Reduced-Order Model Construction Procedure for Robust Mistuning Identification of Blisks

Abstract

The reduced-order modeling of integrally bladed disks (blisks) for predicting the mistuned vibration response has been well studied and understood. For solving a direct vibration problem, adding modes to the modeling basis improves the accuracy of the reducedorder model (ROM) with respect to the parent nite element model. In contrast, when solving an inverse problem for system identication, adding modes to the ROM while using the same measurements may actually reduce its accuracy. This is especially true for solving inverse problems related to identication of blade mistuning parameters, because the characteristics of the selected system modes for the ROM may not match well the assumptions used in the mistuning modeling approach. In this work, a procedure is introduced for constructing a ROM referred to as the inverse ROM (IROM) that is well suited for solving the mistuning identication inverse problem. First, a quantitative metric is dened to characterize and rank the tuned system modes with respect to their suitability for constructing IROMs. Then, the direct problem is solved using a larger direct ROM (or DROM) with prescribed mistuning in order to interrogate and validate the performance of various IROMs as modes are added. This enables the automated construction of suitable IROMs and improves the overall accuracy and robustness of mistuning identication.