With Inelastic analyses requiring a substantially greater expenditure of effort over elastic analyses, there is strong incentive to establish an elastic design criterion for ratchetting that is not . excessively conservative and consequently restrictive.To establish the design curves for ratchetting, the ANSYS computer program was used to develop elastic-plastic-creep solutions for several cases of a long, sodium-filled pipe. The pipe was subjected to a fluid temperature history which consists of a rapid down-transient followed by a gradual rise to operating temperature, and a 500 hr. hold time at that temperature. The parameters of the analytical solutions covered the range of interest for sodium-cooled nuclear systems. The only material considered was 304 stainless steel.Design curves were developed for ratchet strain as a function of elastic primary and secondary stress intensities and temperature.The results of this study indicate that the existing design rules of FRA-152 rev. 3 and of the proposed LMEC revision to the ASME Code Case 1331-5 for loading cycles with long hold timti are very conservative, with one exception. That exception is rule A.2.1.2(4) of the proposed revision to the ASMS Code. When compared to the results of the study, the rule is consistently and reasonably conservative for all loadings and temperatures studied.
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