Lifetime prediction of structural ceramics by dynamic fatigue

The dynamic fatigue behaviour of Al₂O₃ structural ceramics was studied by loading the stress on the specimen at a constant stress rate. The fracture strength of Al₂O₃ specimens under dynamic mode was constant up to a critical stress and then the lifetime abruptly decreased to zero as predicted theoretically for both the single cycle and the repeated loading. The material constant A was nearly constant and has no relation with loading mode and down speed for unnotched and notched specimen. The fracture strength obtained by theoretical calculation from the constants n and A was in good agreement with the measured value.