Measurement Point Selection and Modal Damping Identification for Bladed Disks

Abstract

A novel measurement point selection (MPS) technique for bladed disks (blisks) is presented and applied to a new modal damping identification method. When gathering data to be used for applications such as mistuning identification in blisks, it is important to measure points which provide sufficient and accurate information for the analysis. However, to reduce the experimental time and cost, the measurement points should be chosen optimally so that the minimum number of measurements have to be collected. This paper discusses a modified form of the effective independence distribution vector (EIDV) method presented by Penny et al. and adapted by Holland et al. The key novel aspect of the proposed method is that it uses only single sector-level calculations instead of the whole system. A residual weighting optimizes the MPS technique for noisy measurements. The method presented is equivalent to the full system EIDV method, but it decreases the computational cost, increases the robustness of the identification, and minimizes the measurement time. Also, a novel method to identify damping parameters for each mode in a frequency range of interest is presented. This method utilizes the proposed MPS technique to increase the accuracy of the identification. Measurement locations and modal damping results for a 30 degree of freedom system and a blisk with a complex geometry are presented. Using the proposed methodologies it is possible to obtain an accurate modal damping identification with a decreased computational and measurement cost.