The shaft misalignment under mixed lubrication is an important factor affecting the running performance of the bearing, which can occur under heavy load and unsatisfactory assembly. This paper presents a misaligned journal mixed lubrication model coupling for the asperity contact effect, elastic deformation, viscosity–temperature, and viscosity–pressure effect. The finite difference method was employed to calculate the model, and an experimental apparatus designed in this paper was used to test the friction and temperature characteristics of the specimens. The results show that the pressure field, film thickness, and elastic deformation of the bearing conformed to asymmetric distribution along the axial direction under misalignment conditions and there was a notable end side effect. In addition, the frictional force and side leakage flow were evidently enhanced with the increase in the inclination angle in a certain range. The experimental results showed that there was a visible wear phenomenon on the end sides of the bush and shaft. The research results are beneficial for understanding the mixed lubrication mechanism of misaligned journal bearing.

This study conducted longitudinal ultrasonic-assisted milling (UAM) tests and optimized a combination of milling technological parameters to achieve high-quality machining of TC18 titanium alloy. The motion paths of the cutter under the coupled superposition states of longitudinal ultrasonic vibration and end milling were analyzed. Based on the orthogonal test, the cutting forces, cutting temperatures, residual stresses, and surface topographical patterns of TC18 specimens under different UAM conditions (cutting speeds, feeds per tooth, cutting depths, and ultrasonic vibration amplitudes) were examined. The differences between ordinary milling and UAM in terms of machining performance were compared. Using UAM, numerous characteristics (including variable cutting thickness in the cutting area, variable cutting front angles of the tool, and the lifting of the cuttings by the tool) were optimized, reducing the average cutting force in all directions, lowering the cutting temperature, increasing the surface residual compressive stress, and significantly improving the surface morphology. Finally, fish scale bionic microtextures with clear, uniform, and regular patterns were formed on the machined surface. High-frequency vibration can improve material removal convenience, thus reducing surface roughness. The introduction of longitudinal ultrasonic vibration to the end milling process can overcome the limitations of traditional processing. The optimal combination of UAM parameters for titanium alloy machining was determined through the end milling orthogonal test with compound ultrasonic vibration, which significantly improved the surface quality of TC18 workpieces. This study provides insightful reference data for subsequent machining process optimization.

To achieve high-quality machining of the 2195 aluminum-lithium alloy, this paper presents an experimental study on the effect of milling processing parameters on milling forces and surface topography, during which conventional milling and longitudinal-torsional ultrasonic vibration milling of the 2195 Al-Li alloy were performed. The characterization of the tool tip trajectory illustrates some of the advantages of ultrasonic machining, which include variable depth of cut and tool chip pulling. The differences in milling forces between conventional milling and longitudinal-torsional ultrasonic vibration machining were compared using orthogonal tests, and the effect of ultrasonic vibration on milling forces was investigated in detail. The maximum reduction of milling force Fy in the feed direction under the influence of torsional vibration is 62% and 54% for larger feed per tooth and cutting depth, respectively. The high-frequency impact generated by the longitudinal vibration not only reduces the chip accumulation on the surface, but also smooths out the tool-tooth scratches and creates a regular surface profile. In addition, the characteristics of the milling force signals of the two machining methods were analyzed, and the analysis of the spectrum of the collected milling forces revealed that the ultrasonic vibration caused the high-frequency components of the milling forces Fy and Fz. The orthogonal result analysis and single-factor result analysis verified the superiority of ultrasonic machining, provided parameter selection for subsequent aluminum-lithium alloy machining, and bridged the gap of longitudinal torsional ultrasonic vibration machining of 2195 aluminum-lithium alloy in the study of milling force.

The proposed lubrication theory of textured journal bearing is a major innovation in the study of the tribological properties of surface morphology. When it comes to the study of surface topography, it is essential to consider the effect of surface roughness when analyzing the characteristics of journal bearing. In this paper, a Reynolds equation containing longitudinal roughness is established for journal bearing and solved by the finite difference principle to obtain the bearing load and friction characteristics. Subsequently, a combination of laser etching and ultrasonic vibration milling processes was used to prepare 5 µm, 20 µm, and 40 µm bearing friction subsets with square micro-texture surfaces. The analysis of the results shows that the surface roughness distributed in the non-texture region can substantially increase the oil film pressure. When the roughness profile and the surface weave work together, the presence of a surface texture with an optimum depth of 5 µm within a roughness range of less than 1.6 µm can improve the load-bearing characteristics by a maximum of 43%. In the study of the preparation of textured bearing friction substrate, it was found that laser etching can ablate the surface of the friction substrate to a depth greater than 20 µm with the ideal effect, while the surface texturing to a depth of 5 µm is more suitable using an ultrasonic vibration processing process. In the simplified journal bearing operating condition, the frictional wear test shows that if the effect of roughness is considered, the frictional force of the depth of 20 µm and 40 µm is significantly reduced and changes less with increasing load, while the frictional force of the textured frictional pair with a depth of 5 µm is improved but significantly affected by the load carrying capacity. Therefore, when the difference between the roughness profile and the depth of the texture is of a small order of magnitude, it indicates that the effect caused by the roughness factor is not negligible.

The conical bearing can withstand both journal and axial load because of the conical-shape fluid film, and an investigation concerning the thermodynamic lubrication and stability properties is proposed for a conical hydrostatic/hydrodynamic floating ring bearing theoretically and experimentally. The finite element method is coupled with the finite difference method to solve the variable-viscosity Reynolds equations, thermal energy equations, and the corresponding boundary conditions for the inner and outer films in a floating ring equilibrium state, and the conical bearing-rotor dynamic and stability performance models are built up with the perturbation theory and Routh–Hurwitz method. The primary characteristics parameters that are obtained under different operational conditions suggested that there presents a significant temperature gradient distribution over the lubricated domain, the thermal effects decrease the load carrying capacity, friction power loss, and stiffness and damping coefficients, and the viscous dissipation influences the variation of threshold instability speed with eccentricity and reduces its maximum value. In experiments, the temperature distributions of the oil leakage flow are measured to compare with the calculated results for the validation of the mathematic model using an infrared thermal imager, and the thermal effects need to be taken into consideration for the bearing lubrication analysis and design.