1989 Volume 38 Issue 427 Pages 430-436
In order to investigate the fatigue strength of bellows at elevated temperature, fatigue tests at room temperature and 500°C, and stress analyses have been conducted on the manufactured bellows. The manufactured bellows are a two-ply type, in which strain can be decreased by axial extension and compression without loss of stiffness against pressure.
It was found that the strain distribution changed with the bellows thickness and usually the maximum strain appeared at the outer surface of the root in the outer bellows. In order to estimate the fatigue lifetime of bellows, the octahedral shearing strain derived from both the axial and circumferential strains was found to be more effective than the estimation with only the axial strain, which is commonly used. Fatigue cracks were produced in the maximum strain area, and the cracks propagated from the outer surface to the inner surface of the bellows. It seems that the strain intensity factor obtained from the measured strain is effective for estimation of fatigue crack propagation rates.
