Study on Vibration Characteristics of Single Crystal Blade and Directionally Solidified Blade

In modern gas turbines, SC (Single Crystal) and DS (Directionally Solidified) nickel alloys are applied which, compared to CC (Conventionally Casting) alloys, hold a higher cyclic life and a significantly improved creep rupture strength. Because SC and DS alloys feature a significant directionally dependence of material properties, the vibration analysis of the SC and DS blade has to be carried out, taking account of the anisotropy of material properties. In the vibration analysis by FEA (Finite Element Analysis), the DS blade has to be modeled approximately as transverse orthotropic material, while the SC blade can be modeled exactly as orthotropic material in lattice directions. In order to design the SC and DS blade with high reliability, it is necessary to establish the analysis model and to clarify the influence of the anisotropy of the material properties on the vibration characteristics of the blade. In this paper, first, the effect of the anisotropy of elastic constants on the vibration characteristics of the SC and DS blade is investigated. Second, the validity of the assumption of the transverse isotropy for the DS blade, which is applied in the current blade design, is examined by Monte Carlo simulation. Finally, the frequency deviation of the SC and DS blade is analyzed by the sensitivity analysis method, and is compared to that of the CC blade.