Vibration Analysis of Rotor for Crack Identification

摘要

A theoretical and experimental dynamic analysis of a rotor-bearing system with a transversely cracked shaft is presented. To model the system for FEM analysis, a finite element for a cracked cylindrical shaft is developed. The additional flexibility due to the crack is evaluated from the linear fracture mechanics, using a breathing crack model derived in a rigorous way. A simplified opening/closing crack model is proposed to reduce the computational effort. The resulting parametrically excited system is nonlinear, and the equations of motion are solved using Hilbert, Hughes, and Taylor integration method (HHT) implemented in Matlab platform, where the stationary vibration caused by gravity and unbalance is analyzed. The results show that for half the first critical speed, the super-harmonic 2 * Ω and the typical orbit provide good indices for crack detection in rotating shafts.