Theoretical Modeling of Creep Behavior of Bellows and Some Applications

The use of bellows expansion joints is an effective method to rationalize various piping systems in industry. In the structural design, the requirements for preventing failures such as ratcheting, fatigue, and buckling should be satisfied. The mechanisms of some failure modes of bellows are different from those of vessels and piping components, which makes it difficult to estimate the behaviors. In the case of high-temperature operation, creep behavior of bellows should be considered. In this paper, a simplified theoretical modeling of creep behavior of bellows is presented. The formulation is developed by using Norton’s law for creep property of bellows material and assuming meridional bending stress is dominant. According to this modeling, bellows convolution dimensions are considered directly. The excessive creep deformation problem of bellows under internal pressure and the elastic follow-up behavior problem of a piping system with bellows expansion joints are examined as the applications of this modeling. The results are compared with detailed analysis results by FEM, and the applicability and the validity of this modeling is discussed.