For investigating the relation between material morphology and mechanical parameters, the fracture morphology of double torsion specimens of layered slate was analyzed by adopting Talysurf CLI 20003D laser profilometer. It is found that the fractal dimension can be used to represent the fracture section resulting from crack growth. The actual propagation length of the crack was calculated with fractal dimension ( D2 ) of the contour line for the fractured surface. Result showed that the measurement had a great influence on the determination of the actual propagation length of cracks. A higher D2 value led to propagation length more vulnerable to the variation of measurement. Then, the fractal model of stress intensity factor KⅠ relative to the rate was derived based on Paris formula. It is found that D2 can be fit linearly with index parameter n of KⅠ.%为探讨裂纹演化过程中材料形貌与力学参数的关系,采用Talysurf CLI 2000三维激光形貌仪对层状岩样双扭试件断口形貌进行了扫描分析,结果表明,分形维数能较好地表述裂纹扩展形成的断口断面;利用轮廓线分形维数D2对裂纹真实扩展长度进行计算,结果表明,测度对确定裂纹实际扩展长度影响较大,且D2值越大,扩展长度对测度变化越敏感.运用Paris公式推导了与速率有关的应力强度因子KⅠ的分形模型,结果表明,D2与KⅠ的指数参数n线性拟合较理想.
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