Aerodynamic/Structural Mistuning Technologies for Assessing IBR/Blisk Repairs

New technologies for assessing how blending affects structural and aerodynamic mistuning will be developed using the combined strengths of Blade Diagnostics Corporation and Duke University. BDC has developed an approach for identifying aerodynamic mistuning from engine data that will be further developed under this STTR. Duke will develop new methods for computing the effect of blending on the aerodynamic damping and excitation forces that act on blended blades. The accuracy of Duke's method will be assessed using the BDC aerodynamic mistuning identification software and benchmark data provided by GE Aircraft Engines. Consequently, at the end of this STTR we will have demonstrated that we can use the BDC software to process NSMS data and extract information about the excitation forces and damping that act on individual blades, and that we can use the new Duke University CFD codes to predict how changes in the blades geometry from blending affects the aerodynamic forces and damping that acts on the blade. These tools will be integrated into a mistuning inspection machine (MIM) that BDC is developing for the Air Force. The MIM can then assess how blending a blade affects the likelihood of HCF failure when the Blisk is in the engine. BENEFITS: Blade Diagnostics Corporation will integrate the aerodynamic mistuning capability, developed in this STTR with their Mistuning Inspection Machine (MIM) being developed for the Air Force) so that the effect of aerodynamic mistuning as well as structural mistuning will be taken into account when calculating how blending a particular blade will affect the vibratory response of the IBR/Blisk when it is put back into service. In effect, the added aerodynamic capability developed in this STTR will transform BDC's MIM into a virtual engine test for blended blades. Consequently, at the end of this effort a validated technology will be in place that will allow the DoD to use relatively low cost blending operations to repair a larger number of IBRs/Blisks while reducing the likelihood of HCF failure from mistuning. This capability fits directly with the R&D goals of the DoD's VAATE program (Versatile Affordable Advanced Turbine Engines) as well as the more recently launched Propulsion Safety and Affordable Readiness (P-SAR) initiative. Looking at the future from the opposite viewpoint, an IBR/Blisk-laden world without the described capability would mean a large number of damaged components ($100K to $500K each) that can't be returned to service or that need to be repaired using alternative processes that are much more expensive, e.g. blade replacement. Clearly, fleet readiness would be adversely affected. The proposed effort thus offers a capability that is both timely and appropriate. With GE Aircraft Engines as an active participant in the program, there is every expectation that the capability developed in the STTR will be promptly transitioned to manufacturing and operational service to meet what are already important Air Force and Navy needs. In addition to meeting important DoD needs for cost effective repairs, it should also be noted that the latest models of commercial aircraft engines are also using IBRs/Blisks. As a result, the proposed new technology has dual use application to commercial as well as military engines.