As the operating conditions of rolling bearings become increasingly demanding, traditional steel bearings can no longer fully meet the performance requirements of critical equipment. Silicon nitride full ceramic ball bearings, with intrinsic properties such as a low thermal expansion coefficient, low density, corrosion resistance, and wear resistance, offer significant advantages in extreme temperatures, high-speed operation, and harsh corrosive environments. As a result, they have become a key technical solution for the core transmission systems of high-end equipment. However, the dynamic evolution of their service performance under varying operating conditions—such as load and speed—remains insufficiently understood. This study systematically investigates the service performance evolution mechanism of silicon nitride full ceramic ball bearings under self-lubrication conditions. The key findings will provide a theoretical foundation for optimizing and regulating performance under extreme operating conditions.

The fixed-setting face-milled curvilinear cylindrical gear features teeth that are arc-shaped along the longitudinal direction. Some researchers hypothesize that this arc-tooth may enhance the lubrication conditions of the ge... | Find, read and cite all the research you need on Tech Science Press

Curvilinear cylindrical gear drives are a type of parallel-axis gear set, and the longitudinal geometrical shape of the gear teeth is a part of the circular arc. This study aims to develop a curvilinear cylindrical gear drive with superior transmission performance. This study proposes a curvilinear cylindrical gear drive with a parabolic profile. The gear tooth surfaces are generated by a face-milling cutter with a straight-line profile, and the matching gear tooth surfaces are generated by a face-milling cutter with the parabolic profile. Initially, mathematical models of the gear set are described based on the theory of gearing. The finite element method and tooth contact analysis algorithms were applied to contact and bending stress analyses. Finally, four numerical examples are provided to illustrate the transmission performance of the curvilinear cylindrical gear drive with the parabolic profile. The study results show that curvilinear cylindrical gear drives have superior transmission performance compared to those with a straight-line profile.

Current research on curvilinear cylindrical gears primarily focuses on symmetric teeth, with little attention given to curvilinear cylindrical gears with asymmetric teeth. To investigate the impact of asymmetric tooth design on the meshing performance of curvilinear cylindrical gears. Two types of curvilinear cylindrical gear with asymmetric tooth are proposed. one is generated by a spread-blade cutter, and the other uses two different types of fixed-setting cutters to generate the concave and convex tooth surfaces of the gear respectively. The tooth profiles on both sides of the tooth of the proposed gear have unequal pressure angles, and the gear is asymmetric in the longitudinal direction. Two mathematical models of the gear tooth surfaces were derived based on the enveloping theory. A quasi-static finite element model of the gear pair was established for stress analysis, based on the mathematical model of the tooth surface. The influence of asymmetrical parameters, milling cutter radius, and other factors on the contact pattern, working pressure, bending stress, transmission error, and load distribution coefficient was investigated. The research shows that when the longitudinal asymmetry coefficient is 10 mm, the root bending stress increases by 21.5%, and the axial thrust force rises to 2.23 N. Reducing the pressure angle from 25° to 15° decreases root bending stress by 35%, transmission error fluctuation by 52%, and eliminates single-tooth contact. Smaller contact patterns reduce thrust force and improve gear performance. Larger contact patterns increase edge contact pressure and transmission error amplitude. The study suggests avoiding longitudinally asymmetric curvilinear gears and recommends gears with smaller pressure angles for smoother operation.