Static and Cyclic Fatigue of Alumina at High Temperatures

Fatigue behavior of alumina at 1200°C was investigated. Uniaxial tensile tests were conducted in both static and cyclic loading. A variety of loading wave forms were applied during the cyclic tests. Cyclic lifetime is found to be cycle shape dependent and controlled by the duration of the hold time at the maximum tensile stress in a cycle. Cyclic loading with a higher strain rate and a short duration of maximum stress during each cycle provides a beneficial effect on lifetime in comparison to static loading at the same maximum stress. The time to failure for cyclic loading with a longer hold time at maximum stress is very close to the static loading lifetime. Viscous boundary phase may be the primary contributor to the improved cyclic fatigue resistance for cyclic loading with a short duration of maximum stress.