Abstract: A new criterion of fracture mechanics-stochastic characteristics for ceramic tool fracture based on the analysis of its fracture features in intermittent turning is proposed in　the paper. The distribution function of theoretical tool life by fracture from the new criterion for fracture is derived. A series of experiments on strength and fracture performance for ceramic tool as well as cutting tests on tool life by fracture have been done. SEM analysis on the tool fracture faces shows that late fracture of ceramic tool appears　in fatigue character. The stresses in tool tip are analysed by finite elements method. The　modified distribution function of theoretical tool life by fracture presents a good agreement with experimental results. The AE technique is used for detecting tool fracture.

Key words: 断裂力学, 破损机理, 破损判据, 破损寿命, 陶瓷刀具