Showing papers on "Fluid bearing published in 2022"

Rolling Bearing Condition Monitoring Technique Based on Cage Rotation Analysis and Acoustic Emission

Abstract: The objective of this paper is to present an approach for the detection of change in rolling element bearings (REB) operating conditions that can lead to premature failure. The developed technique is based on the measurement of the kinematics of the bearing cage. The rotational motion of the cage is driven by the traction forces produced in the contacts of the rolling elements with the races. It is known that the cage angular frequency relative to shaft angular frequency is dependent of the bearing load, the bearing speed and the lubrication condition, as these factors are determinant for the lubricant film thickness and the associated traction forces. As an important part of REB failures are caused by misalignment or lubrication problems, any evidence of these conditions should be interpreted as an incipient fault. In this paper a novel method for the determination of the instantaneous angular speed (IAS) of the cage is developed. The method is evaluated in a deep grove ball bearing test rig equipped with the cage IAS sensor, as well as custom acoustic emission (AE) transducer and a piezoelectric accelerometer. The cage IAS is analyzed under different bearing loads and shaft speed, showing the dependence of the cage angular speed with the calculated lubricant film thickness. Typical bearing faulty operating conditions (mixed lubrication regime, lubricant depletion and misalignment) are recreated and it is shown that the cage IAS is dependent on the lubrication regime and is sensitive to misalignment. The AE signal is used as a lubrication regime evaluator as well. Experimental results show that the proposed technique can be used as a condition monitoring tool to detect abnormal REB conditions that can lead to premature failure.

Numerical simulation of ball bearing flow field using the moving particle semi-implicit method

Abstract: ABSTRACT The distribution of lubricating oil in the bearing cavity is of great significance to bearing lubrication and cooling. A new idea is provided to further study the ball bearings lubrication, to achieve effective lubrication of bearings. The flow field of oil injection lubrication ball bearings is studied by the moving particle semi-implicit (MPS) method. The accuracy of the numerical calculation method is verified by experiments. The oil distribution of the bearing lubrication flow field and churning torque of the ball and cage at different speeds are analyzed. The research results show the maximum oil content in the bearing cavity is distributed in the range of about 90° to 120°. As the increase of rotating speed, the number of particles in the bearing cavity decreases. The churning torque decreases with the increase of rotating speed and increases with the increase of the oil viscosity. This study provides a new numerical calculation method for the lubrication flow field of ball bearings.

Investigations for vibration and friction torque behaviors of thrust ball bearing with self-driven textured guiding surface

Abstract: Abstract In order to improve the starved lubrication condition of rolling bearings, three kinds of textures, namely dimple, groove texture, and gradient groove texture, were developed on the guiding surface of thrust ball bearings in this study. The results show that gradient groove texture has the one-way self-driving function of liquid droplets. The root mean square (RMS) value of vibration acceleration of gradient groove textured bearing (GGB) decreased by 49.1% and the kurtosis decreased by 24.6% compared with non-textured bearing (NB) due to the directional spreading effect of gradient groove textures on oil. The frequency domain analysis showed that the textures mainly suppressed the medium and high-frequency energy of bearing vibration, and the GGB was reduced the most with 65.3% and 48%, respectively. In addition, whether the grease is sufficiently sheared has a large impact on the oil guiding effect, and the friction torque of GGB could decrease by 10.5% compared with NB in the sufficiently sheared condition. Therefore, the gradient groove texture with oil self-driven effect on the guiding surface of rolling bearing can effectively improve the lubrication condition of the bearing and thus reduce the bearing vibration and friction torque, which has a promising application prospect.

Mixed-lubrication analysis of misaligned journal bearing considering turbulence and cavitation

Abstract: By integrating the average flow equation and Ng–Pan turbulence model using the boundary condition of mass conserving [Jakobsson-Floberg-Olsson (JFO)], a mixed lubrication model for misaligned bearing was established considering the effects of turbulence and cavitation. The numerical solution was obtained using a finite difference scheme. The results indicate that the frictional force and moment calculated using the JFO boundary condition are greater than those calculated using the Reynolds boundary condition under the constant external load. In high speed conditions, the turbulence begins to play a role, which makes the maximum oil film pressure and moment decrease and the minimum oil film thickness, cavitation zone, and friction coefficient increase. The boundary condition and turbulence have important effects on the equilibrium position of the axis. The misalignment leads to an obvious increase in the friction of the mixed lubrication area and a slight decrease in that of the hydrodynamic lubrication area.

