Mechanistic analysis of fracture-controlled canola dehulling via finite element modeling

Canola is an important oilseed crop valued for its oil and protein, both of which reside primarily in the kernel. Dehulling separate the hull from the kernel and is important for improving product quality. This study aimed to engineer a controlled fracture-propagation pathway that maximizes hull removal while preserving kernel integrity. Canola was first hydrated and dried using a fluidized bed dryer (FBD) to tailor the mechanical properties, followed by mechanical loading using a roller machine that generated either compression-dominated or shear-dominated stresses. Finite element modeling and experimental validation were combined to reveal how pretreatment and stress mode shape fracture initiation, propagation, and hull detachment dynamics. The 2D model characterized the mechanical properties of the hull and kernel based on uniaxial compression tests, while the 3D model simulated deformation and stress distribution during the dehulling process. High-speed imaging captured real-time dehulling behavior, and synchrotron-based X-ray tomography visualized internal fracture patterns and kernel preservation. FBD pretreatment significantly reduced hull strength and increased kernel elasticity, specifically the lowest ultimate stress of 11 MPa in the hull and the elasticity of 30.5 MPa with the kernel, creating a favorable mechanical contrast that promoted preferential hull rupture and clean hull-kernel separation while minimizing kernel damage. The shear-dominant mode further promoted directional crack propagation and hull detachment, resulting in substantially improved recovery of intact, hull-free kernels. These findings establish a mechanistic foundation for precision-controlled fracture and separation processes across food, agricultural, and biomaterial systems.