Lubrication Analysis Research Articles

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.

Lubrication Analysis of a Mechanical Seal Considering the Mixed Lubricant State of Gas and Liquid During External Power Shutdown of a Reactor Cooling Pump

Lubrication Analysis of a Mechanical Seal Considering the Mixed Lubricant State of Gas and Liquid During External Power Shutdown of a Reactor Cooling Pump

A heat transfer model for thermal distortions in high speed spiral groove gas lubricated face seals

The thermal distortions of seal face caused by heat transfer directly affect the stability of seal operation. Here, a heat transfer analysis model of spiral groove gas face seal is established taking account of gas compressibility and choked flow effect. Then, a thermoelastohydrodynamic lubrication (TEHL) analysis is carried out based on the proposed heat transfer model, frictional heat flux, surface conduction heat flux, and film adsorption heat flux are calculated, and face distortions are also analyzed under different operating parameters including rotational speed, seal temperature and seal pressure. It is shown that, the adsorption heat induced by gas expansion makes the film cooling, which often leads complex temperature distributions and plays an important and non-ignored role in thermal distortions. For the spiral groove face seal, the increase of seal pressure and rotational speed makes the adsorption heat increase significantly due to pumping effect of grooves. The more important is that the thermal distortions may be controlled by changing seal width. Here, for the spiral groove face seal, the clearance can transfer divergent to convergent with increasing seal width from 5 mm to 13.1 mm. This provides a potential way for distortion control in gas face seal design.

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/

Enhanced PINNs with augmented Lagrangian method and transfer learning for hydrodynamic lubrication analysis

PurposeBy seamlessly integrating physical laws, physics-informed neural networks (PINNs) have flexibly solved a wide variety of partial differential equations (PDEs). However, encoding PDEs and constraints as soft penalties in the loss function can cause gradient imbalances, leading to training and accuracy issues. This study aims to introduce the augmented Lagrangian method (ALM) and transfer learning to address these challenges and enhance the effectiveness of PINNs for hydrodynamic lubrication analysis.Design/methodology/approachThe loss function was reformatted by ALM, adaptively adjusting the loss weights during training. Transfer learning was used to accelerate the convergence of PINNs under similar conditions. Additionally, the iterative process for load balancing was reframed as an inverse problem by extending film thickness as a trainable variable.FindingsALM-PINNs significantly reduced the maximum absolute boundary error by almost 80%. Transfer learning accelerated PINNs for solving the Reynolds equation, reducing training epochs by an order of magnitude. The iterative process for load balancing was effectively eliminated by extending the thickness as a trainable parameter, achieving a maximum percentage error of 2.31%. These outcomes demonstrated strong agreement with FDM results, analytical solutions and experimental data.Originality/valueThis study proposes a PINN-based approach for hydrodynamic lubrication analysis that significantly improves boundary accuracy and the training process. Additionally, it effectively replaces the load balancing procedure. This methodology demonstrates considerable potential for broader applications across various boundary value problems and iterative processes.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2024-0277/

Transient mixed thermal elastohydrodynamic lubrication analysis of aero ball bearing under non-steady state conditions

A transient mixed thermal elastohydrodynamic lubrication model of bearing considering the thermal effect and the changes in velocity, load, and contact geometry is proposed. Based on the bearing dynamic and lubrication analysis, the effects of bearing rotational speed and start-stop conditions on the dynamic behavior and lubrication performance are studied. Results show that when the bearing rotational speed exceeds a certain critical value, the increasing speed will reduce the film thickness, especially the outer raceway. The increasing bearing acceleration can cause a higher slide-roll ratio and film temperature at the initial start-up process. Compared with the start-up process, the lubrication change in the shut-down process has a similar opposite trend, but the overall lubrication performance is better.

