Exploration of blade detuning tests for mistuning identification of blisks

Abstract

This paper presents a novel blade mistuning identification method based on blade detuning tests. Blade detuning tests consist of blade-by-blade impact testing in a blisk with detuning masses purposefully attached on all the blades except the one currently under test. Due to the quite simple test setup and implementation, the detuning tests enable to estimate the blade frequency mistuning pattern of the blisk with low experimental effort. However, it was proved that non-negligible residual inter-blade coupling is responsible for an inaccurate identification of the truly ‘blade-alone’ mistuning pattern from the blade detuning test results. Therefore, a novel mistuning identification method is herein proposed in order to improve the accuracy of the estimated mistuning pattern. This method fully exploits the blade detuning test results and includes the residual inter-blade coupling due to the mass detuning mechanism. The quantification and the introduction of the residual inter-blade coupling into the identification procedure leads to the determination of a more accurate ‘blade-alone’ frequency mistuning pattern. This novel mistuning identification method is firstly validated in a numerical test case and then applied to a real blisk test piece.