BRAVO · Establishing Blend Repair limit of blisks –from A perspective of Vibration amplificatiOn

Establishing Blend Repair limit of blisks –from A perspective of Vibration amplificatiOn

Blisks are extensively used in the fan/compressor sections of advanced aeroengines, due to their reduced-weight and increased-performance benefits. However, they also suffer from notorious disadvantages of technical difficulty and high cost arising from the repair process if inevitable blade damages in service occur, e.g., foreign object damages and wear, etc. Efficient sustainment of the extremely expensive blisks requires that damaged blades can be cost-effectively repaired by blending operations with high reliability. Structural dynamics evaluations for the repaired blisks are of significant importance to ensure continued safe operation with minimal risk of failure. However, currently limited understanding of blending effects on the structural dynamics of blisks challenges the rational determination of blend limits, i.e., the maximum allowable blend size, location and number in a damaged blisk. One of the principal reasons is that blisks are susceptible to high-level blade vibration due to inevitable blade mistuning. Blade mistuning arises primarily from the scatters of blade geometry profiles due to manufacturing tolerance. Moreover, blend repairs of the blades during maintenance can also induce relatively large geometry variances. The underlying fundamental issue is whether or not the blends will exacerbate the intrinsic geometric mistuning such that the blisk is subject to excessive vibration level and fails from high cycle fatigue. In fact, the accurate modelling and dynamic analysis of geometrically mistuned blisks has been a long-standing issue in both the academic and industrial communities. In pursuit of an improved blade geometric mistuning evaluation capability, the BRAVO project focuses on development of the high-fidelity dynamic modeling, analysis and experimental verification techniques specifically for blisks with both intrinsic small geometry mistuning and blend repairs, based on the state-of-the-art 3D optical geometry scanning technology. The BRAVO project aims to develop a comprehensive vibration evaluation tool for industrial designers to predict the risks and benefits of possible blend repairs within damaged blisks. A parallel goal of the MSCA Individual Fellowship is to enhance the fellow’s professional maturity and scientific independence as a research group leader.

Data: CORDIS, © European Union