Identification of Integrally Bladed Rotor (IBR) Damping

Due to funding and scheduling limitations, current testing for different IBR damping techniques and treatments has been forced to be accomplished simultaneously on a single IBR. Just like IBRs in service, the rotors are mistuned and the modal response is highly coupled. Mistuning refers to the fact that slight manufacturing differences cause each blade to have a different natural frequency – they are mistuned. Even very small amounts of mistuning can cause some blades to vibrate much more than others. Practically, every IBR is mistuned and even small amounts of mistuning can affect the frequency response of the IBR in a way that is currently indistinguishable from damping variations. Furthermore, different damping treatments change the frequencies of the blades as well as their damping. As a result, there are currently no accurate, reliable methods for extracting the individual damping contributions of each blade from the vibratory response of an IBR. The purpose of the work proposed here is to develop such methods.