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Description / Abstract:
INTRODUCTION
STP-NU-018 [3] investigated existing creep-fatigue rules to
improve the provisions on creep-fatigue evaluation of Mod.9Cr-1Mo
steel in Subsection NH of ASME Boiler and Pressure Vessel Code
Section III [1]. All the rules investigated were based on the time
fraction rules.
This report investigates newly proposed creep-fatigue evaluation
methods that have not been employed in exiting codes and
procedures, using the data on Mod.9Cr-1Mo steel collected in STPNU-
018 [3]. This report selected the following five promising methods,
all of which are more or less different from the conventional time
fraction method, for the investigation:
- Modified Ductility Exhaustion Method (MDEM)
- Strain Range Separation Method (SRSM)
- Approach for Pressure Vessel Applications (APVA)
- Hybrid Method of Time Fraction and Ductility Exhaustion
(Hybrid)
- Simplified Model Approach (SMT)
This report describes the outline and the predictability of
experimental results of the above methods, potential to deploying
the methods to NH is investigated from the viewpoints of required
database, extrapolation strategy and applicability to structural
design which is more complex than predicting material test results.
Also mentioned is the impact to the provisions of Subsection NH
when these methods were to be implemented replacing the current
provisions.
This report deals with Mod.9Cr-1Mo steel only. However, it is to
be noted that other materials such as 316 stainless steels
including low-carbon nitrogen added versions and Alloy 800H are
also of interest for the development of New Generation Nuclear
Plants.