Lubricating Oil Film Research Articles

Dynamic Analysis of Radial Journal Bearing-Rotor System Based on the Meshless Barycentric Rational Interpolation Collocation Method

This study focuses on a rigid rotor supported by radial journal bearings. Initially, models for the unsteady oil film force in bearing lubrication and the dynamics of the bearing-rotor system are established. Subsequently, the Reynolds equation for dynamic lubricating oil films is discretely solved using the meshless barycentric rational interpolation collocation method. By combining this with the equation of motion for the axis orbit, the oil film pressure distribution, the dynamic response of the rotor, and the axis orbit are calculated. Furthermore, the study investigates the dynamic response of the rotor at different rotational speeds, both with and without considering unbalanced loads. Finally, the influence of step load on the stability of rotor motion is analyzed, revealing that applying an appropriate step load to the rotor can effectively mitigate the lubricating oil films oscillation conditions. The findings of this study hold significant reference value and practical utility for engineering applications.

Kinematics Analysis and Oil Film Lubrication Characteristics in the Piston–Cylinder Interface of a Bent-Axis-Type Piston Motor

Hydraulic piston motors are characterized by their excellent starting performance, high transmission torque, good sealing performance, compact design, and lightweight. These attributes make them highly applicable in fields such as construction machinery and marine applications. With the advancement of hydraulic transmission technology, higher performance requirements have been set for hydraulic motors. While extensive research has been conducted on hydraulic pumps, studies focusing on the performance of hydraulic motors remain relatively limited. Therefore, this paper is novel in that, based on the motion and force conditions of the piston, it differs from previous research on swashplate-type machinery by considering the complex structure of the bent-axis motor; it employs a micro finite element method to analyze the oil film characteristics at the piston–cylinder interface in a bent-axis piston motor, the structural changes in the piston assembly in the bent-axis motor are comprehensively considered, and a fluid–structure coupling model for the piston–cylinder interface is established. The leakage and viscous friction power loss equations for the piston–cylinder interface are derived. Simulation analyses are conducted using MATLAB R2016a to reveal the variation patterns of leakage and viscous friction power loss under different operating conditions and structural parameters, providing valuable insights for the operation analysis, energy loss evaluation, structural design optimization, and engineering applications of bent-axis piston motors.

Transient lubrication of floating bush coupled with dynamics and kinematics of cam-roller in fuel supply mechanism of diesel engine

The roller-floating bush pin is a major component in the fuel supply mechanism of a diesel engine, and its tribological performance seriously affects the reliability of the equipment. In this study, a transient thermoelastic hydrodynamic lubrication analysis model of the double-layer oil film on the roller-floating bush pin is established, which is coupled with the dynamic and kinematic analysis model of the cam-roller. The transient dynamic characteristics, such as time-varying speeds and loads of the roller during the operation of the cam, were considered. Also, the elastic deformation and the thermal effect were considered in the lubrication model. The relevant experimental platform for this double-layer oil film lubrication structure was built, and the simulation model was verified through experiments. The influence of the operating conditions, including cam speed and plunger fuel pressure, on the lubrication performance of the structure is explored, and besides, the influence of the structural parameters, including length-diameter ratios and clearance ratios, is also analyzed. It shows the lubrication condition of the inner oil film is worse compared with the outer oil film. As the explored factors change, the pressure of the inner oil film is more affected than that of the outer oil film. This work could provide useful guidance in designing the roller-floating bush pin in the fuel supply mechanism.

Occlusion failure analysis and optimization design for steel piston pin hole-pin friction pair

