Fatigue of bellows, a new design approach

Abstract

Consideration of fatigue is generally an important aspect of the design of metallic bellows expansion joints. These components are subject to displacement loading which frequently results in cyclic strains well beyond the proportional limit for the material. At these high-strain levels, plastic strian concentration occurs. Current design practice relies on use of empirical fatigue curves based on bellows testing. Prediction of fatigue behavior based on the combination of analysis and polished bar fatigue data is not considered to be reliable. One of the reasons for the unreliability is plastic strain concentration. It is shown that the difference between bellows and polished bar fatigue behavior, as well as the difference between reinforced and unreinforced bellows, can be largerly attributed to this strain concentration. Further, it is shown that fatigue life of bellows can be better predicted by partitioning the bellows fatigue data based on a geometry parameter. © 2001 Elsevier Science Ltd. All rights reserved.