Probabilistic Risk Assessment for Life Extension of Turbine Engine Rotors

Maintaining the component service life beyond its historical limits requires the ability to accurately quantify component reliability and address the uncertainties in material responses. A probabilistic method for predicting the total fatigue life was developed and applied to determine the probability of failure of a Ti-6Al-4V turbine disk component. The total fatigue life incorporates a dual mechanism approach including the crack initiation life and propagation life while simultaneously determining the associated initial flaw sizes. A microstructure-based model was employed to address the uncertainties in material response and relate the crack initiation life with crack size. The propagation life was characterized using both small and large crack growth models to ensure accurate fatigue life prediction. Fatigue life predictions were found to correlate with experimental data at high stress levels. The risk assessment can be used to estimate the expected initial crack sizes from variability in material properties, which can further be used to establish an enhanced inspection planning.

Automated summary

Accurately evaluating reliability and addressing uncertainties in material response are crucial for extending the service life of components beyond historical limits. A probabilistic method has been developed and applied to predict the total fatigue life of a Ti-6Al-4V turbine disk component, taking into account both crack initiation and propagation mechanisms, as well as considering the uncertainties in material response using a microstructure-based model. The predictions of fatigue life have been validated against experimental data, particularly at high stress levels, and the risk assessment can be used to estimate initial crack sizes for enhanced inspection planning.