Advantages of pulse force model over geometrical boundary model in a rigid rotor-ball bearing system

For a local defect modeling in a defective bearing-rotor system, there mainly exist two types of commonly-used models. One is a description of the geometrical boundary simulating a real local defect (GB model), while the other one is a depiction of the consequence -the pulse force produced by a rolling element striking the local defect (PF model). Dynamic equations of defective ball bearing-rotor system based on the two local defect models are established. The defective systems depending on the two defect models reflect the similar dynamic characteristics such as the defect frequencies, the primary resonance and the super-harmonic resonance. However, compared to the GB model, the PF model based governing equation is more suitable to be processed by the classical method for nonlinearities which exists in a defective bearing-rotor system. A frequency-domain method -harmonic balance (HB) method which can obtain the semi-analytical solution is utilized to solve the PF model based governing equation and prove the calculation efficiency. Besides, a rigid rotor-ball bearing experiment system is established, the phenomena such as the defect frequencies, resonance and super-harmonic resonances in theoretical analysis reflected together by two defect models are verified qualitatively. Therefore, it can be concluded that the PF model has an advantage over the GB model for the dynamic analysis. Moreover, the discoveries in this paper may supply some clues for diagnosis of a defective rolling bearing system.