Accession Number : AD0277605

Title :   FACTORS AFFECTING THERMAL SHOCK RESISTANCE OF POLYPHASE CERAMIC BODIES

Corporate Author : CARBORUNDUM CO NIAGARA FALLS N Y

Personal Author(s) : HASSELMAN,D.P.H. ; SHAFFER,P.T.B.

Report Date : APR 1962

Pagination or Media Count : 1

Abstract : An investigation of the material properties which affect the thermal shock resistance of polyphase ceramic systems composed of a high Young's modulus continuous phase containing a low Young's modulus dispersed phase has been conducted using the model system zirconium carbide-graphite. The principal effect of the dispersed phase of graphite on the thermal shock resistanc of the zirconium carbide is to reduce the degree of damage resulting from frac ure by thermal shock. The presence of the graphite also causes a decrease in strength and Young's modulus of elasticity in such a manner as to decrease the elastic energy stored at fracture and at higher volume fractions graphite to increase the extensibility (i.e., strain at fracture). Suitable thermal shock damage resistance factors were derived. The coefficient of thermal expansion and Poisson's ratio to a first approximation were independent of graphite content. Due to the relative differences in thermal properties the graphite causes an increase in thermal con uctivity, thermal diffusivity and emissivity. Porosity was found to be a major variable. Emissivity (absorptivity) was introduced as a variable affecting thermal shock resistance of ceramic materials. A quantitative theory of thermal shock by radiation was developed. (Author)

Descriptors :   MECHANICAL PROPERTIES, REFRACTORY MATERIALS, THERMAL CONDUCTIVITY, THERMAL EXPANSION, THERMAL RADIATION, THERMAL STRESSES

Distribution Statement : APPROVED FOR PUBLIC RELEASE