Identification of Mistuning Based on Forced Response Measurements and Assessment for a Real Compressor Blisk

Abstract

We develop a novel method for the identification of mistuned blisks. The method relies on forced response measurements in a certain target frequency band. Modal stiffness deviations and an overall structural damping coefficient are obtained using a least-squares fit, fully consistent with a component-mode-based reduced-order model. To achieve a high frequency resolution in a very short test, we carry out rapid frequency sweeps and use a noise-robust, wavelet-based estimation of the steady-state response. The forcing is eliminated from the equations governing the mistuning parameters, and it is identified separately to reconstruct the forced response if requested. We first validate the method numerically and then apply it experimentally to a compressor blisk with an alternating (B-A) mistuning pattern. While most previous works on mistuning identification are limited to the lowest 1-2 mode families, we assess the method for the seventh (1C) and eighth (3T) mode family. Measured and reconstructed frequency responses are in good to very good agreement. We conclude that the developed method is useful to obtain high-quality estimates of mistuning parameters, which can then be used for vibration prediction.