Multi-Physical Field, Coupled, Mixed Lubrication Analysis of Hydraulic Reciprocating Vacuum Lip Seal

Engineering practice has demonstrated that seal failure can result in severe leakage and wear, reducing the efficiency of hydraulic systems and even leading to major safety risks. Currently, analyses of the thermal aspect of seal interfaces are relatively limited, with most studies focusing on mechanical analysis. However, in actual applications, temperature has a significant impact on sealing performance. In this paper, nonlinear elastomechanics, viscous fluid mechanics, micro-contact mechanics, micro-deformation theory, and thermodynamics are coupled to establish a mixed lubrication model considering the thermal effect. The reliability of the mixed lubrication model is verified through experiments, and the temperature distribution of the oil film in the sealing area and the temperature distribution of the seal ring are simulated. Finally, the effects of the reciprocating speed, root mean square roughness, fluid medium pressure, and seal pre-compression on seal friction force and leakage are investigated. The results show that the heat generated in the sealing area accumulates at the bottom of the V-ring. Under the same conditions, compared with the instroke, the temperature-rise area of the outstroke is biased to the left and the increase in temperature is greater. In addition, the piston rod speed and the preliminary compression of the seal ring have a greater impact on the overall seal friction force and leakage. Under a lower seal pre-compression, the RMS roughness has a great influence on the leakage and friction in the outstroke, while the impact of the internal stroke is limited.

Analysis and Prospects of Lubrication and Friction Characteristics in Cold Strip Rolling: A Review

Lubrication and friction are the core processes in cold strip rolling, which are the key links to realizing the stable production of high‐quality strips, reflecting country advanced level in rolling technology. This review investigates the crucial properties of lubrication and friction in cold strip rolling by analyzing the mechanism, characterization methods, and influencing factors. The lubricant forms an oil film on the surface of rolls and strips based on the lubrication dynamics and tribology theory, changing the asperity contact state in the loaded roll gap, leading to changes in friction characteristics. Oil film thickness and coefficient of friction (COF) are crucial parameters for characterizing and judging the characteristics of lubrication and friction, theoretical calculations have become the core analytical method, and the study of the measurement method is still a great challenge. Parameters like rolling speed and oil viscosity affect the lubricant distribution and asperity contact in the loaded roll gap, changing the lubrication and friction state. The influence of parameters is strongly linked to the experimental or rolling environment. Prospective research trends on lubrication and friction in cold strip rolling are presented based on the status of research on lubrication and friction characterization.

Optimization of high-speed reducer in electric vehicle based on analysis of lubrication

PurposeThe purposes of this paper are optimization of high speed reducer in electric vehicles based on the analysis of lubrication and verification of simulation accuracy and optimization results.Design/methodology/approachThe traditional CFD method presents poor applicability to complex geometric problems due to grid deformity. Therefore, moving particle semi-implicit (MPS) method is applied in this study to simulate lubrication of the reducer and analyze the influence of input speed and lubrication system design on the distribution. According to the results, the reducer is optimized. Meanwhile, the experiments for lubrication and churning power loss is carried out to verify the accuracy of simulation and optimization effects.FindingsThe flow field of lubricant inside the reducer is obtained. The lubrication system of reducer needs to be improved. Simulation and experiment show that the optimization is sufficient and efficient.Originality/valueAccording to the simulation of lubrication, the reducer is optimized. The lubrication experimental setup is established. The conclusion of paper can provide the method and tool for reducer in electric vehicle.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-04-2024-0123/

Unified gear tribo-dynamic of transient mixed lubrication and nonlinear dynamics and its experimental validation

The rapid development of electric drives technology presents new challenges in the domain of vibration and noise suppression within gear trains. Dynamics modeling serves as a crucial method for studying vibration and noise; however, a deficiency exists in adequately considering the interaction between tribology and the dynamics of gear drives in current research endeavors. This article proposes a unified tribo-dynamic approach to facilitate a more realistic and accurate linkage analysis of transient mixed lubrication, friction, flash temperature, stiffness, backlash, and dynamics in gear drives. The TPMD approach is proposed to reduce convergence elapsed time. The meshing stiffness and backlash under transient mixed lubrication are developed and used as additional crucial bridges for the interactions in tribo-dynamic, supplementing the traditional consideration of friction. Gear vibration tests are carried out in both LOA and OLOA directions to validate the accuracy of the proposed model. Comparative analyses with conventional models highlight the advancements of the proposed model. The lubricated meshing stiffness, influenced by the combined effects of dynamics and tribology, exhibits characteristic fluctuations and is significantly lower than the Hertzian meshing stiffness. Tribological characteristics in tribo-dynamic differ notably from quasi-static conditions due to gear vibrations. The proposed tribo-dynamic model reveals higher DTE and vibration in the LOA direction compared to traditional dynamics. The intricate effects of friction, meshing stiffness, and backlash on vibration depend on factors like surface roughness, torque, and rotational speed.

