Focusing on pedestal looseness fault often occurring in practical engineering, a new looseness model is presented by considering respective advantages and disadvantages of all kinds of pedestal looseness model. By using finite element method, the looseness fault is simulated and the fault features are obtained. The simulation results show that when the amplitude of equivalent looseness mass is less than the looseness clearance, the system motion is from period-one through period-two to period-four, amplitudes of low frequency components gradually increase and the axis orbit changes from ellipse to twist with the decrease of looseness stiffness. When the amplitude of equivalent looseness mass is greater than the looseness clearance, high multiple frequency components and continuous spectra appear and axis orbit is similar to a trapezoid due to axis motion restrained by bilateral constraint. These fault features that obtained in different conditions are helpful to diagnose pedestal looseness fault in rotor system.

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