STATISTICAL ANALYSIS OF THE VIBRATION OF MISTUNED CENTRIFUGAL IMPELLERS WITH CRACK DAMAGE

摘要

Statistical analysis of the effects of random mistiming on the nonlinear vibration of a cracked impeller of centrifugal compressor is presented and used to calculate the statistical characteristics of the forced response and the distribution of frequencies. Based on a finite element model, a hybrid interface method of component mode synthesis (CMS) is employed to generate a reduced-order model (ROM) of the cracked impeller. The degrees of freedoms on the crack surfaces are retained in the ROM so that the crack breathing effects can be simulated. Random mistiming is modeled by introducing small variations in Young's modulus of each blade. Then, the resulting nonlinear equations are solved by applying multi-harmonic balance method. Probability distributions of the forced response and frequencies of the mistuned impeller are obtained by a numerical Monte Carlo simulation and are used to calculate means and standard deviations. The results show that as the crack length grows, resonant frequencies tend to decrease, which is a potential feature for crack detection.