ABSTRACT
Real-life engineering environments involve a complex combination of stress, temperature, environmental factors, and other factors impacting on the ceramic. This chapter discusses these "time-dependent" degradation mechanisms plus other environmentally induced sources of failure: creep, slow crack growth, chemical attack, mechanically induced effects and thermal shock. The term creep is normally used to refer to deformation at a constant stress as a function of time and temperature. Static fatigue, also known as stress rupture, involves subcritical crack growth at a stress that is lower than required for instantaneous fracture. Static fatigue is not restricted to high temperatures. It also occurs at room temperature for silicate glasses and for many other ceramics. The mechanism involves localized corrosion at the crack tip or where stress is concentrated at a flaw. The corrosion is accelerated by the presence of water or, in some cases, other chemicals.
