Effect on Vibrated Cyclic Fatigue Properties of Ceramics from Stress Load Condition

The effect of external conditions, such as cyclic frequency, wave form and stress amplitude, on the cyclic fatigue properties of ceramics has not been analyzed sufficiently at frequencies higher than 10Hz, because of the restriction of testing device. A cyclic fatigue phenomenon of ceramics was tested at the range from 30 to 150Hz by a Piezo-Stack type device, which can control external stress conditions accurately by adjustment of input voltage. Samples used were ZrO2, Al2O3, Mg2SiO4 and SiC. The estimation of the change in fatigue properties with an external condition was established by following the methods. (1) The estimated methods by an experimental equation (V=AK1n) between subcritical crack growth velocity (V) and stress intensity factor was modified with a concept of a fatigue limit. (2) The initial crack length in each sample, which caused the scattering of fatigue life, was estimated. In oxide ceramics, the cyclic fatigue properties can be estimated practically by the same crack growth equation, even though the cyclic frequency changed from 30 to 150Hz. However, when the wave form was changed, the experimental fatigue life did not always correspond to the estimated life, but the cyclic effect can be predicted with regard to crack growth.