Abstract
This paper is concerned with the premature failures occurred in the high pressure compressor section of the gas turbine of HESA power plant in Iran. Metallurgical and mechanical properties of the blade alloy were evaluated. Fractography investigations were carried out on the fracture surface of the blade roots using scanning electron microscopy. Stress and fracture simulations were conducted using ANSYS software in both 2D and 3D dimensions under centrifugal, aerodynamic and contact forces. The aerodynamic forces were evaluated using FLUENT software. The results showed no metallurgical and mechanical deviations for the blade material from standards. SEM fractography showed different aspects of fretting fatigue including multiple crack initiation sites, fatigue beach marks, debris particles, and a high surface roughness on the edge of contact (EOC). The simulation results showed that there was a high stress gradient at the EOC of the blade which is one of the most significant characteristics of the fretting fatigue. Another analysis was performed to simulate the fracture by creating an initial crack on the EOC. The stress fields and stress intensity factors for modes I, II and III were evaluated along the crack front. The results indicated a strong stress intensity factor for mode I at the EOC.
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