Elevated Temperature Fatigue Tests and Inelastic Stress Analysis of Bellows

For a multiwalled piping of the elevated temperature helium gas loop or HTR, some kinds of joints are required to absorb the thermal expansion difference between the inner and outer pipes. Bellows joints are planned to use for them and developed bellows. From the 900 deg C fatigue tests of the bellows, a design curve was obtained for the estimation of the allowable cycle versus the bellows deflection. Further, an inelastic analysis was carried out on the same figures by using a FEM code and tried to study the integrity of the bellows in accordance with the creep and fatigue interaction equations.