| A bladed disk, such as a single stage of a turbomachinery rotor, is designed to be rotationally periodic. In reality, however, there are inevitably small differences between the blades, due to manufacturing tolerances, material defects, and uneven wear during use. These differences, known as mistuning, can cause a real bladed disk to have dramatically different dynamic behavior from that predicted for an ideal bladed disk with identical blades. Mistuning can cause localization of normal mode shapes and increases in maximum forced response vibration amplitudes. Accounting for the effects of mistuning during bladed disk design is difficult due to the fact that mistuning is random, and the mistuning present in any specific bladed disk is thus unknown. Recently developed computational techniques allow the efficient simulation of large numbers of mistuning patterns, providing the ability to predict the effects of mistuning in a statistical sense. While computational studies have given much insight into the occurrence of mistuning phenomena, and suggested possible design improvements such as intentionally mistuning the blades to avoid regimes of high mistuning sensitivity, the prediction of the response of a particular bladed disk still requires knowledge of its actual mistuning pattern.; This dissertation provides three significant contributions to the study of the dynamics of mistuned bladed disks. The first is an experimental validation of the computational techniques developed for efficient prediction of mistuned bladed disk behavior. The second is a set of methods for experimentally identifying the specific pattern of mistuning present in an actual bladed disk, using either free or forced response measurements. Third, this dissertation provides the first experimental demonstration of reduction in sensitivity to random mistuning due to the systematic introduction of intentional mistuning. Thus, the experimental studies presented here not only validate the accuracy of recent computational methods, but also confirm their utility in developing new design tools to avoid the negative consequences of mistuning. Furthermore, the mistuning identification techniques presented here allow more accurate prediction of the behavior of specific bladed disks and provide the ability to detect damage in existing bladed disks and monitor the mistuning present in newly manufactured specimens. |
