Controlled Walnut Shelling Through Structure‐Guided Pre‐Notches: Optimizing Kernel Integrity and Process Efficiency

ABSTRACT This study aimed to enhance mechanized walnut shelling efficiency by developing a novel pre‐treatment strategy designed to mitigate uncontrolled cracking and maximize oversized kernel yield (OKY). This study focused on establishing a directional cracking methodology derived from a walnut shell curvature mechanical analysis. The crack initiation and propagation mechanisms were elucidated within the frameworks of classical and fracture mechanics. A mechanistic model, correlating shell curvature with stress distribution, was validated using a combined approach of finite element analysis and physical compression experiments. Furthermore, a three‐factor, three‐level orthogonal experimental design was employed to systematically evaluate the effects of compression mode, notching position, and notch length. Statistical significance was assessed using p ‐values to determine the influence of these variables on the shell breakage rate (SBR) and kernel yields. Validation results confirmed the reliability of the mechanistic model regarding stress distribution. Statistical analysis indicated that the compression mode significantly ( p < 0.01) affected SBR, while notching position and notch length significantly ( p < 0.05) influenced OKY. Optimal performance was achieved using dual‐point compression, circumferential ridge notching, and a 20 mm‐notch length, resulting in a 99.05% SBR and a 94.20% OKY. These figures represent improvements of 7.55% and 9.48% over conventional shelling processes, respectively. The findings confirm that the directional notching‐assisted compression cracking approach effectively addresses the objective of reducing uncontrolled shell fracture. This study provides a robust theoretical foundation and practical parameters for the development of high‐performance, low‐damage directional nut‐shelling equipment.