-moisture corn, leading to reduced seed viability and storage challenges. According to statistics, China's annual corn planting area is approximately 12.4935 million square kilometers. The massive production scale has created an urgent need for low-damage threshing technology. In particular, there are significant differences in tolerance to mechanical damage between seed corn and commercial corn. Optimizing threshing processes is of great significance for improving seed quality and enhancing the processing efficiency of commercial corn.

In recent years, various technical approaches have emerged in the field of low-damage corn husking: biomimetic husking equipment reduces impact force by simulating natural husking mechanisms; flexible husking methods utilize materials with variable stiffness to mitigate mechanical compression; and progress has also been made in the design of elastic structures and cone drum theory for high-moisture corn. However, existing research has primarily focused on optimizing and improving equipment structures, with limited systematic analysis of the connection mechanism between kernels and cob axes (particularly the mechanical properties of stalk fracture). The fiber connection strength and fracture patterns of high-moisture corn stalks remain unclear, hindering the further development and application of low-damage threshing theory.

This study focuses on the core issue of stalk breakage during corn husking, proposing a research framework that combines multi-dimensional experiments with simulation. The research team selected two corn varieties, “Boyun 88” and “Zhengdan 958,” using a texture analyzer to measure the triaxial fracture force parameters of the stalks. Additionally, CT scanning technology was employed to reveal the conical fiber structure characteristics of the stalk-ear axis connection. Additionally, a three-dimensional model was created using SolidWorks and imported into ANSYS/LS-DYNA to simulate the fracture process. For the first time, a weld point contact model was applied to analyze the stress distribution at the stalk connection, revealing that the radial tensile stress (10.52 N) was significantly higher than the axial stress (2.35 N) and tangential shear stress (3.39 N). The study also tracked the dynamic threshing process on a discrete test bench using high-speed photography, discovering that the force chain induced by corn kernel compression spreads circumferentially in a “trapezoidal” pattern. This multi-scale research method not only elucidates the microscopic mechanical response of fruit stalk fracture but also provides a comprehensive technical pathway from theory to practice for designing threshing devices that minimize kernel damage.

To precisely analyze the structural characteristics of the connection between the high-moisture corn kernel stalk and the cob axis, as well as the fracture mechanism, researchers utilized the SkyView Small Animal In Vivo CT Multi-Modality Fusion Imaging System from Guangzhou Boluteng Biotechnology Co., Ltd. to scan and image the corn cob, and three-dimensionally reconstructed the microscopic morphology of the stalk-cob axis interface for the two corn varieties “Boyun 88” and “Zhengdan 958.” The results showed that the stalk exhibits a near-conical fibrous structure, connected to the cob axis via dense organic fiber bundles. The interface contact area is relatively small (approximately 3.15 mm² for Boyun 88 and 2.73 mm² for Zhengdan 958). This connection characteristic leads to highly concentrated stress distribution under external loads, resulting in a progressive layered fracture pattern. Additionally, the scanned images clearly show a stepped layered structure at the base of the cob stalk. This unique morphology explains why the fracture force under axial and tangential shear forces is significantly lower than under radial tensile force (radial fracture force: 10.52 N, axial: 2.35 N). These structural features provide direct anatomical basis for simplifying the fruit stalk into a prismatic model with four welded joints in subsequent SolidWorks modeling, and confirm that radial force application is more likely to trigger uniform fracture across the entire interface of the fruit stalk. This lays a critical structural biological foundation for mechanical optimization of low-damage dehusking equipment (e.g., wedge-shaped protrusion angle design).

Article DOI: https://doi.org/10.3390/app15042215