Thermal elastohydrodynamic lubrication analysis of the roller enveloping hourglass worm drives considering the roller self-rotation behavior

Elastohydrodynamic lubrication (EHL) plays a crucial role in worm-drive tribology. However, in roller enveloping hourglass worm (REHW) drives, the unique rolling motion of the rollers reduces friction but presents challenges in accurately analyzing the film formation characteristics. To address this, a method for calculating the time-varying meshing characteristic parameters, considering the influence of the roller's self-rotation behavior, is proposed. A thermal EHL numerical model for REHW drives was established based on EHL theory by integrating these parameters. The lubrication characteristics at various meshing instants and contact positions were analyzed, and operational conditions and design parameters were identified to enhance lubrication performance. High-speed and heavy-load REHW drives have demonstrated superior lubrication performance. These findings provide theoretical guidance for optimizing lubrication performance and investigating wear in REHW drives.

Elastohydrodynamic lubrication analysis and temperature field simulation of gear system

Abstract The gearbox is one of the key components in the aero engine. In the process of high-speed operation, the internal temperature of the gearbox rises significantly, which seriously affects the service performance of transmission equipment. Based on the meshing principle and Herz contact theory, the basic meshing parameters are analyzed, and the comprehensive friction coefficient and heat flux are solved. According to the principle of convective heat transfer in a rotating disc and the frictional heat diffusion model, the CHTC (convective heat transfer coefficient) is analyzed. The FE model of the gear system is built based on ANSYS software, and the temperature distribution is analyzed by loading thermal boundary conditions with the APDL program. The calculation results indicate that the middle of the tooth tip or root of the gear has the maximum temperature. The research provides some reference values for the calculation method of the temperature field of the gear system under elastohydrodynamic lubrication.

Hydrodynamic lubrication analysis of curved conductive liquid conducting film at rail-armature interface

Hydrodynamic lubrication analysis of curved conductive liquid conducting film at rail-armature interface

Theoretical Model Development and Mixed Lubrication Analyses of Rolling Piston Type Rotary Compressors: A Review

Owing to the requirements for high performance and long life, the friction and wear problems of rolling piston type rotary compressors have drawn much attention. Various theoretical models have been developed and improved to reveal the inner state of the compressor and obtain the optimization schemes. However, there remain some disadvantages and research gaps in the corresponding modeling and mixed lubrication analyses, and a comprehensive summary is lacking. To have a better understanding of the research status, this paper reviews the theoretical model development and mixed lubrication analyses of the compressor in the past decades. The determination of compression pressure, the modeling process of moving components, and the key findings are presented in detail. On this basis, some important influencing factors and the problems remaining to be solved are also discussed. This paper provides multifaceted guidance for manufacturers and researchers to conduct further theoretical analysis and optimal design.

Applying Gaussian mixture models for enhanced characterization of featured surfaces and mixed lubrication analysis

Understanding surface topography is vital for optimizing the performance of engineering components. Featured surfaces, with distinct patterns and textures, have garnered attention for their potential to reduce friction and wear. However, accurately describing their topography poses challenges, necessitating effective segmentation methods in many applications. This paper proposes utilizing the Gaussian Mixture Model (GMM) clustering method as a novel approach for surface metrology analysis of featured surfaces. The GMM provides an approach to identify and analyze specific surface features and enhance comprehension of their contributions to functionality. The paper presents a comprehensive methodology involving surface characterization, GMM clustering, plateau reference plane location, and calculation of essential topography parameters. Results from four different surfaces are discussed, demonstrating the effectiveness of the proposed GMM-based methodology in segmenting plateau regions, grooves, and porosity.

