ABSTRACT
It is clear that an accurate analytical model is still absent, which considers the coupling influence of both crack location and unbalance force on the crack breathing mechanism. This paper aims to develop an unbalanced shaft model to study the effect of crack location on the breathing behaviour
1 INTRODUCTION
In rotating machinery, breathing of the fatigue cracks are considered to be one of the main rotor faults. It has a great deal of attention in literature as one of the main causes of dangerous damages in rotor systems (Georgantzinos & Anifantis, 2008). From the last decade alone a wide variety of analytical and practical methods have been used or developed for the detection of transverse rotor cracks (Kulesza, 2014; Ming et al., 2013; Yan et al., 2013). Some papers on cracked shaft literature used gaping crack models where the crack is considered to always be fully open (Dimarogonas & Papadopoulos, 1983; Papadopoulos & Dimarogonas, 1987). However, such a model does not represent the actual breathing of a fatigue crack. Improvements on the non-linear nature of crack breathing are seen through a switching crack model (Sekhar, 2003; Sinou, 2007). In switching crack model the crack is considered either fully open or fully closed. Further, switching crack models are associated with chaotic and quasiperiodic vibrations that are not seen in experimental testing. Recently, a number of papers have used more realistic trigonometric functions to describe the crack breathing mechanism of a rotating shaft (Cheng et al., 2011; Sinou, 2008).
