Vibro-Acoustic Behavior of Unbalanced Shaft-Bearing-Pedestal Coupled System with Bearing Faults

This paper deals with the effect of faults and shaft unbalances on the rolling element bearings (REBs) vibro-acoustic behavior. In addition, the vibro-acoustic behavior of the bearing is investigated from the perspective of human visual and auditory senses. First, a dynamic model for an SKF 6205 bearing is considered. This dynamic model includes a shaft, inner ring, outer ring, and bearing pedestal that includes six degrees of freedom (DOF). The nonlinear contact between the bearing balls and the inner/outer rings of the REB is considered using the Hertzian contact theory. To find the displacement and velocity of the inner ring, outer ring, and bearing pedestal, one can solve six nonlinear partial differential equations with the Range-Kutta method. The results show a 4.65% error in the peak-to-peak time response value compared with the reference experimental results, which is a good agreement. The sound pressure level (SPL) in the far field can be calculated assuming the REB three components as cylindrical sound sources. It is very interesting to know the fault detection capability of the human being without using auxiliary tools. By comparing the results, it is shown that sound is a better measure for humans than observing the vibration of the bearing pedestal. Also, without the use of auxiliary tools, humans cannot detect incipient faults either through the sound or vibration of the REBs. It is very clear for humans to identify the shaft eccentricity with both ears and eyes. In addition, in this article, the nonlinear behavior of the dynamic model with increasing fault severity has also been investigated.