LAUSR

Vibration signal modeling of a localized defective rolling bearing under unbalanced force excitations is carried out in this paper. A mass-spring-damping system with eight degrees of freedom is derived to consider the transverse vibrations and high frequency resonances of the rotor and bearing pedestals. External excitations come from the unbalanced mass and self-weight of the rotor. Due to the Hertz contact and bearing clearance, the dynamic model is coupled by the nonlinear stiffness. The inner/outer race defects are localized and modeled by additional contact deformations. The Runge-Kutta method is utilized to solve the nonlinear coupled differential equations and vibration signals with and without defects are obtained. Through envelope analysis, the fault characteristic frequencies of inner/outer raceway defects with and without unbalanced force excitations are presented. Detailed comparisons show that the unbalanced force excitations have significant influence on the fault characteristic frequencies. Finally, dynamic tests on a typical rotor-bearing system are conducted to verify the theoretical results.