Papers by Keyword: Cyclic Pressurization

Abstract: Study was attempted to produce stress-life curve of the zirconium tube under the cyclic pressurization and to analyze its behavior. The internal pressurization machine was devised and the low cycle fatigue test at the zirconium cladding tube was carried out. The result showed that the O’Donnell and Langer relationship can be fitted to the fatigue behavior of the zirconium cladding under the cyclic pressurization, where the fatigue limit of the Zircaloy-4 at 350oC was shown at 341.6MPa. From the analysis of the diametral changes and the fractographic observation, a combined creep-fatigue interaction rather than a pure fatigue had an influence on the failure of the zirconium cladding under the cyclic pressurization at 350oC.

Abstract: It is known that the basic mechanism of fatigue crack growth in ductile pressure vessel steels, which is repetitive blunting and re-sharpening of the crack tip, is a weak acoustic emission (AE) source. On the other hand, a large number of AE events occur during cyclic crack growth. Most AE events are caused by repetitive friction at the fracture surfaces, but these AE events show relatively weak correlation with the crack growth velocity. In the paper it is shown, based on examples – fatigue crack growth starting from an artificial weld defect, cycling of a natural crack defect, crack initiation and growth in gas cylinders - which information can be gained by relatively simple analyses of the AE data from cyclic pressure tests.