Observation of Crack Propagation in Polycrystalline Ceramics and Its Relationship to Acoustic Emissions
A complete understanding of the failure processes within ceramic materials has been the goal of many studies over a considerable period of time. The achievement of this goal has been thwarted by the brittle nature of ceramics which causes failure as a consequence of stress concentrations arising at crack tips or other flaws. The nature of the ‘critical flaw’ which precipitates failure is of considerable interest to both fabricators of ceramics and to designers courageous enough to consider these materials for structural applications. The flaw theory for fracture and its development in fracture mechanics is well understood and is treated elsewhere in these proceedings. The process whereby minor defects can accumulate and form flaws of sufficient magnitude to cause catastrophic failure of the component is less well understood. This paper describes the detection and observation of discrete events taking place during loading of ceramics and which culminate in the development of a critical fracture crack.
KeywordsAcoustic Emission Crack Front Intergranular Crack Acoustic Event Slow Crack Growth
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