Fatigue of Ceramics (Part 3)

To understand the fatigue behavior of ceramics, the equipment for the tension-compression axial cyclic fatigue testing of ceramics at high temperature was successfully developed. The tension-compression cyclic fatigue tests and the tensile static fatigue tests were carried out up to 1000°C using sintered silicon nitride. At high temperature, the cyclic fatigue did depend on frequency. The lower the frequency became, the less the fatigue resistance became. The failure diagram was constructed to show the effects of mean stress and stress amplitude on the fatigue strength. It is concluded that a design methodology proposed for the metal fatigue is applicable to the sintered Si3N4 examined in this study. Microstructural observations suggest that the progress of cyclic fatigue of the sintered Si3N4 is caused by slow crack growth and creep defomation.