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기술보고서

기술보고서 게시판 내용
타이틀	Large-Scale Weibull Analysis of H-451 Nuclear- Grade Graphite Specimen Rupture Data
저자	Nemeth, Noel N.;; Walker, Andrew;; Baker, Eric H.;; Murthy, Pappu L.;; Bratton, Robert L.
Keyword	FLEXING;; GRAPHITE;; HIGH TEMPERATURE GAS COOLED REACTORS;; NUCLEAR REACTORS;; POSITION (LOCATION); STOCHASTIC PROCESSES;; STRESS-STRAIN RELATIONSHIPS;; TENSILE STRENGTH;; WEIBULL DENSITY FUNCTIONS
URL	http://hdl.handle.net/2060/20130001714
보고서번호	NASA/TM-2012-217409
발행년도	2012
출처	NTRS (NASA Technical Report Server)
ABSTRACT	A Weibull analysis was performed of the strength distribution and size effects for 2000 specimens of H-451 nuclear-grade graphite. The data, generated elsewhere, measured the tensile and four-point-flexure room-temperature rupture strength of specimens excised from a single extruded graphite log. Strength variation was compared with specimen location, size, and orientation relative to the parent body. In our study, data were progressively and extensively pooled into larger data sets to discriminate overall trends from local variations and to investigate the strength distribution. The CARES/Life and WeibPar codes were used to investigate issues regarding the size effect, Weibull parameter consistency, and nonlinear stress-strain response. Overall, the Weibull distribution described the behavior of the pooled data very well. However, the issue regarding the smaller-than-expected size effect remained. This exercise illustrated that a conservative approach using a two-parameter Weibull distribution is best for designing graphite components with low probability of failure for the in-core structures in the proposed Generation IV (Gen IV) high-temperature gas-cooled nuclear reactors. This exercise also demonstrated the continuing need to better understand the mechanisms driving stochastic strength response. Extensive appendixes are provided with this report to show all aspects of the rupture data and analytical results.