Search Results (54)

Many low-temperature applications, such as rocket engines and liquefied natural gas (LNG) transport pumps, necessitate ultra-low-temperature operational environments. In these conditions, the properties of lubricating oils and greases are significantly influenced by temperature, leading to the widespread adoption of solid lubrication. Currently, there is no international research regarding the influence of bearing coatings on the subsurface stress distribution in raceways. The Lundberg–Palmgren (L-P) theory states that subsurface stress variations govern bearing lifespan. Therefore, this paper utilizes existing formulas and Python programming to calculate the subsurface stress field of the inner raceway in a MoS₂ solid-lubricated angular contact ball bearing. Furthermore, it analyzes the impacts of factors such as coating material properties, slide-to-roll ratio, traction coefficient, and load on its subsurface stress field. The results reveal that for solid-lubricated ball bearings, as the load increases, the maximum subsurface stress shifts closer to the center of the contact area, and the maximum subsurface shear stress becomes more concentrated. As the traction coefficient increases, the stress on the XZ-plane side increases and its position moves closer to the surface, while the opposite trend is observed on the other side. Additionally, the maximum value of the subsurface von Mises stress is approximately 0.64P₀, and the maximum value of the orthogonal shear stress component τ_yz in the subsurface is approximately 0.25P₀. Full article

In order to improve the lubrication efficiency in the bearing cavity, this study establishes a simulation model of the fluid domain of the bearing cavity based on the computational fluid dynamics (CFD) method and systematically studies the flow characteristics of the lubricant and its lubrication mechanism in the high-speed rotary bearing. In the process of high-speed bearing operation, the lubricant is subject to the combined effect of centrifugal force and contact pressure, gradually spreads to both sides of the steel ball, and forms a stable oil film after injection from the nozzle. However, due to the influence of high pressure distribution in the contact area, the actual formation of the oil film coverage is relatively limited. In order to further optimize the lubrication effect, this study focuses on investigating the influence law of different injection speeds and rotational speeds on the bearing air curtain effect. The results of the study show that when the air curtain effect is enhanced, there will be significant shear interference on the trajectory of the lubricant, which is manifested in the phenomenon of “buckling” at the end of the lubricant, thus reducing the lubrication efficiency. To address this problem, this study innovatively proposes the air curtain obstruction coefficient K as a quantitative evaluation index, and through numerical simulation, it is found that the lubricant can effectively overcome the air curtain obstruction and achieve a better lubrication coverage when the value of K is reduced to below 0.4. Based on this finding, the study further confirmed that the lubrication efficiency of bearings can be significantly improved under different operating conditions by rationally regulating the injection rate. Full article

This paper addresses the vibration characteristics of angular contact ball bearings in aircraft engines under variable load conditions. Based on multibody dynamics theory, a dynamic model of the bearing was established. Vibration data under actual operating conditions were obtained using an experimental test platform. This study systematically investigated the influence of rotational speed, axial load, and radial load on the vibration acceleration level of the bearing outer ring. Through a comparison of simulation and experimental data (with an error rate below 10%), the reliability of the model was validated. The results indicate that the bearing vibration acceleration level exhibits a nonlinear increasing relationship with rotational speed. An increase in radial load significantly amplifies the amplitude of acceleration-level fluctuations, while appropriately increasing axial load can reduce bearing vibration intensity. Under variable load coupling conditions, the dynamic interaction between axial and radial forces results in complex nonlinear vibration responses, with a 2 s acceleration time achieving the optimal balance between vibration suppression and efficiency (steady-state average of 70.4 dB). Additionally, the morphological characteristics of the cage center-of-gravity trajectory (such as trajectory disorder and poor smoothness) are closely related to vibration characteristics, revealing the critical role of dynamic load changes in bearing stability. The research results provide a theoretical basis for optimizing the operating conditions, vibration control, and reliability design of aircraft engine bearings. Full article

This article describes a machine vision-based method for measuring the angular velocity of a rotating disk to characterize the viscous resistance of a ball bearing. A bright marker was attached to a disk connected to a shaft supported by two ball bearings. Rotation of the marker was recorded with a digital camera. A simple algorithm was developed to track the trajectory of the marker and calculate angular displacement of the disk. For accurate detection of the rotating marker, the algorithm employed Multi-Otsu thresholding and the Least Squares Method (LSM). Verification of the proposed method was carried out through a direct comparison between the predicted rotational speeds and measured ones by a commercial tachometer. It was demonstrated that the percentage error of the proposed method was less than 1.75 percent. The evolution of angular velocity after motor power-off was measured and found to follow an exponential decay law. The exponent was found to remain consistent regardless of the induced rotational speed. This proposed measurement method will offer a simple and accurate non-contact solution for monitoring angular velocity and characterizing the resistance of a bearing. Full article

