| When many glasses and ceramic materials are subject to static loading as well as a chemically reactive environment, they often experience delayed failure due most likely to stress-assisted chemical reactions at the cracks: pre-existing surface flaws grow to a critical length, at which point unstable rapid crack propagation ensues, leading to catastrophic failure. For a given material and ambient environment, the lesser the applied stress, the longer the time to fracture. When the applied stress decreases to a threshold level, known as a fatigue limit or a stress corrosion limit, failure of the solid can be avoided.; The mechanisms could be very different under different mechanical and chemical conditions in different solids. We adopt one possible mechanism, which was first proposed by Charles and Hillig in 1961, and develop a numerical approach to predict the fatigue threshold of brittle solid and investigate the nature of crack propagation. Numerical simulations in this dissertation have confirmed many features of stress-assisted corrosion problem and some surprising new insights emerge from calculations. In particular, we find that the behavior of fatigue limit of material is dependent not only on the driving force for material removal, but also on the kinetics of this process. Finally, further calculations have been conducted to investigate the evolution of crack propagation in composite materials. Systematic parametric studies are used to illustrate the influence of material properties and loading on crack path and growth rate along a bi-material interface. |
