Life Estimate of a Compressor Blade through Fractography

Failure analysis of fractured components provides some information about the causes and conditions of fracture. Fractography is an indispensable part of the failure analysis as it is usually the only means by which the failure mechanism can be established. By using fractography, some information such as component's life, values of the stress intensity factor and the applied stress can be calculated. In this paper, the results of categorized investigations and tests such as chemical analysis and fractography of a failed compressor blade of a Frame 6 type gas turbine engine have been presented. The results showed that the source of initial cracks on the blade is corrosion pitting on the surface of the blade. The failure mechanism is high cycle fatigue. Crack growth rate has been calculated from striation spacing and has been compared with the numerical solution. The stress intensity factor range and the applied stress range have also been calculated and compared with numerical results. Fractographic analysis and numerical computations are consistent with each other.