The focus of the present study was on the D25TCIF steel piston, and the underlying causes of pin hole occlusion failure were systematically analyzed. The investigation considered factors such as heat transfer, mechanics, lubrication, material properties, and forging processes. Additionally, an optimization strategy was introduced based on the cause of the failure to reduce the risk of occlusion failure of the pin hole. At the same time, the influence of the structural parameters of the connecting rod small head on the lubrication performance of the pin hole bearing was investigated, providing a theoretical basis for the matching design of the structural parameters of the double friction pair of the piston pin bearing. The findings indicate that the primary cause of pin hole occlusion failure in steel pistons is the concentration of thermo-mechanical coupling stresses and elevated temperatures within the pin hole. This condition results in the rupture of the lubricating oil film in the pin hole bearing, leading to dry friction between the piston pin and the bearing surface. The optimization method designed in the present study enhanced the minimum oil film thickness of the pin hole bearing from 0.354 μm to 0.377 μm, reflecting an increase of 6.50 %. Additionally, the minimum oil film thickness of the small head bearing was improved from 0.599 μm to 0.691 μm, corresponding to a 15.36 % increase compared to the original configuration. Meanwhile, the optimization method predicted a minimum oil film thickness of 0.382 μm for pin hole bearings and 0.693 μm for small-head bearings, with a relative error of less than 5 % from the simulated values. Such findings demonstrate that the optimization method has a good optimization effect and accurate prediction. This approach offers novel insights for the development of future solutions to address the failure of steel pistons in engineering applications.

Slippery liquid-infused porous surfaces for high-performance moisture-responsive actuators

Smart actuators convert environmental changes into mechanical energy. However, the actuation performance and robustness of smart actuators are limited by the weak interlaminar force and poor adhesion between layers. Herein, we report moisture-responsive actuators integrated with slippery liquid-infused porous surfaces (SLIPSs). The difference in adsorption capacity of water molecules further increases because the SLIPS layer is isolated from air by the lubricating oil film. Compared with the initial (graphene oxide/candle soot, GO/CS) bilayer film, the integrated SLIPS layer improved the bending performance by 12.6% and shortened the response–recovery time by one-third. Moreover, the GO/SLIPS actuator exhibited excellent long-term stability over 10 000 cycles due to the lubricating oil's capillary fluidity. In addition, a moisture-controlled water-transport device based on a GO/SLIPS film was demonstrated.

Enhancing wind turbine energy efficiency: Tribo-dynamics modeling and shape modification

The performance of wind turbine gearbox planetary bearing systems directly influences the turbine's reliability, energy production efficiency, and economy. However, the lack of a comprehensive model to accurately predict the dynamic meshing load of helical gears and temperature effects hinders a deeper understanding of the transient performance of gearbox planetary sliding bearings. Additionally, research on shape modification for gearbox planetary sliding bearings remains inadequate. This study develops a comprehensive tribo-dynamics model that considers the dynamic meshing forces of helical gears and temperature effects. The model's effectiveness is validated by the concordance between experimental data from a full-size test bench and simulation results on oil film thickness and temperature. Transient simulation analysis indicates insufficient lubrication, high-temperature rise, and severe contact that reduce electricity production efficiency and reliability, all of which occur at bearing axial edges. Therefore, three modified bearing designs (super-elliptical, trapezoidal, and quadratic shapes) are introduced, and their improved performance is thoroughly compared. The super-elliptical design increases the minimum oil film thickness by 2.60 μm. The trapezoidal design reduces cumulative friction energy losses by 4.34 %. Each modified design successfully reduces the edge wear and oil temperature. The underlying enhancing mechanisms are revealed to be oil film uniform redistribution and lubrication states' alteration. This work can contribute to the reliability, electricity production efficiency, and economy of global wind turbines and support the achievement of net-zero emission goals.

Study on lubrication characteristics of multi-layer structure hinge under the influence of clearance dynamic

