The influence of cracks in rotating shafts

TL;DR

This paper investigates how transverse cracks affect the dynamic behavior of rotating shafts, focusing on modal property changes, crack breathing effects, and orbit evolution near resonance, with implications for online monitoring.

Contribution

It introduces an efficient method using Fourier series to model crack breathing and analyzes its impact on rotor dynamics, aiding crack detection and monitoring.

Findings

Cracks alter modal properties and dynamic response.

The Fourier series approach effectively models crack breathing.

Orbit features can indicate crack presence.

Abstract

In this paper, the influence of transverse cracks in a rotating shaft is analysed. The paper addresses the two distinct issues of the changes in modal properties and the influence of crack breathing on dynamic response during operation. Moreover, the evolution of the orbit of a cracked rotor near half of the first resonance frequency is investigated. The results provide a possible basis for an on-line monitoring system. In order to conduct this study, the dynamic response of a rotor with a breathing crack is evaluated by using the alternate frequency/time domain approach. It is shown that this method evaluates the nonlinear behaviour of the rotor system rapidly and efficiently by modelling the breathing crack with a truncated Fourier series. The dynamic response obtained by applying this method is compared with that evaluated through numerical integration. The resulting orbit during transient operation is presented and some distinguishing features of a cracked rotor are examined.