Centrifugal expansion of high-speed spindle and its influences on bearing dynamic characteristics

Focusing on a high-speed spindle system, the shaft and the bearing inner ring are modelled as a beam with the same cross-section and a hollow disk, respectively. The radial elastic deformations of the spindle shaft and the bearing inner ring under centrifugal forces are investigated. The changes of the connected state between the shaft and the bearing with speed are analyzed as well. Considering the centrifugal expansion of rotating components, a dynamic model for the high-speed spindle bearing is given with experimental verification. On this basis, the centrifugal influence on the radial preload state of spindle bearings are studied, and then the rules that how dynamic properties of the high-speed rolling bearing change with the speed are revealed. The results show that, the contact angles decrease, while the contact loads increase with the radial expansion deformation. Both the axial stiffness and the radial stiffness of spindle bearings decrease when the rotating speed increases. The radial expansion deformation of bearing inner rings due to the centrifugal force has an ignorable influence on the axial stiffness of bearings, while it can increase the radial stiffness of bearings?to a certain extent.