NONLINEAR DYNAMICS ANALYSIS OF MISTUNED TURBINE BLADED DISKS WITH DAMPED SHROUDS

This paper deals with the real dynamics characteristics of a mistuned steam turbine bladed disk subjected to dry friction forces to better understand the nonlinear mistuning phenomenon. Normal load, which directly affects contact stiffness between interfaces, is chosen as the mistuning parameter. Based on Mindlin model, a forced response analysis of the finite element model of mistuned bladed disk with damped shrouds is performed in ANSYS. Compared with results of other simplified models, a real and complicated nonlinear behavior are observed here. A mass of qualitative analysis is also performed to assess the impact of the mistuning magnitude and excitation level on the vibration. The result shows that, vibration response of bladed disk is affected by excitation and mistuning level significantly. Local amplification " coefficient of vibration response in the cases of different mistuning levels is obtained by introducing 10 random mistuned patterns. In addition, frequency splitting phenomena even appears at one of the blades by the contribution of high mistuning levels. According to the calculated results for different excitation levels, the curve of modal damping varying with response amplitude is gained. Lastly, rigidity mistuning is introduced and a combined analysis is performed to investigate the influence of friction damping mistuning on rigidity mistuning in the same 10 random mistuning patterns. The arrangement of dry friction damping mistuning also could be controlled to reduce the local vibration amplification originating from structure mistuning. However, further statistical investigations should be made to gain more information. (CSPE)