This paper presents a methodology for investigating the lubrication characteristics of multi-layer structural mechanical hinges based on clearance dynamics. By multi-layer hinged structures, we mean the four mediums: the journal, lubricating oil film, bearing sleeve, and connecting rod. Initially, a dynamic model that incorporates clearance is established using the automatic dynamic analysis of mechanical systems, revealing that the primary contact area is located between 50° and 70°. Subsequently, a lubrication model for the multi-layer structural mechanical hinge is constructed using ANSYS FLUENT software, which demonstrates the effects of critical parameters—such as contact angle, sleeve installation angle, inlet pressure, and shaft neck speed—on lubricant flow, pressure, and void fraction. The findings indicate that the motion offset angle significantly influences the pressure distribution within the oil film area, with high-pressure and low-pressure zones oriented counterclockwise and clockwise, respectively, relative to the offset angle axis. Furthermore, as the distance between the offset angle and the oil inlet increases, the volume fraction of cavitation decreases from 1.77% to 1.16%. When the sleeve installation angle aligns with the motion offset, the volume fraction of cavitation reaches 1.9%. Conversely, when the assembly angle aligns the oil inlet hole with the injection hole, the volume fraction of cavitation is minimized to 0.36%, resulting in an approximate performance improvement of 81.11%. This study provides a theoretical foundation for optimizing the lubrication design of multi-layer structural mechanical hinges and offers substantial guidance for the lubrication of mechanical hinges.

Study on oil film spreading characteristics on the jet lubricating tooth surface of aviation herringbone gear

Purpose During the oil lubrication process of aviation herringbone gears, lubricating oil is injected into and spreads around the tooth surface. Its spreading characteristics directly affect the lubrication state and transmission efficiency of gears. This study aims to investigate the effect of changing the injection parameters and gear operating conditions on the oil film deposition during injection lubrication. Design/methodology/approach The computational fluid dynamics method was used to establish the computational domain for the simulation and optimization using an orthogonal test. The oil film spreading and thickness of the tooth surface were calculated with the change in gear speed, fuel injection distance and fuel injection speed. Optimized oil injection lubrication parameters were obtained, and design ideas were provided for the oil injection lubrication analysis of aviation herringbone gears. Findings Under different operating conditions, such as varying the injection speed, gear rotational speed and injection distance, there were differences in the distribution of the lubricating oil film formed on the tooth surface. The thickness of the oil film decreases as the distance from the injection port increases. The thickness of the oil film deposition can be increased by increasing the injection velocity and reducing the gear rotation speed. The injection distance had a relatively small effect on the spreading thickness of the deposited oil film, affecting only the dynamic spreading process of oil film deposition. Furthermore, the simulation results are compared with the analytical calculation results, and finally the experimental verification is carried out. Originality/value Oil spray lubrication characteristics are important for achieving precise gear lubrication designs in the aerospace field. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2023-0250/

Effect of surface square textures on the physical field of static and dynamic pressure thrust bearings and multi-objective optimization

PurposeThe lubrication performance of static and dynamic pressure thrust bearings is improved by introducing texture on the sealing edge.Design/methodology/approachThrough model building, meshing and boundary condition setting, the influence of square texture on oil film lubrication performance was simulated and analyzed, and an improved algorithm was applied to perform optimization of lubrication performance.FindingsThe findings of this study reveal that the optimum lubrication performance is attained when adjusting the parameters of the square texture to 0.12 mm, 0.1 mm, 1 mm and 34 mm. In such circumstances, the thrust bearing with square textures demonstrates an increase in loading capacity of around 19% and a temperature reduction of about 2ºC compared to a smooth thrust bearing.Originality/valueThe original Reynolds equation is revised, and the influence of square texture on the physical field of oil film is analyzed, considering the turbulence state and cavitation phenomenon. The multi-objective function under square texture parameters was established using BP neural network, and the improved multi-objective salp swarm algorithm was used to optimize the process parameters.

Application Study of Acoustic Reflectivity Based on Phased Array Ultrasonics in Evaluating Lubricating Oil Film Thickness

Bearings play a key role in rolling mills, and the uniformity of their lubricant film directly affects the degree of wear of bearings and the safety of equipment. Due to long-term stress, the lubricant film inside the bearing is not uniformly distributed, resulting in uneven wear between the journal and the shaft tile, which increases the potential safety hazards in production. Traditional disassembly inspection methods are complex and time-consuming. Ultrasonic nondestructive testing technology, which has the advantages of nondestructive and adaptable, has become an effective means of assessing the thickness of the oil film in bearings. In this study, an experimental platform for calibrating the lubricant film thickness in bearings was constructed for the first time, and the acoustic characteristics of different thicknesses of the oil film were measured using ultrasonic detection equipment to verify the accuracy of the simulation process. The experimental results show that after discrete Fourier transform processing, the main features of the frequency channels of the reflected acoustic signals of different thicknesses of the oil film are consistent with the finite element simulation results, and the errors of the oil film thicknesses calculated from the reflection coefficients are within 10% of the set thicknesses, and the measurement ranges cover from 5 μm to 250 μm. Therefore, the above method can realize the accurate measurement of the thicknesses of the oil film in bearings.

