Abstract
Thermal shock fracture behavior of alumina ceramics under unbalanced thermal stress state was characterized using the Disc-on-Rod (DoR) test. In this test, the thermal stress distribution was calculated from the temperature distribution measured using an infrared camera by the finite element analysis. Furthermore, microfracture process was monitored by acoustic emission (AE) technique during thermal shock fracture. Therefore, transient thermal stress field and microfracture process were characterized dynamically and simultaneously. Using elliptical specimens and elliptical rods, unbalanced biaxial thermal stress state was obtained. Consequently, the stress ratio at the center of the specimen was controlled to designated value. And it was confirmed that unstable crack propagated immediately after the formation of the maincrack since the rapid increasing point of cumulative AE energy was detected at the fracture. And a macroscopic crack initiated perpendicularly to the first principal stress direction at the maximum stress point and crack growth path was branched from the fracture origin.