To investigate the temperature rise characteristics and tribological performance of angular contact ball bearings equipped with polymer-based self-lubricating retainers under oil-depleted conditions. PTFE-based composite retainers were fabricated using cold-press sintering technology. Comparative experiments on 7206C were conducted on three bearing configurations (domestic, imported NSK, and YSU-S1/S2 self-lubricating retainer bearing) using a dedicated fatigue tester under oil-depleted lubrication. This study demonstrates that angular contact ball bearings equipped with PTFE-based self-lubricating retainers exhibit superior thermal behavior under oil-depleted conditions. Compared to domestic and imported NSK bearings, the retainer-equipped bearing reduced equilibrium temperatures by 2~3 °C versus NSK/domestic bearings, with 60% lower peak temperatures. The high speed further facilitates the formation of transfer films, resulting in a smoother raceway and notably enhancing the bearing’s temperature rise characteristics. This study establishes a material–process–performance framework, bridging polymer composites and industrial bearing design. Full article

To enable experimental research on the dynamic support stiffness of electric spindle bearings, the authors designed a magnetic non-contact excitation and test device that can test the support stiffness of electric spindle bearings under a rotating state. The device includes load excitation and displacement detection components, which can collect the load loading and displacement data of electric spindle bearings under machine state in real time. The radial and axial loads can be applied at the same time, and the displacement detection component adopts a high-precision displacement sensor, which can measure the displacement data generated by the electric spindle bearing under the action of the excitation component in real time. A magnetic loading method was proposed for testing the supporting stiffness of the front and rear bearings in electric spindles along the three orthogonal directions of radial X/Y and axial Z. According to the designed device and test method, the dynamic support stiffness of an electric spindle bearing in a vertical machining center is tested, and the variation trend of the bearing support stiffness under the combined action of axial load, radial load and rotational speed is analyzed. Full article

The dynamic interactions among the internal components of aero-engine main shaft bearings under unsteady-state conditions are intricate, involving clearance collisions, contact, friction, and lubrication. The dynamic characteristics of bearings significantly influence the performance and stability of mechanical systems. This study establishes a rigid–flexible coupling dynamic model for angular contact ball bearings with two-piece inner rings based on Hertz contact theory and lubrication theory. It systematically analyzes the dynamic characteristics of bearings under the coupling effects of acceleration, deceleration, and impact load. This study explores the influence of various loads, bearing speeds, and groove curvature radius coefficients on the dynamic characteristics of bearings. The findings indicate that the uniform speed phase of a bearing is highly responsive to impact load, followed by the deceleration phase, while the acceleration phase shows lower sensitivity to impact load. The groove curvature radius coefficient significantly affects the contact stress between the ball and its corresponding raceway, with contact stress increasing as the groove curvature radius coefficient rises. As the axial load decreases and the radial load, bearing speed, and groove curvature radius coefficient increase, there is a rise in pocket force, guiding force, and maximum equivalent stress of the flexible cage. Impact load leads to short-term intense fluctuations in the thickness of the bearing oil film, which can be alleviated by an increase in axial load. The oil film thickness firstly increases and then decreases with respect to the groove curvature radius coefficient. Furthermore, variations in bearing speed notably influence the thickness of the bearing oil film. This study analyzes the dynamic characteristics of bearings under the coupling effects of acceleration, deceleration, and impact load, offering insights for the design and optimization of angular contact ball bearings with two-piece inner rings. Full article

Solid-lubricated rolling bearings are widely used in the aerospace field and are key components to support spacecraft rotors. During the start-up of the engine, the sharp acceleration may cause bearing skidding, resulting in damage of the solid lubricating film and a reduction in the remaining useful life of the bearing. However, the existing research on the tribo-dynamic responses of solid-lubricated ball bearings mostly relies on semi-empirical tribological models, which are limited in their ability to reveal the micro–macro sliding mechanisms of the ball–raceway contact interface. In this paper, a novel tribo-dynamic model for solid-lubricated angular contact ball bearings is developed by applying Kalker’s rolling contact theory to the Gupta dynamic model. The interpolation method is adopted to calculate contact parameters to improve the model’s efficiency. Using the proposed model, the dynamic response of the bearing in the acceleration process is studied, and the mechanism and influence characteristics of skidding, over-skidding, and creepage of the rolling element are analyzed. The results show that the main reason for skidding is that the traction force is not enough to overcome the resistance, and the gyroscopic effect is the main cause of over-skidding, which follows the principle of conservation of the angular momentum of the ball. Full article

