Biaxial flexural strength distribution of thin ceramic substrates with surface defects

The statistical models of the strength of thin ceramic substrates with surface defects under piston-on-3-ball loading conditions are formulated using Batdorf’s statistical theory and Kirstein and Woolley’s moment equations. These models possess the form of a Weibull distribution function, making it possible to process the piston-on3-ball biaxial flexural strength data using a Weibull treatment. During this study, it was noted that the thickness of the specimen had no effect on the failure distribution. Therefore, it was deemed that a reasonable thickness of the specimen disk could be selected for the piston-on-3-ball test in the case where the thickness is so small that the deflection of the center of the specimen exceeds half of the thickness (this thickness would invalidate the strength evaluation equation specified in ASTM F 394-78). The strengths of seven different compositions of 8YSZ with dopants were tested using the piston-on-3-ball method. The results were then processed using the derived models. The failure distributions of the different thickness groups of 8YSZ specimens were similar, verifying that the thickness, indeed, has no effect on the failure distribution.