Estimating the effect of Manufacturing Variability on Turbine Blade Life

The life of turbine blades is central to the integrity of an aircraft engine. Turbine blades, when manufactured, inevitably exhibit some deviations in shape from the desired design specifications due to the influence of manufacturing variability. This manufacturing variability may in turn lead to variations in the expected life and performance of these blades. It becomes important therefore to understand and model the effect of manufacturing variability on turbine blade life. The present work proposes a methodology which employs an existing geometry manipulation technique, namely Free Form Deformation (FFD), to generate 3-d models of the probable manufactured blade shapes. FFD is employed in conjunction with optimization for morphing the base geometry to generate different probable manufactured blade shapes in a case where a limited number of measurements are available per blade to characterize these differences. Lifing estimations on these perturbed geometries show that the presence of variability due to manufacturing processes may result in a reduction of around 1.6% in mean life relative to the designed life, and, a maximum relative reduction of around 3.6%, for turbine blades manufactured over a span of one year.

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