This work develops a comprehensive analysis method to examine the nonlinear dynamic response of angular contact ball bearings (ACBBs) with variable clearance. Based on the elastic contact theory and friction principle, the nonlinear contact-impact behavior of the ACBB is systematically investigated. A multibody dynamics model incorporating three-dimensional clearance effects is developed. First, the nonlinear vibro-impact dynamics model of the ACBB is presented considering the influence of variable clearance. Second, the kinematic analysis of the ACBB with clearance is planned, and performance tests are performed under variable conditions, which demonstrate the effectiveness of the proposed method. Furthermore, a comparative analysis of a numerical simulation of the ACBBs with variable clearance is performed. The results show that the increase in rotation speed and external load would cause the high-frequency contact impact between ball and raceway. The decline of the deviation ratio for the cage’s mass center velocity illustrates that the motion trajectory of ACBB would be irregular. Full article

In aerospace technology, angular contact ball bearings are required to exhibit extremely high operational precision, necessitating real-time monitoring of their wear status to conduct pre-failure analysis. Although extensive studies have been conducted on the wear characteristics of angular contact bearings, further in-depth research is still required to enhance the accuracy of bearing life predictions. To address the imprecision in wear life prediction for angular contact ball bearings, this article proposes a refined wear calculation model based on dynamic load distribution. The model calculates the dynamic load distribution between the inner and outer rings and the raceway under mixed lubrication conditions. Integrating the dynamic load distribution methodology with the wear calculation model, the dynamic contact characteristics of angular contact bearings can be more accurately characterized. Building on this foundation, a dynamic analysis model considering dynamic wear in the bearing contact zone is established. The vibration characteristics of bearings under varying loads are analyzed, and vibration experiments under different load conditions are conducted. Through vibration spectrum analysis, the influence patterns of wear characteristic frequency bands in the wear model on the pre-failure state of bearings are further elucidated. This study provides a theoretical basis for bearing wear life prediction analysis. Full article

Under mixed lubrication, the macro size is affected by the wear of the surface roughness peaks, which results in degradation of the bearing accuracy. To study the wear characteristics of rolling bearings under mixed lubrication, based on the elastohydrodynamic lubrication theory and Archard wear model, and considering the coupling of the oil film and roughness, a wear prediction model of angular contact ball bearings under mixed lubrication was established, and the influence of the working parameters and hardness on bearing wear was analyzed. The results show that the wear depth of the outer grove increases with an increase in the load, or a decrease in the rotational speed or the initial viscosity of lubricating oil. The load has the most significant effect on the wear depth of the outer grove. There is a critical value for the load, rotational speed, and initial viscosity of the lubricating oil, which varies with the parameters of other working conditions and the hardness of the materials. When the increase in load exceeds the critical value or the rotational speed and initial viscosity of lubricating oil are less than the critical value, the outer groove fails because the wear depth exceeds the critical value of wear depth. The ratio of the load on the rolling element to the hardness of the outer grove at different entrainment speeds and initial viscosities of lubricating oil can be used to predict the wear degree of the outer grove. When the ratio is greater than a certain threshold, the outer grove is faulted owing to wear, and the threshold decreases with an increase in the initial viscosity of lubricating oil or the decrease in rotational speed. Full article

A textured surface topography can be used to improve the lubrication performance of bearings. These improvements are closely related to the design of the textured topography. Therefore, studying the effect of the textured topography of rolling bearings on lubrication performance is significant. This study used computational fluid dynamics (CFD) technology to simulate and analyze the lubrication of an angular contact ball bearing under different working conditions. We studied the influence of a textured topography with different area occupancy rates on the oil-phase volume fraction, as well as the lubrication effect of the textured surface on the bearing’s inner ring and chamber at different rotational speeds and oil inlet speeds. We conducted friction characteristic experiments on point–contact friction pairs using a friction and wear tester. The effects of different loads and rotational speeds on the friction characteristics and surface wear of textured and smooth surfaces were analyzed. The results indicate that the oil-phase volume fraction is always higher than that of the conventional bearing in the inner ring and chamber of a textured bearing. The textured bearing exhibited better lubrication and friction performance. Different textured topographies have different positive effects on lubrication performance, and the influence of the working conditions should be fully considered to achieve these improvements. Full article

