THERMAL FATIGUE EVALUATION BASED ON THE METHODS FOR STRUCTURAL STRESS DETERMINATION ACCORDING TO EN 13445-3 ANNEX NA-COMPARISON WITH OTHER CODES

摘要

The European Pressure Vessel Standard EN 13445 provides in its part 3 (Design) a simplified method (Clause 17) and a detailed method for fatigue assessment (Clause 18) of unwelded and welded components. Clause 18 "Detailed Assessment of Fatigue Life" is under principal revision within the framework of the European working group "CEN/TC 54/WG 53 - Design methods" in order to reach a significant increase in user-friendliness and a clear guideline for the application. This paper is focused on the new recommendations for the thermal fatigue evaluation given in the new informative annex NA "Instructions for structural stress oriented finite element analyses using brick and shell elements". In this annex NA different application methods for the determination of structural stresses are explained in connection with the requirements for finite element models and analyses. This paper will give a short overview of the proposed approaches of structural stress determination in the new draft annex NA of the revised EN 13445-3 with special recommendations for thermal fatigue evaluation application. This constitutes an extension of the usual and established application of the structural stress approach for welds subjected to mechanical loading conditions. It will present the current state of the approaches based on the results of fatigue analyses according to EN 13445-3 Clause 18 for two different application examples. For validation purposes, these different approaches are compared with the results of Clause 17 of the EN 13445 and other pressure vessel design codes.