Maximum Mistuned Vibration Amplitude With Aerodynamic Damping

Mistuning can dramatically increase the forced response of a bladed disk. In the case of damping coming from aerodynamic effects the situation is more complicated because the value of the damping is typically different for the different travelling wave modes of the system. This damping variability changes the effect of mistuning, and it can even result in a reduction of the maximum mistuned forced response amplitude below that of the tuned case (this was not possible in the usual case of constant material damping). In this paper the Asymptotic Mistuning Model (AMM) methodology is used to analyze this situation. The AMM is a reduced model that is systematically derived from the complete mistuned bladed disk dynamical model using a perturbative procedure based on the small size of the mistuning and the damping. Several different forcing cases are analyzed, and the results from the AMM are quantitatively compared with those from a FEM model of a mistuned bladed disk. The AMM gives also precise information about the key mechanisms involved in the forced response of mistuned cyclic structures, and about the maximum amplification of the vibration amplitude that the system can experience.