During the heat treatment process, bearing rings are subjected to drastic temperature variability and complex microstructural evolution, which result in deformation, high residual stresses, operational instability and a limited operating life. However, the underlying relationship between temperature, phase transformation, and deformation has not been fully revealed in previous research. As a result, it is difficult to accurately control the roundness of bearing rings during the heat treatment process. Therefore, a combination of numerical simulations and experimental methods was employed to analyze the heat treatment process of the rings of angular-contact ball bearings (ACBB) (7008C). Firstly, according to the multiple coupling theory of thermal, phase-transition, and stress–strain fields, a model for the numerical simulation of the quenching and tempering process was established. Secondly, the thermal–physical properties of the material were calculated using the Jmatpro 7.0 software, and the quenching and tempering processes were numerically simulated using the Deform software. Subsequently, the evolution of the stress, phase-transformation, and deformation behaviors of bearing rings during the quenching and tempering were studied in detail. Finally, the roundness errors of the bearing rings were obtained by a coordinate-measuring machine (CMM). The results showed that the axial and radial stress distributions at the surface and center of the bearing rings were significantly different. The bearing rings experienced uneven expansion and deformation. The roundness errors of the inner diameter and outer diameter of the inner ring were 0.0386 mm and 0.0423 mm, respectively. The roundness errors of the inner diameter and outer diameter of the outer ring were 0.0202 mm and 0.0180 mm, respectively. In this study, the mechanism of the effect of the temperature variation and phase transformation on deformation during the quenching and tempering process was revealed in detail. This provides a reference for controlling the roundness of bearing rings in actual production processes. Full article

The problem of estimation the friction torque in operating miniature ball bearings lubricated with oil or grease is a complex one. Generally, in an angular contact ball bearing (ACBB), various types of losses can appear including losses caused by kinematics in ball-race contacts (rolling, sliding and pivoting), losses between the cage and the balls and between the cage and the guiding race and losses generated by lubricant, especially at high speeds. In the miniature ACBB, the applied loads have generally low values, and some losses can be ignored. In these circumstances, the most important contribution to the increase in the losses in miniature ACBB is the presence of the lubricant. In normal rolling bearings, the lubricant has an important contribution to decrease the losses and increase the reliability in miniature ball bearing; the lubricant (oil or grease) leads to the increase in the losses compared to the dry or limit lubrication conditions. The catalogues of various rolling bearing companies have not provided more details referring to the friction losses in miniature ball bearings. In order to evaluate the total friction torque in the rolling bearings, some empirical complex relations are presented via the SKF methodology, which can be applied only to moderate and high loads applied to the rolling bearings. Other empirical relations are presented by the Schaeffler catalogue. Based on previous experiments, the authors determined the friction torque in a 7000C ACBB with the spin-down method. The experimental results were correlated with the results obtained via the theoretical model developed by Houpert for IVR lubrication conditions. The theoretical results evidenced that the hydrodynamic rolling resistance generated by the lubricant is the most important component of the friction torque for 7000C ACBB. The experimental and theoretical results were compared to the results obtained according to the SKF and Schaeffler relations. The experimental results and the results obtained with the Houpert model generally had higher values compared to the results obtained with the SKF and Schaeffler relations. Full article

This article presents a general numerical method to establish a mathematical model of a bearing–rotor–disk system. This mathematical model consists of two double-row angular contact ball bearings (DRACBBs), a rotor and a rigid disk. The mathematical model of the DRACBB is built on the basis of elastic Hertz contact by adopting the Newton Raphson iteration method, and three different structure forms are taken into account. The rotor is modeled by employing a finite element method in conjunction with Timoshenko beam theory, and the rigid disk is modeled by applying the lumped parameter method. The mathematical model of the bearing–rotor–disk system is constructed by the coupling of the bearing, rotor and disk, and the dynamic response of the bearing–rotor–disk system can be solved by employing the Newmark-β method. The validation of the above mathematical model is demonstrated by comparing the proposed results with the results from the existing literature and finite element software. The dynamic characteristics of the DRACBBs and the dynamic response of the bearing–rotor–disk system are investigated by parametric study. A dynamic characteristic analysis of the DRACBB is conducted to ensure the optimal structure form of the DRACBB under complex external loads, and it can provide a reference for the selection of the structural forms of DRACBBs. Full article