Thermal Stress Analysis of a Ball Bearing by Finite Element Method

High cutting speeds and feeds are essential requirements of a machine tool structure to accomplish its basic function which is to produce a work piece of the required geometric form with an acceptable surface finish at as high a rate of production as is economically possible. Since bearings in high speed spindle units are the main source of heat generation. Friction in bearings causes an increase of the temperature inside the bearing. If the heat produced cannot be adequately removed from the bearing, the temperature might exceed a certain limit, and as a result the bearing would fail. To analyse the heat flow in a bearing system, a typical ball bearing and its environment has been modelled and analysed using the finite element method. The maximum temperature in the bearing has been calculated as a function of heat generation with the rotational speed as a parameter. The goal of this analysis is to see how fast the temperature changes in the bearing system with respect to rotational speeds. In this thesis, at high speed range, a steady state thermalstress simulation is performed by using FEA method to investigate temperature distribution of the bearing and the result shows that the temperature increases gradually with increase in rotational speed and it is validated by analytical formulation done. Further the increase of rotation speed the inner ring centrifugal displacement increases which causes larger contact deformation and stress. The dynamic stiffness of the variable preload bearing is analysed analytically and it is found that the radial stiffness decreases with increase in rotational speeds.