Effect of an unbalanced rotor on dynamic characteristics of double-row self-aligning ball bearing

Abstract

This paper aims at predicting the non-linear dynamic behavior of a self-aligning ball bearing supported on an unbalanced shaft system under varying shaft speed and radial load conditions. A mathematical model is developed for analyzing the behavior of the shaft-bearing system under dynamic conditions. The nonlinear stiffness, damping, and clearance act as the source of nonlinearity. The balls and the race contacts are considered as non-linear springs and the contact deformation is defined using Hertzian contact theory. A fully populated stiffness matrix characterizing the bearing stiffness in all 3 directions (x,y,z) has been used. The phase diagrams and Poincaré maps are used to characterize the vibrations response and it has been observed that the system undergoes gradual or sometimes sudden changes in the dynamic behavior with the variation in parameters. The route to chaos analysis with considering multi-periodic to chaotic response has been done with parametric variations. It was observed that the periodicity of the system tends to increase with the increase in shaft's rotational speed while it decreases with the increase in radial load. In order to validate the simulated results, a test-rig has been set up, where the vibration data of the rotor-bearing system is acquired and further analyzed. The results obtained from experimental data were found to be in good agreement with the numerical simulations. Hence, these observed results will provide the basic platform in designing of such double-row self-aligning shaft-bearing systems.