A direct examination of the fracture strength-defect size relationship in alumina ceramics

This paper reports a new approach to the strength-defect relationship for ceramics with an alumina cs as a model material. Optical microscopy of transmission mode was applied to characterize defects in alumna ceramics. This method is superior to any other methods in collecting detailed information on large defects in ceramics. The bulk examination on thinned specimen is crucial for detecting few relatively large defects, one of which could behave as a potential fracture origin. A distribution curve is constructed for the defect sizes and their concentrations. This curve is applied to estimate the strength variation of the ceramics through the fracture mechanics. The estimated strength distribution was compared with the results of direct measurement to determine the relationship between the fracture strength and the defect size. The defect size distribution can successfully explain the strength distribution of the ceramics.