Blisk With Small Geometry Mistuning and Blend Repair: As-Measured Finite Element Model and Experimental Verification

Abstract

This paper presents an “As-Measured Model” (AMM) of a blended blisk, built upon the measurement of the true geometry of the blisk by the three-dimensional optical scanning technology. This high-fidelity model aims to account for the variances of blade frequencies and mode shapes within the real blisk in the presence of both the blend repair and inherent geometry mistuning due to manufacturing, etc. An improved mesh updating strategy is proposed to adapt a seed blisk finite element model (FEM) to the measured geometry. The resultant AMM is therefore able to accurately represent the measured blade-to-blade geometry variances. The classical blade detuning test (BDT) in combination with a novel “correction” procedure is employed to experimentally evaluate the “blade-alone” frequency mistuning pattern in the real blisk. Experimental verification of the AMM demonstrates that it is able to not only capture the blade-alone frequency and mode shape variations due to both the blend and intrinsic blade geometry variances, but also to reproduce the global dynamics of the blended blisk with acceptable accuracy.