Review of fatigue design procedures for pressure vessels

When applying detailed fatigue analysis to welds in pressure vessels, desig ners encounter practical difficulties with the methods required by national standards such as ASME BPV Section Vm Div. 2, BS5500 and AS1210. This paper discusses the main fatigue design stress parameters, being: (a) the stress intensity range and (b) the principal stress range, and evaluate s these for their validity over the scope of fatigue conditions they are re quired to predict. It is concluded that a practical and conservative approach for a given weld detail is to calculate geometric stress parameters at the critical locatio n, evaluate and select the larger of the two parameters above, and to compa re this to a fatigue curve based on undressed welded specimens. It is furth er concluded that an additional fatigue strength reduction factor of 2 be s uperimposed when the principal stress direction changes significantly. (C) 2001 Published by Elsevier Science Ltd.