A GEOMETRICAL ASSESSMENT OF MACHINED CERAMIC SURFACE FOR ESTIMATING FATIGUE-STRENGTH

Effects of surface micro-geometry on fatigue strength of silicon nitride(Si3N4) were discussed and the data-processing techniques for a geometrical assessment of its surface finish were developed. Taking no account of conventional roughness standards, new topographical parameters based on profile valleys were proposed to correlate with the fatigue strength of test Specimens. The sampling conditions and the calculation method were examined in detail. Judging from the experimental results of fatigue tests, it was made clear that the fatigue strength of Si3N4 can be estimated to some extent with the statistical values on the micro-geometry at the bottom of valleys. The metrological discussion on the correlation was also made.