Contrary to traditional notions, recent studies in several engineering ceramics have provided persuasive evidence of degradation and premature failure under cyclic loading. In the present study, such cyclic fatigue-crack propagation behavior is investigated in a range of advanced ceramic materials, including monolithic alumina, partially-stabilized zirconia (PSZ), zirconia-toughened alumina (ZTA), graphite, and silicon nitride. Cyclic crack-growth is unequivocally demonstrated for tension-tension loading; growth rates over the range 10−10-10−6 m/cycle are found to be power-law dependent on the stress intensity range, and to exhibit mean-stress, crack-closure, frequency, and environmental effects, analogous to behavior in metals. In addition, transient growth rate behavior following block loading sequences, anomalous growth rate behavior of small fatigue cracks, and comparisons of stress-corrosion crack growth under monotonic loads with cyclic crack velocities are reported. Mechanisms for such cyclic fatigue behavior are described.
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