1991 Volume 40 Issue 458 Pages 1491-1496
Static and cyclic fatigue tests were made on glass, glass ceramics and silicon nitride under static tensile loading and tension-compression cyclic loading at various stress ratios between R=-1 and 1, by using an apparatus specially designed with a device to minimize the load eccentricity. Crack growth tests were also made under static loading and cyclic loading in order to obtain the crack growth rate da/dt, as a function of stress intensity factor K. Test results on smooth round bar specimens show that almost no effect of stress cycling was seen on silicon nitride A and borosilicate glass, while appreciable degradation in strength due to cyclic loading was observed on glass ceramics and silicon nitride B. The relation, da/dt versus K, of small cracks obtained from the tensile test on smooth round bar specimens showed higher values than those of large cracks obtained from the crack growth tests. The increase in crack growth rate due to cyclic stress was observed in both silicon nitride B and A, in the latter of which no effect of stress cycling was observed in the tests on smooth round bar specimens.
