Single crystal nickel-based turbine blades are directionally solidified during the casting process with the crystallographic direction  aligned with the blade stacking axis. This alignment is usually controlled within 10 deg, known as the Primary angle. The rotation of the single crystal about the  axis is generally not controlled and this is known as the Secondary angle. The variation in Primary and Secondary angles relative to the blade geometry means that the stress response from blade to blade will be different, even for the same loading conditions. This paper investigates the influence of single crystal orientation on the elastic stresses of a CMSX-4 turbine blade root attachment using finite element analysis. The results demonstrate an appreciable variation in elastic stress when analyzed over the controlled Primary angle, and are further compounded by the uncontrolled Secondary angle. The maximum stress range will have a direct impact on the fatigue resistance of the turbine blade. By optimizing the Secondary angle variation the elastic stresses can be reduced, giving the potential to enhance the fatigue resistance of the turbine blade.
The Influence of Crystal Orientation on the Elastic Stresses of a Single Crystal Nickel-Based Turbine Blade
Savage, M. W. R. (October 27, 2011). "The Influence of Crystal Orientation on the Elastic Stresses of a Single Crystal Nickel-Based Turbine Blade." ASME. J. Eng. Gas Turbines Power. January 2012; 134(1): 012501. https://doi.org/10.1115/1.4004129
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