Study on Stress and Strain for Fatigue Cumulation Evaluation in Turbine Generator Shafts Due to Torsional Vibration

摘要

The cracks emerged in a fossil-fired power plant in China in 2008 and several similar crack accidents had been detected in nuclear turbines in USA before. The possible causes of the cracks are analyzed in previous study while the torsional vibration is one of the most significant factors. The paper analyzes the impact of torsional vibration using the practical running data in some turbine generator unit. Based on the transient response analysis under emulational subsynchronous oscillation model simplified from the practical network, the torques acted on the coupling section are analyzed. Then the stress and strain field is calculated for local dangerous point search in Zone of Vulnerability (ZoV) and the fatigue damage criterion determination. Manson-Coffin equation is used to ascertain whether it is high-cycle fatigue or low-cycle fatigue and the fatigue data from standard test specimen is used. The method using local stress and strain analysis as well as fatigue damage cumulation study may establish a novel way to diagnose the crack in an early stage.