応力および破壊位置の確率論によるセラミックスの曲げ強度解析

抄録

In this report, we analysed the data of 3-point bending tests on Si₃N₄ and PSZ rectangular bar specimens and ZrO₂ round bar specimens. The strength distributions of Si₃N₄ and PSZ and that of ZrO₂ were representd by the multi-modal Weibull distribution and 2-parameter Weibull distribution (mono-modal), respectively. The parameters of the former were estimated with the multi-step maximum likelihood method, and those of the latter with the least square method. Using these parameters, the true stress (stress at the fracture origin) distributions were calculated on the basis of the statistical theory of stress and fracture location. As a result of comparison of the calculated distributions and experimental data, it was found that the both distributions showed good agreement.
Furthermore, on the ZrO₂ round bar specimens other bending tests were carried out, varying the specimen size and the loading method. Weibull moduli obtained in the tests were not constant. There was a tendency that they increased as the effective size decreased. We discussed the reason of this change, considering the experimental relationship between the crack size and the fracture strength.