J. Phys. IV France 04 (1994) C8-689-C8-694
Crack stability in rate sensitive ceramics and their rate dependenceT. Nojima
Dept. of Aeronautical Engineering, Kyoto University, Sakyo-ku, Kyoto 606, Japan
The crack stability condition in rate sensitive brittle materials is analysed. The analysis shows that a crack begins to extend before a maximum load (Pmax) appears in fracture toughness (KI) tests and the extension depends on the n-value in the aαKnI relation. This suggests that the evaluation of a true KI-value is quite difficult. An analytical method for using the KIi-value (the initial stress intensity evaluated by the Pmax and initial crack length) is proposed. Experimental data for an alumina ceramic and a glass are analysed by the method. The KIi-Tf relation of the glass consists of 4 regions over the range 10-5s <Tf<107s where Tf is the time to failure.
© EDP Sciences 1994