Exponential slow crack growth of glass and advanced ceramics - dynamic fatigue

The life prediction analysis based on an exponential crack-velocity formulation was made and examined using a variety of experimental data on glass and advanced structural ceramics in constant stress-rate ('dynamic fatigue') loading at ambient and elevated temperatures. The data fit to the relation of strength versus In (stress rate) was very reasonable for most of the materials. The major limitation in the exponential crack-velocity formulation, however, was that the inert strength of a material must be known a priori to evaluate the important SCG parameter, n, a significant drawback as compared with the conventional power-law crack-velocity formulation.