SEDL / STP / STP1201-EB / STP12781S

Lifetime Prediction for Ceramic Materials Under Constant and Cyclic Load

Fett, T
Research Engineer, Kernforschungszentrum Karlsruhe, Institut für Materialforschung II,

Munz, D
Professor, Universität Karlsruhe, Institut für Zuverlässigkeit und Schadenskunde im Maschinenbau, and Kernforschungszentrum Karlsruhe, Institut für Materialforschung II, Karlsruhe,

Pages: 14    Published: Jan 1994

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Abstract

Subcritical crack growth under static and cyclic loads is an important failure mode and often responsible for delayed failure. At least for subcritical crack extension under constant load it is a well-known fact that the crack growth behaviour of natural cracks differs significantly from that of macroscopic cracks, especially for such materials exhibiting a pronounced R-curve behaviour. The influence of bridging surface interactions — responsible for R-curves in alumina (Al2O3) — will be discussed with respect to strength and static lifetimes. Experimental results obtained for both loading cases are presented for alumina. Measured lifetimes are significantly shorter than the predictions and a reduction of lifetimes is found for increasing frequencies. From these results an effect of cycles becomes obvious and it can be concluded that a real cyclic fatigue effect occurs.