1989 Volume 38 Issue 430 Pages 783-788
Application of ceramics to mechanical and structural components requires, for a strength design or a quality control, to deal with the strength as a material constant independent of either testing methods or the shapes and sizes of specimens. Therefore, we propose the analysis method for estimating commonly the material intrinsic strength from all the data obtained by tensile, bending, creep and fatigue tests at the same temperature. The fracture strength of commercial engineering ceramics is assumed to be governed by crack growth properties from an initial flaw larger than a grain size by about more than ten times. If the strength data from all the tests are analyzed according to Weibull statistics in considering the effective hold time of applied stress and the effective volume at the same time, the strength can be expressed commonly as follows
σf(Nfteff)nf=σf0m√ln(1-Pf)-1/Veff
where nf is the strength decrement index and equals to the inverse of crack growth rate index n, and σf0 is the strength normalized for cumulative effective hold time Nfteff=1(sec) and effective volume Veff=1(mm3).
The estimating method proposed here is useful for making a reliability design or a quality control for ceramic components requiring lot quality checks.
