The Maximum Factor by Which Forced Vibration of Blades Can Increase Due to Mistuning

In 1966 it was shown that the maximum factor by which the amplitude of forced vibration of blades can increase due to mistuning is, with certain assumptions, $1/2(1+N)$⁠, where N is the number of blades in the row. This report gives a further investigation of the circumstances when this factor can be obtained. These are small damping, and a relationship must hold between the mistuning distribution γ(s) and the interblade coupling function c(r), where r is the model number. The mistuning distribution must be symmetric about the blade on which maximum amplitude is to occur, s = 0. The coupling function must be symmetric about r = R, where R is the mode number of the excitation. If the coupling is purely mechanical, additional conditions apply. The coupling function c(r) must consist of a number of identical symmetric substrips. A 1976 result for mechanical coupling is amended.