Establishing blend repair limit of blisks –from a perspective of vibration amplification
Efficient sustainment of the extremely expensive blisks in advanced aeroengines requires that damaged blades can be cost-effectively repaired by blending operations with high reliability. However, limited understanding of blending effects on the forced response of blisks challenges the rational determination of blend limits, i.e., the maximum allowable blend size, location and number in a damaged blisk. 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.

The project BRAVO aims to develop a comprehensive vibration evaluation tool for blended blisks and establish the repair philosophy on blend limits. By employing the state-of-the-art 3D optical geometry scanning technology, geometry variances due to both blends and intrinsic blade geometric deviations can be effectively accounted for. Major scientific advances include:
Novel deterministic methodologies of forced response analysis for blended blisks relying on the optically based as-measured model.
Holistic vibration evaluation of blended blisks by comparing the as-measured-model-based simulations, modal tests, bench test under traveling wave excitation and spinning rig tests.
Innovative probabilistic assessment for predictive evaluation of a population of possible blends and further determination of a tailored blend limit for a damaged blisk.

A highly interdisciplinary collaboration will benefit both the ER with extensive experience in bladed disk dynamics, and the supervisor possessing top-level research capability in blade vibration testing. With deepened competence in both technical and transferable skills, the ER will reach a high level of professional maturity and scientific independence as a group leader. 

Results will potentially exert a strong industrial impact for repair contractors, contributing to the competitiveness of European aviation industry.