Experimental and FEM research on Camellia oleifera shell structural–mechanical cracking behavior during hulling

Abstract

AbstractCamellia oleifera shell (COS) mechanical–structural property and cracking behavior are crucial for hulling, hulling work can improve the extraction oil quality. A developed texture analyzer with in situ observation is built for COS mechanical–structural and crack testing. Influencing factors are studied under working effects, considering fruit size, drying temperature, compression distance, speed, directions. The shell compression damage is analyzed with compression damage model. Results show that COS compression damage can be divided into three stages: shell elastic deformation, initial cracking, crack propagation. Compression force decreases rapidly after initial cracking, increases with cracking propagation. Compression direction leads different cracking, cracking load Fx > Fy. Shell cracking force increases with increasing compression speed, distance, fruit diameter, leading intensified crack. Cracking force decreased with drying temperature increasing in 20–110°C, obvious at 80°C. FEM simulation matches COS cracking behavior, stress concentration increases at apical. The research provides theoretical basis for hulling design.Practical applicationsCamellia oleifera shell (COS) mechanical–structural property and cracking behavior were crucial for shelling, hulling work improves the extraction oil quality. COS cracking behavior were studied under various working effects such as fruit size, drying temperature, compression distance, speed, and direction, and providing a theoretical basis for improving hulling methods. Based on the actual hulling process, research on temperature factors has been added, and the conclusion that the optimal drying temperature is 80°C has been proposed. Considering energy conservation and tea oil quality, hulling efficiency has been improved. Meanwhile, cracking behavior and mechanical properties were studied from cracking in three stages, preventing excessive extrusion caused to seeds damage in hulling. The research provides theoretical basis for hulling design and optimization.