Process Flow for Integrally Bladed Rotor Mistuning Identification During Depot Inspections Using Geometric Mistuning Approaches

Abstract Integrally Bladed Rotors (IBRs) are subject to foreign object damage, wear and tear, and repair processes that may mistune the system through nonuniform geometric perturbations during usage. This mistuning can drastically change an IBR's dynamic characteristics that manifest as increased forced responses and, subsequently, fatigue and failure at unscheduled maintenance intervals. To ensure fleet safety, IBRs routinely go through bench-level testing during engine depot visits. A bench-level process is presented here for inspections to continue part safety while learning more about the dynamic characteristics for the fleet. This process starts with optically scanning an IBR to obtain the geometric mistuning features. Mesh metamorphosis algorithms then alter a seed mesh of the design-intent part geometries to the as-measured part. Sector frequency deviations can be computed directly from finite element models (FEMs) of the morphed mesh. Accuracy of these deviations can then be assessed through mistuning identification via geometric mistuning reduced-order models (ROMs) combined with bench-level traveling wave excitation (TWE). These geometric mistuning methods can incorporate the effects of geometric mistuning, but also capture frequency shifts occurring from sources not captured by an optical scanner, e.g., material mistuning. Models resulting from this process stay connected to physics-based FEMs, which is highly desirable for other downstream analyses beyond frequency deviation calculations, e.g., stress and strain calculations. The proposed process is demonstrated on an industrial IBR and illustrates the proposed flow with comparisons between mistuning from geometric and other sources.