Wind turbine main-bearing lubrication – Part 1: An introductory review of elastohydrodynamic lubrication theory

Abstract: Abstract. This paper is the first in a two-part study on lubrication in wind turbine main bearings. Elastohydrodynamic lubrication is a complex field, the formulas and results from which should not be applied blindly, but with proper awareness and consideration of their context, validity and limitations in any given case. The current paper, “Part 1”, therefore presents an introductory review of elastohydrodynamic lubrication theory in order to provide this necessary background and context in an accessible form, promoting cross-disciplinary understanding. Fundamental concepts, derivations and formulas are presented, followed by the more advanced topics of starvation, non-steady effects, surface roughness interactions and grease lubrication. “Part 2” applies the presented material in order to analyse wind turbine main-bearing lubrication in the context of available film thickness formulas and related results from lubrication theory. Aside from the main-bearing, the material presented here is also applicable to other lubricated non-conformal contacts in wind turbines, including pitch and yaw bearings and gear teeth.

Active fluid-film bearing with deep Qnetwork agent based control system

Abstract: Despite the fact that the hydrodynamic lubrication is a self-controlled process, we designed the control systems based on PI controller, adaptive PI controller, and DQN-agent to minimize the friction torque in a conical fluid-film bearing. The bearing construction allows the shaft axial displacement and, as the result, the regulation of the bearing average clearance due to the controlled supply pressure. The main challenge is that the friction torque minimization may lead to the loss of load-carrying capacity and the contact in the shaft-bearing tribocouple. The other challenge is that random events may have an influence on the hydrodynamic lubrication parameters therefore changing the load-carrying capacity and the friction torque. So, the proposed control systems were designed and tested under the conditions of limited lateral shaft displacements and action of a random external force. The tests were performed using simulation models of a controlled rotating machine in MATLAB. The rotating machine simulation model includes modules of the rigid shaft, the coupling with linear axial reaction, and the conical bearing. The bearing module is based on the numerical solution of the generalized Reynolds equation and its non-linear approximation with fully connected neural networks. The obtained results demonstrated that the application of an adaptive PI controller or a DQN agent allows decreasing friction torque in a bearing under the conditions of a random external force. The goal of a DQN agent is self-learning in contrast to an adaptive PI controller that needs to be tuned.

Tribological behavior of dimples textured rolling element bearings under stepped load and starved lubrication

Abstract: Purpose The purpose of this paper is to report the tribological behavior of dimples textured rolling element bearings (REBs) under variable load and starved lubrication. Design/methodology/approach The pattern parameters include line-diameter of dimples (200 µm, 250 µm, 300 µm), depth of dimples (10 µm, 20 µm, 30 µm). Dimple patterns were prepared on the raceways of the shaft washers of cylindrical roller thrust bearings (CRTBs). A vertical wear test rig was used to obtain their coefficients of friction (COFs) under stepped load (1200–6000 N, with a manually increase of 1200 N every 3600 s) and starved lubrication. The wear losses and worn surfaces were characterized. The tribological performance between stepped load and fixed load (4000 N) was compared. The influence mechanism of dimples on the friction and wear properties of CRTBs under stepped load and starved lubrication was also discussed. Findings Compared with the data of smooth ones, the average COFs of the dimples textured bearings are almost all reduced under stepped load and starved lubrication, while their mass losses almost all get higher. The depth−diameter ratio and the effective volume coefficient of dimples are the important factors. In this work, compared with the smooth group, when the line-diameter of dimple is 250 µm and the depth is 20 µm, i.e. the depth−diameter ratio is 0.08, its average COF is reduced by 46.8% and its mass loss is reduced by about 7%, showing wonderful friction-reducing effect and good wear resistance. Originality/value This work can provide a reference for the raceway design of REBs.

