Abstract
This article is aimed at studying the strength characteristics of the shell of pine nuts in order to develop effective devices capable of accurately splitting the shell, while preserving the core. Rheological properties were analyzed under static and impact loading. Static tests used the ST-2 structurometer with three indenters: Tarr-Baker, 45° cone, and 90° cone. Results showed that a 90° cone indenter at 15–16% shell humidity ensures optimal energy efficiency and kernel safety.Impact tests utilized a custom setup with a jagged load at a 90° angle, dropped from a controlled height. The best cracking occurred at 0.24–0.26 J, corresponding to 35–40 m/s. Theoretical analysis classified pine nut shells as thin-walled spherical structures, allowing the application of structural mechanics principles. Brittle fracture behavior, critical stress thresholds, and impact kinetic energy were studied and experimentally validated.A review of existing devices identified pneumatic dispersion as the most gentle cracking method, though limited by low aerodynamic resistance and acceleration distance. To overcome these challenges, a new two-stage device was developed. It first accelerates nuts using a high-speed toothed disc, followed by compressed air propulsion, reducing kernel damage and improving efficiency.The proposed device enhances pine nut processing for the food and pharmaceutical industries.