ASSESSMENT OF BEND FATIGUE TESTS USING RSE-M STRESS ANALYSIS TECHNIQUES AND THE ASME SECTION III FATIGUE DESIGN RULES

摘要

Preparing the scope and extent of components requiring inspections in industrial plant demands careful consideration given the commercial implications. Stress analysis can usefully be employed to ascertain whether pipework components should be inspected. This can be achieved by interpreting pipework loads whilst giving consideration to all relevant failure mechanisms. Moreover, due to the size of the components the use of stress analysis can provide a means of targeted inspections by identifying areas of high stress where material damage is most likely to be observed. This paper compares the findings of fatigue tests reported by MPA Stuttgart in the mid 1990s of pipework bends subjected to combined pressure and moment loading with calculated fatigue damage using an analytical approach which combines the RSE-M stress analysis methods with the ASME Division I Section III NB fatigue design rules. The comparison is of interest as it has been found that the combined use of RSE-M and the ASME Division I Section III NB fatigue damage rules provides good agreement of calculated stresses with the locations and orientation of crack initiation observed in the fatigue tests. The calculated ASME Division I Section III NB fatigue endurance was found to bound that determined for the tests by a reasonable margin. Therefore, this approach provides a powerful means of assessing the fatigue life of in-service bends and confirms that the use of these tools is appropriate.