Fretting fatigue crack analysis of the turbine blade from nuclear power plant

Abstract

The root cause of the failure of a cracked blade in the low pressure turbine of a nuclear power plant was investigated. The low clearance between the blade and the disk caused a sliding motion, which led to fretting wear during in-service operations. The crack in the blade was determined to have initiated under fretting wear and propagated with high cycle fatigue by means of analyzing the fracture surface of the failed blade. Micro oxide particles were detected from the Electron Dispersive Spectroscopy data analysis at the fatigue initiation position as typical evidence of fretting wear. The stress distribution on the blade in normal service was calculated with a non-linear elastic–plastic finite element method. The analysis results show that the crack initiation location was different with the location of the highest Mises stress. The fretting fatigue crack initiated under a combination of fretting wear and relatively high Mises stress. Designed fretting fatigue experiments were performed with the results that the fatigue life was greatly reduced by the interaction of the loading history and local fretting wear.