During the past 30 years the main rules for fatigue analysis of pressure vessels were based on elastic approaches in order to evaluate a cyclic strain amplitude and compare with an S-N fatigue curve for the corresponding material. After review of some rules in different Nuclear and Non Nuclear Codes, like ASME Boiler & Pressure Vessel Code Section III, French RCC-M and RCC-MRx, European Standards EN 13445, the major conservatisms and uncertainties of different rules are discussed.
All these Codes propose simple rules to evaluate the strain amplitude based on elastic approaches and simplified correction factors (Ke and Kv), transient combination rules and damage cumulating procedure.
In the other hand, the material properties are based on standard fatigue tests done on the material associated to reduction factors to consider some particular effects like scatter, scale, surface roughness, mean stress or environmental effects to transfer them from small specimen to real structures.
Concerned components are mainly piping systems.
No existing Code covers all the aspects of fatigue with similar conservatisms that can affect the in-service inspection programs and the remaining life assessment of the corresponding components.
After the review of different rules, key factors that affect the results and predictions will be identified.
Some proposals will be issued to progress in the near future. Finally, a first set of recommendation on fatigue analysis will be presented to improve existing codes on an harmonized way, associated to material properties needed, as fatigue curves associated to reduction factors.
