Crack length and specimen size influences on fracture strength of brittle materials

摘要

The influences of crack length and specimen size on the fracture strength of brittle materials in both tension and frictional compression are studied in the framework of the boundary element method. The coefficients representing the coupling between the cracks and finite-sized boundary are obtained in the form of algebraic expressions. The curved propagating trajectories are simulated through a stepwise propagation process. With different configurations of specimen size, crack length and frictional coefficient in compression, the related strength size effects are obtained. It is found that the usual size effects with -1/2 slope in the bilogarithmic form are only applicable to the geometrically-similar cases (with the same crack to specimen scaling ratios— assumption commonly used but not practical). For the case of the fixed specimen size with varying crack length in both tension and frictional compression, the influences of crack length on the failure stress are more severe than for those of the geometrically-similar cases.