A 3D nonlinear finite element method for the dynamic analysis of rotating rotor with a transverse crack

A general and efficient method is presented in this paper for studying the effects of unbalance on the breathing mechanism of crack. Based on 3D finite element models combined with a nonlinear contact approach for crack modeling, the method is free from the assumption of weight-dominance and can be used to gain deep insights into the breathing mechanism of crack. In order to greatly reduce the computational time, a complex free-interface component mode synthesis (CMS) method is employed to reduce the order of the model. Based on the proposed method, the effects of unbalance on the breathing mechanism of crack are discussed. Numerical results show that the unbalance can lead to significant changes in the breathing of crack, even when the unbalance force is about an order of magnitude smaller than the self-weight. Moreover, the level and orientation of the unbalance have also remarkable effects on the breathing behaviors of crack. Besides, a new universal non-steady breathing phenomenon of crack is first found in this paper, which denotes that the breathing speed of a crack is fluctuated over one revolution when there exists residual unbalance in the cracked rotor.