Strength testing of production grade H-451 graphite; lots 472, 478, and 482

Technical Report · Tue Mar 01 04:00:00 EST 1977

DOI:https://doi.org/10.2172/7220891· OSTI ID:7220891

Engle, G B; Price, R J

Ninety-eight production logs of H-451 graphite, from three separate extrusion lots, were sampled for tensile testing. Eight replicate axial specimens from the midlength center and four replicate radial specimens from the end center of each log were tested. The axial strengths (average value 12.7 MPa) showed wide lot-to-lot and log-to-log variations, while the radial strengths (average value 15.8 MPa) were more uniform. Statistically based acceptance criteria which could be used for assigning a log to a minimum strength category were derived for two alternative definitions of ''minimum'' strength. The first definition would require 90 percent of the material at the midlength center of the log to exceed the specified minimum strength, with 90 percent confidence (90/90); the second, more stringent, definition would require 99 percent of the material to exceed the specified minimum, with 95 percent confidence (99/95). If three minimum strength categories are assumed, with category A requiring a minimum strength of 10.3 MPa, category B requiring 8.3 MPa, and category C requiring 5.5 MPa, use of the 90/90 definition of minimum strength would cause the rejection of two logs. Use of the 99/95 definition of minimum strength would increase the number of rejected logs to 18; however, this would include only 2 out of the 56 logs in the best extrusion lot. Decreasing the number of tests per log from eight to four would cause only small differences in the yields of logs accepted in each category.

• Research Organization: General Atomic Co., San Diego, CA (USA)
• OSTI ID: 7220891
• Report Number(s): GA-A-14269
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360603* -- Materials-- Properties
CARBON
ELEMENTS
GRAPHITE
MATERIALS TESTING
MECHANICAL PROPERTIES
NONMETALS
STANDARDS
TENSILE PROPERTIES
TESTING
VARIATIONS
YIELD STRENGTH