Bending tests of TZP-ceramics with notches and flaws based on mesomechanical simulation

According to linear elastic fracture mechanics, the relation of fracture stress and crack size should be a straight line in logarithm diagram. Thereby the fracture stress should be much higher than that in tests for a ceramic specimen containing a small notch. Quite a few publications testified and argued this phenomenon, but no final conclusion was drawn. In this dissertation 3Y-TZP bending specimens were notched to the depth in range from 10µm up to 1.3mm and subsequently 4PB tests were carried out. The difficulty lies in notching procedure and ensuring the initiation from the notch. The relation of fracture stresses and notch size were discussed through fitting function proposed by Usami and Taylor respectively. Microstructural anisotropy at lattice level was hypothesized, which was quantified by Zener ratio. The 4PB tests were simulated with FEM containing cracks from 12.5µm to 0.8mm employing multiscale method. The critical stress intensity factor was calculated at the lowest crack tip vicinity level considering the anisotropic microstructure. The influence of the crack size on the simulated fracture stresses of isotropic and anisotropic materials would be compared with experiments.