玉米种子内部机械裂纹产生与扩展的微观机理

Micromechanism of Inner Mechanical Cracks Generation and Expansion of Corn Seed Kernel

应用Cottrell位错塞积模型分析了玉米种子内部机械裂纹产生机理,采用Griffith能量平衡理论和分形几何理论推导了机械裂纹扩展速度与扩展路径维数计算公式,并对内部机械裂纹扩展速率进行分形分析。结果表明:当玉米种子局部所受应力达到一定时,其内部即产生机械裂纹;根据玉米种子内部机械裂纹扩展运动学公式,内部裂纹扩展宏观速度小于分形扩展速度;由玉米种子内部机械裂纹扩展路径的分形维数公式求出其维数为1.139 5;淀粉颗粒尺寸相同时,裂纹沿淀粉颗粒扩展的速率最快。

Mechanism of inner mechanical cracks of corn seed kernel was researched by means of Cottrell piling up of dislocation theory. The formula of expanding speed and propagation route dimension of inner mechanical cracks were inferred based on theory of Griffith energy balance and fractal geometry. Crack growth rate was analyzed through fractal method. The results showed that inner mechanical cracks of corn seeds formed when part stress increased to a certain level. According to phoronomics formula of inner cracks propagation, the macro-speed propagation was less than fractal propagation speed. Fractal dimension of 1. 139 5 was calculated by path formula of mechanical cracks propagation. The speed of cracks propagation along starch particles extending was faster than same size of starch particles.