Mistuning characteristics analysis of mistuned bladed disk assemblies

The problem of determining the worst mistuning pattern and robust maximum mistuned forced response of turbine engine bladed disks was presented and solved as an optimization problem.Maximum resonant amplitudes searched across all degrees of a mistuned bladed disk and across all excitation frequencies in a given range were combined into an objective function.Individual blade mistuning was controlled by varying mistuning parameters.This approach was exemplified by a lumped-parametric model with two-degree-of-freedom per blade disk sector.Results of the optimum search of the worst-case mistuning patterns for the lumped parameter model were analyzed,showing that maximum blade forced response in a mistuned bladed disk was associated with mistuning jump,causing strong localization of the vibration response in a particular blade.Detailed two-degree-of-freedom per blade disk model was also used for calculation of the maximum forced resonant response of mistuned assemblies and for determination of its sensitivity coefficients with respect to mistuning variation.Studies have shown that there is not a threshold of frequency mistuning beyond which the maximum forced response levels off,or even drops,as the degree of mistuning is increased with the tendency of the forced response amplification factor.