Fracture behaviour of alumina ceramics by biaxial ball-on-3-ball test

The fracture behaviour of alumina ceramics was studied using a biaxial ball-on-3-ball test. The polished surfaces of the alumina specimens were indented at positions 0, 1, 2 and 3 mm distant from the center of the specimen along a path (A), passing through the middle point between two supporting balls from the center of the specimen, and also along a path (B), passing through the top point of a supporting ball from the center of the specimen. The fracture strength of the indented specimens was measured using the biaxial ball-on-3-ball test. The fracture strength increased with increasing distance of the indented position from the center of the specimen. The fracture strength of the specimen indented along a path (B) was higher than that of the specimen indented along a path (A). It was also found that the fracture was brought about by the tangential stress rather than the radial stress when the indentations were made at points 1 and 2 mm distant from the center of the specimen. The results were in good agreement with the results of finite element analysis.