New experimental technique (Disk-on-Rod Test) for the evaluation of thermal shock fracture behavior of ceramics was developed. The disk specimen with 20mm radius was heated to high temperature and quenched by means of contacting with the cool metal rod. The transient temperature on the disk specimen was measured by IR camera and thermal stress was calculated by finite element method. AE signals during thermal shock fracture were detected using an AE sensor attached on the bottom of the metal rod. It was understood that the maincrack was initiated at the center of the disc specimen and it was propagated with the deflection, arrested and re-propagated after several seconds. This behavior showed good agreement with the result of the thermal stress field and AE analysis. The critical stress for maincrack formation was determined by AE analysis. Consequently, the microfracture process during thermal shock fracture was well understood.
