TENSILE AND CREEP BEHAVIOR OF GRAPHITES AT TEMPERATURES ABOVE 3000 F. Progress Report
The work described is taken from studies using fifteen variously selected blocks of synthetic graphite. Measurements were made at temperatures above 3000 deg F. At 5000 deg F the tensile ductility of one block tested decreased from 40 to 1% when the strain rate was increased from 5 x 10/sup -5/ to 1 x 10/sup -2/ sec/sup -1/. The strength increased slightly. At 4650 deg F the tensile creep rate for another block tested was proportiomal to the square of the applied stress. At 4800'F a specimen from another block which had been pre- heated to 5100 deg F had a creep rate of 1.5 x 10/sup -5/ sec/sup -1/, under a stress of 2800 psi, as compared to a creep rate of 4 x 10/sup -5/ sec/sup -1/ for a specimen which had not been pre-heated. Analysis of the creep data was attempted in terms of three different creep equations. The equation epsilon = A + B log t + Ct gives the most satisfactory description of the data in agreement with Imvidson and Losty. B and C were found to be Arrhenius functions of the temperature and there is evidence that they represent two distinct thermally activated processes. Creep recovery can be approximated by a logarithmic time dependence, though a distribution of relaxation processes is a better approximation. (auth)
- Research Organization:
- California Inst. of Tech., Pasadena. Jet Propulsion Lab.
- NSA Number:
- NSA-14-015983
- OSTI ID:
- 4183909
- Report Number(s):
- JPL-PR-30-18
- Country of Publication:
- United States
- Language:
- English
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