THERMAL SHOCK STUDIES OF CERAMIC MATERIALS.

A test method has been developed and used at the U. S. Naval Research Laboratory for comparing the thermal shock characteristics of several ceramic materials. The method is simple and inexpensive, making use of a circular disk of ceramic material containing a central hole. Thermal stresses are imposed by heating the inside of the central hole with a methane-oxygen torch. Thermocouples, placed at different distances from the central hole, give one information on temperature versus ti4e for various torch flame temperatures. Additional information may be obtained on crack velocities in each material by painting concentric silver strips on the disk surfaces. By connecting each strip to an oscilloscope, one may follow the path of the fracture as the crack progresses across the plate. Comparative thermal shock data were obtained for two types of alumina, a crystalline glass, and a borosilicate glass. Information obtained through these studies will be used in an attempt to correlate fracture toughness with various thermal shock parameters. Author