The influence of cracks in rotating shafts

Abstract

In this paper, the influence of transverse cracks in a rotating shaft is analyzed. 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 non-linear behaviour of the rotor system rapidly and efficiently by modeling 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.

A cracked beam finite element for rotating shaft dynamics and stability analysis

“…These works such as those of Darpe et al [2004], those of Jun et al [1992] and those of Sinou and Lees [2005; where we find numerical and experimental results of their investigations on certain aforementioned points remain faithful to the theoretical principles formalized in the 70s in some reference papers. In the other hand, remarkable and continuous progress of the computational tools allows the realization of successful three-dimensional models.…”

Implementation of a cohesive zone model for the investigation of the dynamic behavior of a rotating shaft with a transverse crack

“…The geometric functions that are used to describe the strain energy density, are not accurate enough, due to the fact that the crack passes from stress state caused by the vertical moment to that of horizontal moment [1]. The second approach is based on a theoretical model of a transverse crack, by reducing the second moment of area of the element at the location of the crack, then the opening and closing of the crack may be approximated by a cosine function [4][5]. An alternate method, based on a cohesive zone to model the dynamics of cracked rotor, will be discussed in this paper.…”

Rigid finite element model of a cracked rotor

“…The change in this parameter during one revolution can be interpreted as the well known crack steering function, reported in [5,6,14], and others. Fig.…”

“…In fact such dependency is nonlinear, as the stiffness depends on the cross sectional area and on the area moment of inertia of the uncracked segment. To improve the accuracy, the more exact assumptions can be taken, as explained in Appendix C. For the details the reader is referenced to [6,29].…”