AE Monitoring of Microdamages in Bioceramics for Artificial Joints under Simulated Body Environment

Microfracture process of 3 mol% yttria stabilized zirconia (3Y-TZP) for artificial joints was evaluated using the acoustic emission technique. In order to investigate the e ff ects of environment and strain rate on the microfracture process, four point bending tests were carried out in air and physiological saline (P.S.) at various loading rates. From the results of AE behavior, rapid AE increasing point was observed before the final unstable fracture. It was suggested from the previous work that the AE increasing point corresponds to the maincrack formation. The critical stress for maincrack formation, σ C , was determined from the bending stress at the AE increasing point. The critical stress as well as bending strength, σ B , decreased in physiological saline. In particular, the decrease in critical stress was remarkable. It was then understood that stress corrosion cracking (SCC) by water in physiological saline a ff ected maincrack formation rather than the final fracture. Consequently, it was suggested that the evaluation of σ C is essential for the reliability assessment of bioceramics.