Numerical Study of Structural Change Estimation in a Rotor System Based on Changes in Resonance and Antiresonance Frequencies

摘要

A structural change quantification methodology is explored in which the magnitude and location of a structural alteration is identified in a rotor system. The proposed structural alterations may be interpreted as physical damage to a structure, in efforts of advancing structural health monitoring activities. The structural change quantification strategy involves the use of resonance and antiresonance frequencies which are collected from several transfer functions calculated from a finite element rotor model. These values are collected and included in an objective function which outputs an error value that is subsequently minimized. The resulting objective contains sufficient information to identify the dynamic characteristics of the rotor in both the frequency and spatial domains. A finite element model with carefully selected tunable parameters is iteratively adjusted using a numerical optimization algorithm to determine the source of the structural change. The numerical studies presented in this work utilize a generic rotor model with features such as a hollow shaft, two ball bearings, several disks, and multiple material layers. The method used for structural excitation is assumed to utilize magnetic actuators for nonintrusive operations. First, the investigations optimize the objective function using a hybrid optimization approach which applies both the NSGA-Ⅱ genetic and the Nelder-Mead optimization algorithms. The objective function is optimized to maximize the sensitivity of the rotor's finite elements to detect structural change. Second, a simulated local structural change is implemented in which the detection methodology is employed to locate. An investigation of the effect of error in the simulated data on the prediction's accuracy is addressed.