Study on crushing characteristics of brown rice with different spike positions

BACKGROUND Rice, as a primary grain crop, is prone to breakage during harvesting and processing when mechanical forces exceed the grain's strength limit. Grain breakage not only reduces its edible and market value but also increases the risk of pests and diseases during storage. Studies have shown significant differences in the morphological structure and mechanical properties of grains at different spike positions (upper, middle, and lower) on the same rice spike. However, research on the influence of spike position on grain breakage remains limited. RESULT Using brown rice from the upper, middle, and lower spike positions as the research subject, this study precisely reconstructed three‐dimensional (3D) contour models of the embryo, endosperm, and outer epidermis for each spike position based on X‐ray computed tomography (CT) and image processing technology. Discrete element simulation parameters were calibrated using response surface optimization design. A punching test setup was established to extract and characterize internal crack patterns under varying impact forces. The results showed that the critical static loads for grains at different spike positions were 102.4 ± 16.2 N (upper), 94.5 ± 10.6 N (middle), and 93.0 ± 11.3 N (lower). Due to differences in breakage models, the optimal calibrated parameters varied by spike position, but errors remained below 5%. The volume of impact‐induced cracks increased with force. CONCLUSION Under the same force, upper grains were less prone to breakage than middle and lower grains, indicating that impact resistance followed the order: upper > middle > lower. These findings provide a key reference for optimizing agricultural machinery design to minimize grain damage.