Experimental and statistical requirements for developing a well-defined K/sub IR/ curve. Final report

Technical Report · Sun May 01 04:00:00 EDT 1977

DOI:https://doi.org/10.2172/7304006· OSTI ID:7304006

Server, W. L.; Oldfield, W.; Wullaert, R. A.

Further development of a statistically well-defined reference fracture toughness curve to verify and compliment the K/sub IR/ curve presently specified in Appendix G, Section III of the ASME Code was accomplished by performing critical experiments in small specimen fracture mechanics and improving techniques for statistical analysis of the data. Except for cleavage-initiated fracture, crack initiation was observed to occur prior to maximum load for all of the materials investigated. Initiation fracture toughness values (K/sub Jc/) based on R-curve heat-tinting studies were up to 50 percent less than the previously reported equivalent energy values (K*/sub d/). At upper shelf temperatures, the initiation fracture toughness (K/sub Jc/) generally increased with stress intensification rate. Both K/sub Jc/--Charpy V-notch and K/sub Ic/--specimen strength ratio correlations are promising methods for predicting thick-section behavior from small specimens. The previously developed tanh curve fitting procedure was improved to permit estimates of the variances and covariances of the regression coefficients to be computed. The distribution of the fracture toughness data was determined as a function of temperature. Instrumented precracked Charpy results were used to normalize the larger specimen fracture toughness data. The transformed large specimen fracture toughness data are used to generate statistically based lower-bound fracture toughness curves for either static or dynamic test results. A comparison of these lower bound curves with the K/sub IR/ curve shows that the K/sub IR/ curve is more conservative over most of its range. 143 figures, 26 tables.

• Research Organization: Fracture Control Corp., Goleta, CA (USA)
• OSTI ID: 7304006
• Report Number(s): EPRI-NP-372
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
220200 -- Nuclear Reactor Technology-- Components & Accessories
36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
ALLOYS
CARBON STEELS
CONTAINERS
FRACTURE PROPERTIES
IRON ALLOYS
IRON BASE ALLOYS
MECHANICAL PROPERTIES
PRESSURE VESSELS
REACTOR COMPONENTS
REACTOR MATERIALS
STEEL-ASTM-A302
STEEL-ASTM-A508
STEEL-ASTM-A533-B
STEELS