Rolling bearing fatigue life is an essential criterion in industrial equipment design and manufacturing and requires precise maintenance and replacement predictions. ISO/TS 281:2007 and 16281:2008 are commonly used for angular contact ball bearing (ACBB) fatigue life calculations, but they do not account for the characteristics of individual bearing elements under combined loading conditions. This study proposes an enhanced formula for calculating fatigue life modification factors that considers individual element-specific contact loads and resulting film thickness variations. The proposed fatigue life formula provides longer life predictions than the conventional method of determining modification factors based solely on maximum contact loads. This difference is particularly noticeable in low-speed and/or heavy-loading applications. Analysis conducted using the proposed fatigue life formula on various factors affecting fatigue life revealed that fluid kinetic viscosity coefficients, temperature-associated density changes, and changes in radial loads and rotational speeds could significantly impact the fatigue life of ACBBs. The proposed fatigue life formula is expected to increase the accuracy of ACBB fatigue life predictions.

A self-compensated water-hydrostatic bearing is well known to have advantages in stiffness. In this paper, its concept is extended to a hydrostatic journal bearing for achieving higher stiffness. The finite element method is applied to analyze the load characteristics of the self-compensated hydrostatic journal bearing. The analysis results reveal that the self-compensated journal bearing has higher load capacity and higher stiffness than conventional, fixed capillary journal bearings, and that this benefit degrades in the case of high eccentricity. Thus, a spindle system with self-compensated journal bearings must be designed to ensure a sufficiently large load capacity. A rectangular type capillary is also introduced with consideration of the practical application of the self-compensated hydrostatic journal bearing. Theoretical analysis results show that the rectangular type capillary is more beneficial than conventional annular type capillaries in practical use. The experimental verification on the analysis method is made to show that the experimental results are in good agreement with theoretical results.