Running accuracy and stiffness of spindle units in a machine tool have a crucial influence on the accuracy and reliability of the whole machine. Fatigue life calculation of bearings in spindle units is important to ensure the good performance of spindle units and to design machine tools scientifically.
In order to predict the fatigue life of rolling bearings used in machine tools, the stresses generated at the contact surface of interface are needed. This stress distribution is mainly determined by the pressure acting on the contact surface. Accurate calculation of pressure distribution can be done by FEM, which considers not only the generator shape but also the length in the contact state. The calculation of pressure distribution requires great computational efforts, which is more important in the case of repeating the calculation of many contacts in complex rolling pairs than in the case of simple contacts.
In the previous studies, several methods were used for the fatigue life of bearings, but they failed to analyze the effect of the roll profile and ring misalignment on the bearing fatigue life in a direct way.
Having developed a mathematical model for the fatigue life calculation of cylindrical roller bearings widely used in machine tool spindles, Kim Myong Il, a researcher at the Faculty of Mechanical Science and Technology, proposed a reasonable roller profile by calculating the fatigue life of bearings of three roller profiles and comparing them by FEM.
The results showed that the stress distribution is significantly lower for circular or logarithmic correction than for rectilinear roller generators, but the stress distribution is higher for circular correction, and the overall logarithmic correction significantly improves the fatigue life by 4.5 times.