Partial abrasion modeling and variable load characteristics analysis for high-speed load sensing electro-hydrostatic actuator pump of aircraft

The load-sensing electro-hydrostatic actuator (LS-EHA) allows to reduce the thermal output and enhance the dynamic characteristics of the more electric aircraft (MEA). In addition, the forecasting of the LS-EHA is crucial for its efficient functioning. This study proposes a novel model for the analysis of overturning and wear characterization of the slipper, while focusing on the partial abrasion. The transient thermoelastic hydrodynamic (TEHD) lubricating analysis of the slipper pair is solved by an analytical model along with the finite difference method. In the proposed partial abrasion model, the non-uniformity of the oil film thickness and the partial abrasion contour for the slipper bottom surface are considered through the discrete friction area approach in order to reach a higher precision. Afterward, the overturning behavior characteristics of the slipper and the variation law in its overturning behavior under different rotation speeds, load delivery pressures, and swashplate angles are analyzed. The obtained results demonstrate that the lubricating oil film field is unevenly distributed, and the overturning behavior of the slipper has certain variable load characteristics. Finally, the effectiveness and precision of the proposed partial abrasion model are validated through comparative simulation experiments and analysis.

Multiscale study on the solid-liquid synergistic lubrication mechanism of graphite and liquid lubricant in polymer composites

Solid-liquid synergistic lubrication, in combination with the advantages of solid and liquid lubrication, has gained the great popularity in recent years. However, the mechanism of solid-liquid synergetic lubrication is still unclear. In this paper, graphite and poly α-olefin base oil (PAO) were used as self-lubricating additives to evaluate their synergistic effect. The results show that the composites possess good mechanical and excellent tribological properties with a nanoindentation modulus of 3.8 GPa, a coefficient of friction of 0.0998, as well as a wear rate of 1.3 × 10−14 m3/N·m. Both transfer film and lubricating oil film exist on the friction interface, and the lubricating oil film protects the counter ball from excessive oxidation. At the same time, with combination of molecular dynamics (MD) simulation and first-principles calculations, the synergistic lubrication mechanism of graphite and PAO was manifested. PAO destroyed the interlayer structure of graphite, making it easier to form a transfer film on the counter ball surface. The weak chemical bond between graphite and PAO facilitates more PAO molecules to gather at the interface while forming the transfer film, which benefits the formation of lubricating oil film. The synergistic effect of graphite and PAO molecules is critical in promoting the further reduction of COF.

Oil-Loaded Mesoporous Silica to Enhance the Lubrication of Polypropylene Resin Composite Materials

Polymer self-lubricating materials have advantages such as low friction coefficient, good wear resistance, and high work efficiency, giving them wide application potential in friction and wear. This work fabricated polymer-based self-lubricating materials by incorporating oil-loaded mesoporous silica nanoparticles (MSNs + YR1800) in the polypropylene resin (PP). The effects of different content of MSNs + YR1800 on the tribological and mechanical properties of the obtained self-lubricating composite materials were studied. The results indicate that the content of MSNs + YR1800 in composite materials significantly impacts their tribological properties. When the content of MSNs + YR1800 was 10 wt%, the coefficient of friction reduced to 0.09,which was 84.5% lower than for PP and 78.6% lower than for composite materials containing 5 wt% mesoporous silica nanoparticle (MSNs). Compared with pure PP, the wear rate decreases from 4.93 × 10−11 m3∙Nm−1 to 4.43 × 10−13 m3∙Nm−1, which is reduced by two orders of magnitude. The excellent tribological properties of composite materials are attributed to the high specific surface area, large pore volume, strong adsorption capacity, and high oil loading capacity of mesoporous silica nanoparticle as nanofillers. The MSNs + YR1800 release lubricants to form a lubricating oil film during the friction process under load conditions, preventing direct contact between the friction pair and the surface of the composite material. Compared with polymer-silica hybrid oil-loaded microcapsules, MSNs + YR1800 can effectively reduce lubricant leakage, prolong operation life, improve lubrication efficiency, and ensure the continuous and stable existence of lubricating oil films.

