Development of rolling element bearing misalignment test rig

Abstract

Rolling element bearing stiffness has a significant influence on the dynamic behavior of rotating machinery, and stiffness variations caused by bearing misalignment may affect the response of the overall rotor–bearing system. This thesis addresses the development of a test rig for investigating stiffness changes in a single-row deep groove ball bearing under intentional outer-race misalignment. Two test-rig concepts are considered, both targeting the same objective through different methodologies. Concept A is based on direct load–displacement measurements, whereas Concept B uses shifts in natural frequency as an indirect indicator of stiffness variation. The work is based on an existing laboratory rig at the machine dynamics lab at LUT University and is supported by CAD design in SolidWorks, MATLAB-based rotor-dynamics modeling using the RoBeDyn toolbox, and finite-element simulations in ANSYS. Four design cases are evaluated numerically in terms of deformation, equivalent stress, reaction force distribution, shaft slope, and displacement sensitivity to bearing stiffness degradation. The results show a clear progression from the initial load-limited concept toward a final combined loading configuration with improved structural behavior, alignment control, and measurement sensitivity. The frequency-shift-based concept is also assessed as an alternative dynamic approach and is found to depend strongly on rotor geometry and on the magnitude of stiffness reduction. The thesis provides a justified basis for the final test-rig design and for further experimental study of changes in bearing stiffness caused by outer-race misalignment.