Title

Factors Affecting Thermal Shock Resistance Of Polyphase Ceramic Bodies

Date

1962

Index Abstract

Contrails and DTIC truncated

Photo Quality

Incomplete

Report Number

WADD TR 60-749 Part II

Creator

Shaffer, P. T. B.

Hasselman, D. P. H.

Corporate Author

The Carborundum Company, Research and Development Division, Niagara Falls, N.Y.

Laboratory

Directorate of Materials and Processes

Extent

167

Identifier

AD0277605

AD0277605

Access Rights

OTS

Distribution Classification

1

Contract

AF 33(616)-6806

DoD Project

7350

DoD Task

73500

DTIC Record Exists

Yes

Distribution Change Authority Correspondence

None

Report Availability

Full text available

Date Issued

1962-04

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 resistance of the zirconium carbide is to reduce the degree of damage resulting from fracture 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 conductivity, 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. Excellent agreement with experiment was show. Calculations were carried out of the transient temperatures and thermal stresses in a sphere subjected to thermal shock in a medium with constant surface heat transfer coefficient It was found that at the time of maximum stress the sphere is still close to its initial temperature. Using, these results thermal shock data in the literature were recalculated. Good agreement with experiment was shown.

Subject

Mechanical Properties

Refractory Materials

Thermal Conductivity

Thermal Expansion

Thermal Radiation

Thermal Stresses

Publisher

Wright-Patterson Air Force Base, OH : Directorate of Materials and Processes, Aeronautical Systems Division, Air Force Systems Command

Distribution Conflict

No

Provenance

IIT

Type

report

Format

1 online resource