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11 July 2002 Observation of fatigue crack growth in ferroelectrics under electrical loading
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Fatigue crack growth is studied in PZT-5H and PLZT 8/65/35 ferroelectric ceramics under purely electrical cyclic loading. The growing cracks are intergranular and exhibit features such as bifurcation, tunneling, arrest and bursts of rapid growth. Two ferroelectrics show different cracking behaviors once the crack growth commences - the crack growth rate in PZT-5H decreases with the number of cycles, whereas for PLZT 8/65/35, a period of rapid steady-state crack growth is typical. A band of damaged material forms around the crack and propagates through the ceramic. The thickness of this band of damaged material is directly proportional to the strength of the applied electric field. Crack growth measurements are presented for two ferroelectric compositions under varying load amplitude and with varying frequency and test geometry. Potential mechanisms underlying the fatigue behavior include cracking at local stress concentrations due to inhomogeneity at the grain length scale, a wedging mechanism in the crack wake, the action of the crack as a field intensifier, and the degradation of a actuating mechanism.
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Jay Shieh, Norman A. Fleck, and John E. Huber "Observation of fatigue crack growth in ferroelectrics under electrical loading", Proc. SPIE 4699, Smart Structures and Materials 2002: Active Materials: Behavior and Mechanics, (11 July 2002);

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