There were no fatigue crack growth rate factors (C, m) and fatigue crack growth threshold of stress intensity range for carbon and low alloy steels with yield strength less than or equal to 620 MPa in Table KD-430 and KD-430M of ASME Section VIII Division 3 (hereinafter called ASME Div.3). These fatigue crack growth rate factors and fatigue crack growth threshold of stress intensity factor range for intermediate strength ferritic steels were also necessary for design of ASME Div.3 vessels. The fatigue crack growth rates given in API-579-1/ ASME FFS-1, ASME Sec. XI, reported in Bloom’s paper and the crack growth rates for high strength low alloy steels given in ASME Div.3 were investigated. An equation of fatigue crack growth corrected by stress intensity factor ratio was developed based on the investigation. The developed equation of fatigue crack growth was confirmed to agree with the test data in Bloom’s paper for negative and positive R ratio. Hence this equation, which was appropriate for wide range of positive and negative R ratio, was proposed for ASME Div.3. The addition of fatigue crack growth threshold of stress intensity factor range for intermediate strength ferritic steels was also proposed. The fatigue crack growth rate factors at room temperature were provided in Table KD-430 and KD-430M. As the operating temperature is higher than room temperature, the temperature correction is necessary for fatigue crack growth calculation. The temperature correction method in KD-4 was also proposed. These proposed changes were approved by Board in 2018. The background of these proposed changes was shown in this paper.

Background of Addition of Fatigue Crack Growth Rate Factors for Intermediate Strength Ferritic Steels in KD-4 of ASME Section VIII Division 3

Paper Proceedings: https://asmedigitalcollection.asme.org/PVP/PVP2021/volume/85314

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