Detectability of semen remained in a condom under various conditions

Some research has identified the prevalence and motivation of using condoms by assailants during sexual assault cases proving the necessity of analyzing condom trace evidence. The majority of the papers published have discussed forensic analysis of lubricants from condoms retrieved at sexual assault scenes but those discussing the identification of semen from condoms are rare. Therefore, the present study aims to provide insight into the detectability of the semen that remained in a condom, to examine the effect of exposure time, environmental conditions, and condom type, and ultimately to determine the capability of the AP test and Microscopic examination for identification of this sample type. In the study, samples were collected from three male donors after being instructed on the proper way of collecting the semen sample. The received samples from the donors were checked first by microscopic examination to observe the sperm to confirm that the sample being handled was semen. After confirmation, samples were transferred to 4 prepared condoms (brands: dkt xxx and Manforce) and kept in conditions i.e. two condoms in a refrigerator maintained from 2 to 10°C and other ones at ambient temperature (weather status: summer season of average 39°C). The samples were analyzed into two batches, the first analysis batch was conducted after the samples were exposed to the conditions within 11–60 days. After analysis from the first batch, the samples were continuously kept in the same condition for the consecutive second batch conducted when the samples reached 40–90 days. This study has determined that semen remaining in a condom can be detected and each test studied is appropriate according to the exposure stage, i.e., time and conditions of exposure. It has been found that nonmotile spermatozoa can be observed when semen remains in the condom for a few days. However, if the sample reaches approximately 25 days at room temperature above 25°C or 54 days below 10°C, the semen may dry out limiting the effectiveness of microscopic examination. Despite this, even semen that remained in a condom for up to 90 days can be identified by Acid Phosphatase. Results on condom type used reveal that condom constituents can crossreact with semen but none of them can limit the semen identification with Acid Phosphatase.

Numerical study of leakage rate in reciprocating seal with non-Gaussian topography characteristics using percolation mechanism

The topography significantly affects the leakage prevention of the sealing surface. However, the topography effect on sealing performance is not yet fully understood. The leakage mechanism cannot be revealed by average flow model using a statistical distribution to characterize the surface. This paper proposes a new leakage analysis method for reciprocating seals based on the percolation theory. The contact and lubrication analysis of non-Gaussian surfaces with different characteristics is conducted to establish three-dimensional percolation channels. The leakage rate can be calculated from the flow velocity across the cross-section at the critical constriction in the channel. The results show that compared with experimental data, the simulation results of the percolation model are more accurate than those of the average flow model.

Effect of Thermal Conductivity on Maximum Film Pressure in Point EHL Contact of Ceramics with Transverse Surface Roughness

Abstract Based on a fully flooded non-Newtonian transient thermal elastohydrodynamic lubrication analysis of representative engineering ceramics and a steel with different thermal conductivities and different surface roughness, it is clarified that material combinations leading to a reduction in the maximum film pressure can be found using the thermal conductivities of the contacting materials and the smooth surface temperatures of the same contacting materials. The results will make a significant contribution to the design of machine elements involving contact between materials of different thermal conductivity and surface roughness.

Analysis of isothermal elastohydrodynamic lubrication on the rough surface of a new type of trident universal joint

Analysis of isothermal elastohydrodynamic lubrication on the rough surface of a new type of trident universal joint

Application of back propagation neural network in the analysis of isothermal elastohydrodynamic lubrication

Developing stable and high precision solution methods has always been the most important research topic in the field of elastohydrodynamic lubrication (EHL). The emergence of artificial neural network(ANN) provide new ideas for the research of EHL solving methods. In this article, a model based on back propagation neural network (BPNN) is proposed to obtain the film thickness and pressure distribution of EHL. The model is established to predict the EHL characteristics with the data obtained from numerical calculation, and more numerical data are used to validate the results predicted by the ANN model. The orthogonal experimental method is utilized to tune model’s parameters. In addition, the method of increasing hidden layers is used to enhance the predictive ability of model. Finally, a double layer BPNN is completed that could predict oil pressure and film thickness accurately. And the exploratory research presented in this paper will provide a simple method for predicting lubrication behavior in industrial applications.