HIGH-TEMPERATURE SHORT-TIME CREEP OF GRAPHITE
Constant-load tensile creep properties of four commercial grades of synthetic graphite were determined at 3000 to 530U deg F for periods of up to 8 hr. The specimens tested had a gage section of 1/4-in. diameter by 1-in. length and are heated in helium by an external graphite heater. Creep rates of 10/sup - 7/ to 10/sup -3/ sec/sup-1/ are observed at stresses of 1600 to 4000 lb/in/sup 2/. The creep rate increased continuously with increasing temperature and did not show a minimum corresponding to the peak found in the tensile strength at approximately 4500 deg F. The creep rate was lower when stress was applied parallel rather than perpendicular to the grain. Total elongations greater than 5% caused decreases in density. Elongations up to 40% and density decreases up to 18% occurred during tensile creep testing. For one grade of extruded graphite, plastic Poisson ratios of 0.18 for the stress perpendicular to the grain and 0.12 for the stress parallel to the grain were found. Activation energies of 17U to 240 kcal/mol are obtained using sion, epsilon = Ae/sup - DELTA H/RT/, the time-compensated-temperature expression T(C + log t) = constant. For some test procedures, values as low as 130 kcal/mol were found. (auth)
- Research Organization:
- California Inst. of Tech., Pasadena. Jet Propulsion Lab.
- NSA Number:
- NSA-13-008921
- OSTI ID:
- 4267982
- Report Number(s):
- JPL-EP-583
- Country of Publication:
- United States
- Language:
- English
Similar Records
HIGH-TEMPERATURE TENSILE PROPERTIES OF GRAPHITES. Progress Report
TENSILE PROPERTIES OF PYROLYTIC GRAPHITE TO 5000 F
Related Subjects
CONFIGURATION
CREEP
DENSITY
DIFFERENTIAL EQUATIONS
DUCTILITY
EXCITATION
EXTRUSION
FABRICATION
GAGES
GRAIN SIZE
GRAPHITE
HELIUM
HIGH TEMPERATURE
MATERIALS TESTING
METALLURGY AND CERAMICS
POISSON EQUATIONS
REACTION KINETICS
STRESSES
SURFACES
TENSILE PROPERTIES
THERMODYNAMICS
THICKNESS