CYCLIC FATIGUE BEHAVIOR OF PRESSURE-LESS SINTERED SILICON-NITRIDE IN ROTATING BENDING TEST

Cyclic fatigue behavior of sintered silicon nitride was investigated by the rotating bending test method. The fatigue data were analyzed using Weibull's statistical approach based on the power law crack growth relation. This analysis agreed with experimental results. The relation between the number of cycles to failure and the initial stress intensity factor calculated from the defect size measured by fractography was discussed. As a result, the fatigue failure was caused not only by the surface defects but also by the internal defects. The cyclic fatigue behavior of silicon nitride was explained by the K1-V diagram, in which the cyclic stress corrosion cracking (SCC) mechanism and the cyclic fatigue crack growth mechanism independent on SCC were taken into consideration.