Fatigue Assessment of a Weld Joint Subjected to Thermal Stresses

Fatigue analysis is performed for a full-penetration weld joint, welded from both sides, connecting a cylindrical vessel to a flat head. It is subjected to a repeated transient cycle of ambient temperature inside the vessel. No pressure is cycled. Finite element heat transfer and elastic stress analyses are performed, and stress ranges are calculated. The allowable number of cycles for cyclic service is obtained by two structural stress methods. One is a method proposed for the ASME Boiler and Pressure Vessel code and the other is in the European Standard for unfired pressure vessels. It is found that for the same geometry and loading the former would permit 136,000 or 36,000 cycles while the latter would permit 8,000 cycles.