Material and Fatigue Induced Structural Instabilities of Corrugated Bellows at Low Temperatures

The corrugated bellows work often in extremely severe service conditions comprising temperature variations between ambient and operational level, high internal pressure, large cyclic axial offset and different types of misalignment offsets. This implies development and evolution of plastic strain fields in these components subjected to thermo-mechanical loads at low temperatures. The evolution of plastic strain fields is usually accompanied by two phenomena: ductile damage and strain induced martensitic transformation (already discussed in the previous chapters). Cryogenic temperatures catalyse the process of opening of micro-cracks and micro-voids shifting simultaneously deformations towards the elastic domain (considerable increase of yield strength). Nevertheless, the behaviour of corrugated bellows, highly optimised with respect to their size and stiffness, is affected by the low cycle fatigue phenomena.