Static Frequency Test and Leaf Fracture Analysis of Turbine Blades in a Power Plant

Abstract

During the overhaul of a steam turbine of a power station, the frequency of the last twostages of the low-pressure rotor is tested and high-pressure rotor-regulated stage broken blades weresubjected to macroscopic inspection and analysis, chemical composition analysis, hardness test andmetallographic microstructure observation and analysis.The results of blade frequency measurementshow that the two stages of the low-pressure rotor can be safely and stably operated at the workingspeed. The results of broken blade analysis show that: due to the surface damage in the innersurface of the blade root, the blade vibration is aggravated, and the lower step of the concavegroove of the blade root is the stress concentration zone, where the fatigue crack source is generatedand gradually expanded, resulting in fatigue fracture of the blade; The fracture fatigue source zoneand the fatigue crack growth zone occupy approximately two-thirds of the entire fracture area,indicating that the blade fracture is a high-cycle fatigue fracture.