Fatigue test of piping bellows

not registered; not registered; Tsukimori, Kazuyuki*

The development of piping bellows as one of the cost reduction measures for Large FBR plants has been conducted in the Power Reactor and Nuclear Fuel Development Corporation since 1984. Fatigue and creep-fatigue strength evaluation is an important issue in practical application of bellows to the primary piping systems of FBR. This is the first report of a series of the fatigue and creep-fatigue tests for 42 inches diameter bellows. Fatigue tests described in this report were conducted on type 316 Stainless steel U-shaped bellows with seven convolutions at room temperature and 600 C. Through the present tests and analytical studies, the following conclusions were obtained. (1)Many of fatigue cracks distribute on the root surfaces near the both sides of bellows and they are almost intergranular fracture. (2)Fundamental characteristics of bellows in elastic region such as spring and strain response can be properly estimated by EJMA standards and FEM analysis. (3)Fatigue life of bellows can be properly estimated by material based fatigue life prediction using measured strains of bellows. (4)Maximum actual strain ranges can be reasonably estimated by using the elastic nominal strain range multiplied by the inelastic amplification factor per convolution (f f) and the factor (f) caused by stiffness fluctuation between convolutions. The effectiveness of the practical evaluation of strain range and fatigue life of bellows has been validated through this study.