Reviewing experimental and theoretical efforts and key findings regarding hydrodynamic journal bearing geometry

Abstract Journal bearing operation particularly in regard to marine applications is significantly affected by the performance of the most critical operational factors. Specifically, the lubricating oil film within journal bearing is so often than not subject to hazardous deterioration and ultimate failure in real operating conditions. Considering such fact, the current study is intended to carry out a literature survey regarding the efforts towards enhanced journal bearing performance based on proper selection of geometrical design for journal bearing. The aggregated data were thoroughly analyzed and assessed utilizing experimental, theoretical as well as numerical means. The outcomes derived from the conducted review represent firm grounds for carrying out extensive modifications into journal bearing design for marine applications. Further, such data will possibly be employed in future research investigations to extend the capability of journal bearing and its functions to attain the most possible enhanced performance in actual operating conditions. Apparently, the vast majority of both experimental and theoretical studies into journal bearing geometrical designs for enhanced performance, 66 in all, have been focused on surface texture accounting for 26.67 % (29 research studies) and 32.43 % (33 research studies) of the total investigations under study respectively. Regarding the experimental studies, realizing promoted performance of lubricating oil film by working on pressure profile has evidently obtained the largest contribution representing 35.5% of the overall bulk of the reviewed efforts, Figure 6.

Hierarchical design of microcapsules-based epoxy resin coating enhanced with Ti3C2Tx for improving thermal, tribological, anti-corrosive performance

Self-lubricating coating has sparked significant research interest due to its remarkable tribology performance. However, traditional microcapsules-based self-lubricating coating still faces challenges in long-term serviceability and poor anti-corrosion performance. In this paper, a novel self-lubricating epoxy resin coating was proposed based on hierarchical design and energy wear theory. Microcapsules (MC) containing Polyalphaolefin (PAO40) were prepared via the solvent evaporation approach. Ti3C2Tx MXene (T) with high thermal conductivity was then incorporated into the MC-enhanced epoxy resin coating (EP) to construct the novel self-lubricating EP coating (T-MC-EP). Compared to the EP coating, the thermal conductivity of the T-MC-EP coating increased by 79.4%. Finite element analysis indicated that T constructed thermally conductive network in the coating, serving as the main heat carrier. Furthermore, the wear rate decreased by 91.2%, primarily attributed to the formation of lubricating oil film during friction and the reduction of epoxy resin molecular oxidation fracture caused by friction heat. After 31 days of salt spray testing, the T-MC-EP coating also exhibited superior anti-corrosion performance. This work provides an innovative insight into designing multifunctional coating, including excellent mechanical, thermal, tribological, and anti-corrosive performance.

Analysis of oil film flow characteristics and lubrication performance of thrust bearing of 1000MW Hydraulic Turbine Unit

Abstract Hydro-generator unit is the core component of the hydropower station, and the stability of the shaft system directly determines the safety of the hydropower station. Thrust bearing is the only component to bear axial load, and working performance directly affects the stable operation and efficiency of the unit. In this study, a full 3D model of the shaft system of a 1000 MW hydro-generator unit is established, and the oil flow of thrust bearing oil film and oil in the oil tank considering the spray system and the overall model is analysed by means of the thermo-hydrodynamic method. The results show that the load increases with increasing inclination angle. Within certain limits, the pressure and temperature of the oil film increase with increasing inclination. And there are many vortices in the tank. Although the spray system reduces the oil churn, the lubricating oil flow between pads is chaotic. The loss is mainly caused by the chaotic flow between pads. Analyzing the effects of oil film thermal effects on bearing loads, lubricant flow, and bearing surface temperatures of tilting pads provides valuable insights for bearing design and maintenance guidance.