Numerical Wear Modeling in the Mixed and Boundary Lubrication Regime

Abstract: The increasing use of low-viscosity lubricants in order to reduce the friction in machine elements such as rolling bearings is leading to increased operation in the mixed or boundary lubrication regime. The associated wear can lead to an earlier failure of tribological systems. In this context, a detailed wear simulation offers great potential with regard to the design of machine elements as well as the calculation of lifetimes. This contribution presents an approach for the numerical wear simulation of lubricated rolling/sliding-contacts. Therefore, a finite element method-based simulation model was developed which is able to deal with non-Gaussian surfaces and contacts subject to boundary and mixed lubrication. Using the example of an axial cylindrical roller bearing considering realistic geometry, locally varying velocities, and two load cases, the wear modeling results of the mixed and the boundary lubrication regime were illustrated. The wear coefficient required for Archard’s wear model was determined experimentally by means of a two-disc tribometer.

Application of physics-informed neural network in the analysis of hydrodynamic lubrication

Abstract: Abstract The last decade has witnessed a surge of interest in artificial neural network in many different areas of scientific research. Despite the rapid expansion in the application of neural networks, few efforts have been carried out to introduce such a powerful tool into lubrication studies. Thus, this work aims to apply the physics-informed neural network (PINN) to the hydrodynamic lubrication analysis. The 2D Reynolds equation is solved. The PINN is a meshless method and does not require big data for network training compared with classical methods. Our results are consistent with those obtained by experiments and the finite element method. Hence, we envision that the PINN method will have great application potential in lubrication and bearing research.

Analysis of Dynamic Characteristics of Small-Scale and Low-Stiffness Ring Squeeze Film Damper-Rotor System

Abstract: Rotor machinery supports are susceptible to fracture arising from multi-period or irregular transient vibration and even the inconspicuous fatigue phenomenon. The novel dynamic model of a rotor mounted on the floating ring squeeze film damper (SFD) was developed. The proposed SFD implements low stiffness and small scale to overcome the deficiency. Based on the theory of hydrodynamic lubrication, the Reynolds equations on the working principle of the floating ring are established. Then, the dynamic characteristics of the rotor system during maneuvers, with the floating ring SFD supports, are subsequently examined by adopting the finite difference method. In addition, the oil film whirl mechanism of the floating ring SFD is demonstrated according to the transient analysis of the fluid–structure interaction model. The results of the SFD simulation reveal that, with increasing eccentricity ratio, both the inner and outer oil film pressure tend to be larger due to the shrinkage of the effective coverage of oil film. The maximum oil film pressure and bearing capacity increase nonlinearly within a certain eccentricity ratio range. Through the comparisons of the results, the vibration suppression effects of the proposed SFD are analyzed. This work will provide the practical reference for the dynamic design of the rotor support system.

Influence of Structural and Operating Parameters on Lubrication Performance of Water-Lubricated Polymer Bearing with Journal Misalignment

Abstract: Marine water-lubricated polymer bearings support the propeller shaft that stretches out of the ship. The bending deformation of propeller shaft often leads to journal misalignment, significantly impacting the bearing performance. In this paper, a mixed lubrication model for water-lubricated polymer bearing is established considering the effect of journal misalignment, liner elastic deformation, and local turbulence. The influence of key structural and operating parameters on the performance of water-lubricated bearing with journal misalignment is investigated. The results show that the journal misalignment significantly reduces the load-carrying capacity, deteriorates the bearing tribological characteristics, and may cause different axial sections of the bearing to be in different lubrication regimes. Compared with aligned bearings, increasing the length–diameter ratio to improve the load-carrying capacity is significantly weakened for misaligned bearings. Increasing the liner thickness and the load improves axial uniformity of pressure distribution of misaligned bearings. A relatively large clearance ratio decreases the load-carrying capacity and increases the friction coefficient of bearings in the mixed lubrication regime.