A Perturbed Order-Reduction Method for Modal Analysis of 3-D Blade Disk with Mistuning

The high-cycle fatigue of mistuned blade disks caused by vibration localization has adverse effects on safety of the blades. A real blisk structure contains many details, so if FEM is used, the number of nodes in the mesh is so large that the modal computation efficiency is low. In order to solve this problem, a perturbed order-reduction method is proposed in this paper. Firstly, the blade disk's stiffness and mass matrixes are divided into two components: the tuned component and the mistuned component. Then, the mistuned component of the original structure is transformed into the corresponding change in the order-reduced structure by using coordinate order-reduction transformation relationship in the fixed interface modal synthesis method. The coordinated modal information is repeatedly used by the perturbation method. The solution of mistuned blade disk modal is transformed into the product of tuning matrix and mistuning matrix, and the natural frequencies and modals of blade disk under mistuned distribution are calculated efficiently. A Rotor 67 compressor blade disk is taken as the calculating example, and the computation results show that the frequency calculation error of the perturbed order-reduction method is less than 0.3% and the modal displacement calculation error is less than 0.25%. The modal calculation time of the perturbed order-reduction method is 30% that of the conventional order-reduction method. It is concluded that this method can greatly improve the efficiency of modal calculation of mistuned blade disk under the requirement of engineering calculation accuracy. © 2019, Editorial Office of Journal of Xi'an Jiaotong University. All right reserved.