Fatigue strength of smooth and notched specimens of ASME SA 106-B steel in PWR (pressurized water reactor) environments

Technical Report · Thu Sep 01 04:00:00 EDT 1988

OSTI ID:6815165

Terrell, J B

Fatigue strain-life tests were conducted on ASME SA 106-B piping steel base metal and weld metal specimens in 288/degree/C (550/degree/F) pressurized water reactor (PWR) environments as a function of strain amplitude, strain ratio, notch acuity, and cyclic frequency. Notched base metal specimens tested at 0.017 Hz in 1.0 part per billion (ppB) dissolved oxygen environments nearly completely used up the margins of safety of 2 on stress and 20 on cycles incorporated into the ASME Section III design curve for carbon steels, whereas smooth specimen tests from base and weld metal under similar conditions showed considerably less degradation. Tests conducted with specimens having theoretical notch concentration (K/sub t/) values ranging from 2 to 6 showed virtually no effect of notch acuity on fatigue life. Tests conducted with smooth base and weld metal specimens at 1.0 Hz showed virtually no degradation in cycles to failure when compared to 288/degree/C air test results. In all cases, however, the effect of temperature alone reduces the margin of safety offered by the design curve in the low cycle regime for the test specimens. Comparison between the fatigue life results of smooth and notched specimens suggests that fatigue crack initiation is not significantly affected by 1.0 ppB dissolved oxygen, and that most of the observed degradation may be attributed to crack growth acceleration. These results suggest that the ASME Section III methodology should be revised to account for PWR environment variables which degrade fatigue life of pressure-retaining components. 48 refs., 42 figs.

• Research Organization: Nuclear Regulatory Commission, Washington, DC (USA). Div. of Engineering; Materials Engineering Associates, Inc., Lanham, MD (USA)
• OSTI ID: 6815165
• Report Number(s): NUREG/CR-5136; MEA-2289; ON: TI89001019
• Country of Publication: United States
• Language: English

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