ANALYSIS OF DYNAMIC FRACTURE-BEHAVIOR OF PARTIALLY-STABILIZED ZIRCONIA AT ELEVATED-TEMPERATURES BY THE METHOD OF CAUSTICS

The validity of the caustic method on fracture problems of partially s tabilized zirconia at room and elevated temperatures up to 1200-degree s-C is confirmed, and we investigated the dynamic fracture behavior of this material from pictures taken using the apparatus of caustics tog ether with an ultrahigh-speed camera, Imacon 790. Consequently, it is revealed that dynamic fracture toughness K(Id) abruptly decreases as t he testing temperature increases over about 500-degrees-C, and the rat io of K(Id) to static fracture toughness is increased from 2.0 at room temperature to 5.0 at 800-degrees-C. Moreover, it is ascertained that the crack-propagation fracture toughness is increased with the crack velocity at any testing temperature up to 1200-degrees-C, and this ten dency is decreased with the rise of temperature in this range. Finally , an example of the visualized acoustic emission (AE) wave is shown. I t is revealed that the velocity of this AE wave decreases slightly as the temperature rises, and it coincides with the Rayleigh wave speed o f this material.