Strength ceramic

Many distribution functions can be apphed to strength data of ceramics but the function that has been most widely apphed is the WeibuU function, which is based on the concept of failure at the weakest link in a body under simple tension. A normal distribution is inappropriate for ceramic strengths because extreme values of the flaw distribution, not the central tendency of the flaw distribution, determine the strength. One implication of WeibuU statistics is that large bodies are weaker than small bodies because the number of flaws a body contains is proportional to its volume. 

FIGURE 17.2 Grinding direction and the effect on ceramic strength. Refer to Figure 17.1 for crack nomenclature and orientation. 

Mechanical stability against thermal cycling between ambient temperature and Top requires matching of thermal-expansion coefficients of the electrolyte and electrodes, the interconnects, and the seals. Note Ceramic strength is improved where cell design retains the ceramic membrane under a compressive stress. 

G.K. Bansal and W.H. Duckworth, Effects of Specimen Size on Ceramic Strength, in Fracture Mechanics of Ceramics (1978), 3, p. 189 edited by R.C. Bradt, D.P.H. Hasselman and FT. Lange, Plenum Press, New York. 

Pourcel, F., Jomaa, W., Puiggali, J.-R., Rouleau, L., 2007a. Criterion for crack initiation during drying alumina porous ceramic strength improvement Powder Technol. 172 120-127. 

The fracture energy value that often features in theoretical discussions on ceramic strength for normal polycrystalline material is the specific fracture energy of the grain boundaries y . Unfortunately, y is hard to measure directly and so almost no experimental data exist. It is common to see y approximated to lattice fracture energy y as a fraction ranging... 

Equation (5.67) is telling us that the ceramic strength is controlled by the indentation flaw c, but two points must be remembered. First, the size of the radial c may increase due to stress corrosion to a value c before the sample is loaded in tension to breaking. And, second, we must consider the residual crack driving force, arising from the permanently deformed... 

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