Gd. Zhan et al., Cyclic fatigue crack growth behaviour in beta-(Si-Al-O-N) at ambient and elevated temperatures, J MATER SCI, 33(15), 1998, pp. 3867-3874
Four-point bending fatigue tests on a hot-pressed sintered Sm-beta-(Si-Al-O
-N) ceramic were conducted at room temperature, 900 degrees C and 1000 degr
ees C in air under different load ratios and cyclic frequencies. The growth
of indentation cracks was measured during the fatigue tests. The results i
ndicate that the cyclic fatigue crack growth threshold is lower a nd crack
growth rates are higher, for given values of K-max at 1000 degrees C than t
hose at room temperature. The cyclic fatigue crack growth behaviour at 900
degrees C is similar to that at room temperature. It was found that the cra
ck growth retardation due to cyclic fatigue loading is much more pronounced
at higher frequencies. An increase in cyclic frequency from 1 to 10 Hz cau
se a reduction of up to two orders of magnitude in crack propagation rates.
High-temperature cyclic fatigue crack growth rates increased and threshold
stress intensity factor ranges decreased with increasing load ratio. Possi
ble mechanisms for cyclic crack growth are discussed. (C) 1998 Kluwer Acade
mic Publishers.