Creep-fatigue lifetime modelling of bellows made of AISI 316 using advanced models

Expansion joints including metallic bellows are used in plant piping systems in order to accommodate thermal strains. Thus, many bellows are subjected to creep-fatigue loading due to start-up and shut-down. The present paper presents finite element simulations to recalculate component tests on small scale bellows made of AISI 316 with hold times up to 120 minutes at a temperature of 600 °C performed by Tsukimori et al. [1]. Therefor an Abaqus Standard deformation model and a fracture mechanics based lifetime model developed at Fraunhofer IWM have been used. The deformation model was adjusted to complex low cycle fatigue tests, low cycle fatigue tests with hold times and low cycle fatigue tests followed by relaxation tests performed at Fraunhofer IWM. The lifetime model was adjusted to creep-fatigue lifetime data from the literature. Steady state stress vs. strain hysteresis loops are required, but typically not published in literature. Thus, they were computed using the adjusted deformation model. The fracture mechanics based lifetime model is able to describe creep-fatigue data with hold times from few seconds up to 1000 minutes available from literature within a scatter band of factor 3. The influence of hold time on the bellows lifetime in the small scale tests performed by [1] could be reasonably predicted using the adjusted models.