The effect of the uncertain initial angular misalignment on fatigue life of spindle-bearing system

The initial angular misalignment due to mounting error is unavoidable and uncertain during the application of rolling element bearings. The effects of the uncertainty of the initial angular misalignment on fatigue life of angular contact ball bearings and spindle system are investigated. To achieve this, the contact forces of ball bearings in spindle system are analyzed based on the system model considering initial angular misalignment and spindle speed. Two initial angular misalignment cases are taken into account, and the angular misalignment sample is extracted for each case by Monte carlo sampling method. The fatigue life results for each ball bearing are obtained. The results show that the uncertain initial angular misalignment can lead to the rating life dispersion of ball bearings and the degree of rating life dispersion is related to the angular misalignment case and spindle speed. Based on the reliability theory of series system, the spindle system rating life is obtained, the probability density distribution and cumulative distribution are both presented. The results show that two angular misalignment cases produce significantly different effects to the rating life and fatigue life distribution of spindle system.