Study of Fracture Mechanism of Machinable Mica Glass-Ceramics under Quasi-Static Conditions

Resumo

In order to study the deformation and fracture mechanism of machinable mica glass ceramics under different loading modes, quasi-static uniaxial tensile and compression experiments are designed and analyzed based on the obtained quasi-static stress-strain curves at different strain rates, the macroscopic and microscopic fracture morphology of the samples and the nano-indentation experiment. The results show that mica glass ceramics are basically elastic brittle bodies. A very short “softening” section before the compression fracture is observed. There is a significant SD (tensile and compressive strength difference) effect, and the ratio of compressive to tensile strength is 14. The fracture mechanism of mica glass ceramics is related to the loading mode. The fracture mechanism is normal tensile fracture perpendicular to the loading axis under tensile loading. Under compressive loading, there is a mixed mode of distensile splitting and local shear failure. The microcrack is preferentially nucleated and extends to the weak interface at the junction of two phases, and the critical nucleation load is about 20 mN. The energy consumption mechanism of crack initiation and propagation at the weak interface and cleavage steps are the reason for the softening of the compression end curve.