Research On Circumferential Stability Of Thin Wall Metal Bellows Under External Pressure With Tensile Displacement

Metal bellows expansion joint is the flexible part used to absorb dimensional changes caused by thermal expansion or contraction or reduce vibration of a pipeline and equipments. It is currently used in various national economy sectors. However, it often occurs in use that the most common unstable forms of the metal bellows are column instability, in-plane instability and circumferential instability. Instability is detrimental to bellows performance in that it can greatly reduce both fatigue life and pressure capacity, even engenders tragedy.At the present time, many scholars engaged in research of the column instability and in-plane instability of the metal bellows, and acquired a lot of valuable achievement. When circumferential instability of the metal bellows researched, the metal bellows regarded as rigid body, its circumferential instability was calculated & verified, based on calculation theory of the cylinder under external pressure. However, the shortcoming of the method is it was not considered that the effect of axial displacement to circumferential instability.In order to improve reliability of metal bellows under external pressure, its circumferential stability is researched via instability tests and nonlinear finite element analysis, the main contents as follows:Some tests are performed, there are singleply metal bellows only withstand external pressure, only withstand tensile displacement and withstand external pressure with tensile displacement. In three cases, the deformation of the metal bellows are observed, strain data are measured. The results indicated that it is circumferential instability that the metal bellows under external pressure, which occur wave crest collapse.It is researched via test that the deformation of multiplies metal bellows under external pressure with tensile displacement. The results indicated that it is circumferential instability that the metal bellows under external pressure, which occur wave crest collapse.Based on the work above, it is studied in ANSYS software that the singleply and multiplies metal bellows under external pressure with tensile displacement. The deformation and the stress distribution are obtained after the metal bellows losed its stability. The results show that the stress data and stress distribution are accurate.Both tests and the ANSYS software analyse show that the thin wall metal...