Numerical and experimental estimation of creep-fatigue life of Inconel 625 bellows at 570°C

摘要

Methodology for creep-fatigue design of bellows is not covered in design codes such as Expansion Joint Manufacturer's Association (EJMA). This paper presents the analysis and experimental validation of the creep-fatigue design of Inconel-625 bellows at 570°C. Creep-fatigue testing of the bellows was carried out in INSTRON servo electrical fatigue testing system, which is used in general for testing of cylindrical specimens for fatigue loading. Conceptual design and manufacturing of the bellows creep-fatigue testing specimen were carried out. Testing of the bellows was carried out at 3bar pressure and ±10mm movement at 570°C. Finite element analysis of the bellows was carried out using both linear elastic and inelastic approaches. The method suggested in RCC-MR was used for creep-fatigue design of the bellows using LE analysis. Chaboche and Rousselier visco-plastic constitutive model was used for inelastic analysis of the bellows. It was found that the design by analysis was conservative.