Fatigue behavior and mechanism of FV520B in very high cycle regime

Abstract

BACKGROUND: High cycle fatigue (HCF) and very high cycle fatigue (VHCF) induced by wake flow and other causes are the main failure modes of impellers which are the key component of centrifugal compressors. Research on the fatigue behavior and mechanism of impeller material in the VHCF regime is beneficial to fatigue design and the remanufacturing of impellers, and it also has important significance to ensure a long operation life of centrifugal compressors. OBJECTIVE: The VHCF behavior and mechanism of impeller material FV520B has been studied. METHODS: Fatigue tests were conducted on a Shimadzu USF-2000 at a resonance frequency of 20 kHz and room temperature in air ambient. The fractures were observed by SEM. RESULTS: For FV520B-I, the S–N curve continuously declined, and there was no fatigue limit. Most of cracks initiated from subsurface inclusions in the VHCF regime. For FV520B-S, the S–N curve was far below that of FV520B-I, and there was a conventional fatigue limit. CONCLUSIONS: The fatigue behavior and mechanism of FV520B-I and FV520B-S are very different and determined by heat treatments. Prediction of the fatigue life in the VHCF regime according to the Paris law is not ideal. A new method for prediction of the fatigue life in the VHCF regime should be developed.