A Synchronous Sensing Method of Measuring Lubricating Oil Film Thickness and Temperature by Using Eddy Current Effect

A Synchronous Sensing Method of Measuring Lubricating Oil Film Thickness and Temperature by Using Eddy Current Effect

Hydrostatic bearing groove multi-objective optimization of the gear ring housing interface in a straight-line conjugate internal meshing gear pump

The lubrication performance of a straight-line conjugate internal meshing gear pump is poor under the low-speed, high-pressure operating conditions of the volumetric servo speed control system, and it is difficult to establish a full fluid lubricating oil film between the gear ring and the housing. This leads to significant wear and severe heating between the gear ring and the housing. The lubrication performance of the interface moving pair of the electro-hydraulic actuator pump gear ring housing can be improved by designing a reasonable lubrication bearing structure for the gear ring housing. In this study, a multi-field coupling multi-objective optimization model was established to improve lubrication performance and volumetric efficiency. The whole model consists of the dynamic model of the gear ring components, the fluid lubrication model of the gear ring housing interface, the oil film formation and sealing model considering the influence of temperature, and the multi-objective optimization model. The comprehensive performance of the straight-line conjugate internal meshing gear pump was verified experimentally using a test bench. The results show that the lubrication performance is improved, the mechanical loss is reduced by 31.52%, and the volumetric efficiency is increased by 4.91%.

Investigation of Surface Integrity of 304 Stainless Steel in Turning Process with Nanofluid Minimum-Quantity Lubrication Using h-BN Nanoparticles

This paper investigates the influence of the concentration and particle size of h-BN nanoparticles in a nanofluid on the surface integrity of 304 austenitic stainless steel during turning, focusing on the cutting force, friction coefficient, cutting temperature, surface roughness, surface residual stress, work hardening capacity, and 3D surface topography. The results show that, compared to dry cutting, the addition of 3 wt.% h-BN nanofluid can reduce the friction coefficient on the rake face by 38.9%, lower the cutting temperature by 43.5%, decrease the surface roughness by 53.8%, decrease the surface residual stress by 61.6%, and reduce the work hardening degree by 27.5%. Two-dimensional profiles and the 3D surface topography display a more balanced peak–valley distribution. Furthermore, by studying the effect of different h-BN particle sizes in nanofluids on the surface integrity of the machined workpiece, it was found that nanoscale particles have a greater tendency to penetrate the tool–chip interface than submicron particles. Moreover, the h-BN particles in the nanofluid play a “rolling effect” and “microsphere” effect, and the sesame oil will also form a lubricating oil film in the knife-chip contact area, thereby reducing the friction coefficient, reducing the cutting force, and improving the machining surface quality.

Research on Prediction Methods for Eccentric Wear of the Slipper Pair in Axial Piston Pumps and Lubrication Performance Analysis

Abstract The axial piston pump (APP) is the core power component of hydraulic systems. Its friction pair wear can cause the degradation of piston pump performance until the function is completely lost or the service life is terminated. The slipper pair, prone to wear failure, is selected as the research object in this paper. The prediction method for the eccentric wear of the slipper pair is established, and the gradual change rules of the performance with wear accumulation are explored. The micro-surface rough peak contact and the stress state of the slipper pair are analyzed, and the mixed lubrication model of the slipper pair is established based on the elastohydrodynamic lubrication (EHL) model of the slipper pair. Grid discretization of a sealing belt of the slipper pair is carried out based on two-body abrasive wear and Archard adhesive wear models to improve the prediction method for eccentric wear of the slipper pair. The effectiveness of the proposed method is verified by a surface morphology analysis of the worn slipper. The results showed that the wear depth and wear width of the outer edge of the slipper bottom surface are positively correlated with the oil discharge pressure and the inclination angle of the swashplate, and negatively correlated with the rotational speed and the dynamic oil viscosity. The outer edge of the slipper is wedged after eccentric wear, and the hydrodynamic effect of the lubricating oil film of the slipper pair is enhanced. Hence, proper wear can improve the lubrication performance of the slipper pair.