Mistuning identification in a bladed disk using wavelet packet transform

The dynamic response of a bladed disk is very sensitive to the symmetry of identical blades. If the properties of one or more blades vary slightly then the response can increase substantially, which is known as mistuning. Mistuning in bladed disks due to manufacturing tolerances has been extensively studied, with emphasis on response and fatigue life prediction. Damage to blades can also cause mistuning but has received only limited attention. The identification of mistuning in rotating bladed disks is a challenging and an on-going topic of investigation. This study proposes a Wavelet Energy-Based Mistuning Index (WEBMI) which is obtained from the wavelet packet transforms of both tuned and mistuned blade responses, and requires only output response signals. The proposed mistuning index is demonstrated on a lumped parameter model of a bladed disk, and mistuning was represented by altering the stiffness or mass of individual blades. Mistuning to single and multiple blades with different locations and severities was simulated. Gaussian white noise was added to the response signal to test robustness. Finally, experiments were conducted to validate the feasibility of the proposed method. The results demonstrate that the WEBMI is sensitive enough to identify subtle mistuning as small as 0.5% in single and multiple locations. Furthermore, the mistuning index increases monotonically with increases in mistuning severity.