Paper Title
Fatigue Life Prediction of Steam Turbine Blades with Three-Dimensional Structural Mistuning

Abstract
Low-Pressure steam turbines commonly experience premature blade and disk failures due to stress concentrations at the blade root area of its bladed disk. Hence, inspired by such problems encountered with steam turbine blades, this research presents a numerical methodology for the life prediction of mistuned steam turbine blades caused by variations in blade geometry as such studies have not yet been contemplated. Steam turbine blades are typically subjected to steam flow bending, centrifugal loading, vibration and structural mistuning. Based on these factors, a simplified, scaled-down, steam turbine bladed disk model was developed using finite element software. Acquisition of the vibration characteristics and steady-state stress response of the disk models was performed through finite element analysis. Thereafter, numerical stress distributions were acquired, and the model was subsequently exported to Fe-Safe software for fatigue life calculations based on centrifugal and harmonic sinusoidal pressure loading. Subsequently, Monte Carlo simulations were performed in Companion software to determine the probabilistic fatigue life for 17 cases of steam turbine-bladed disks which was defined by selecting mistuning (geometry variation) percentages as the random variables. Thereafter, the obtained results were validated by the discrete results with a good level of correlation being achieved between them. The results showed that the fatigue life is most sensitive to changes in blade thickness, followed by its length, and then the width, in this order. Hence, the developed methodology was proven reliable and can be successfully used to predict the fatigue life of mistuned steam turbine blades. Keywords - Blade Geometric Variation, Turbine Blade Mistuning, Finite Element Analysis, Fatigue