Lubrication Analysis Research Articles

Thermoelastohydrodynamic Mixed Lubrication of Combined Rod Seals Operating at High Pressures and Speeds: Mathematical Modeling and Numerical Analysis

Abstract Thermoelastohydrodynamic (TEHD) mixed lubrication characteristics of a step-combined rod seal under high-pressure and high-speed conditions are analyzed in this article. A novel TEHD mixed lubrication model for combined rod seals is innovatively established from the perspective of “seal-film-rod” system for the first time. Parameterized studies are conducted to evaluate the thermal effect on seal behavior with the comparison of isothermal elastohydrodynamic (EHD) lubrication analysis. Numerical results show that the interface friction heat is quite remarkable and mainly concentrated on the sealing lip, especially in high pressure and speed cases. With the increasing sealed pressure or rod speed, the temperature rise becomes more obvious and has a more significant impact on the sealing performance. The excessively rising temperature will even exceed the melting point of the sealing material, causing thermal damage.

Elastohydrodynamic Rotational Lubrication Analysis on the Multi-Body Dynamic Properties of Journal-Bearing Systems

This research aims to investigate the properties of elastohydrodynamic rotational lubrication analysis on journal-bearing systems. To simulate elastohydrodynamic lubrication on journal-bearing systems, the Elasto-Hydro-Dynamic (EHD) solver is combined with the Multi-Body Dynamic (MBD) solver to create MBD virtual environment with lubricant. The hydrodynamic lubricant is governed by using the Reynolds equation, whereas the elastic contact is governed using Greenwood and Tripp theories. The simulation is performed by changing the operating conditions such as the speed, load, and clearance between two surfaces. One can find these parameters’ effects such as film thickness, hydrodynamic pressure, and friction. The result shows that the friction induced by shaft speed is similar to the Stribeck curve on mixed lubrication regime. Consequently, the clearance, speed, and load will not only affect the friction but also affect the hydrodynamic pressure and film thickness.

Atomic spectrometry update: review of advances in the analysis of metals, chemicals and materials

This review covers advances in the analysis of advanced materials, metals, fuels and lubricants, nanostructures, ceramics, refractories, chemicals, catalysts and nuclear materials by a range of techniques including ICP-MS, non-destructive surface ablation and X-ray.

Comparative Economic Analysis and Investigation of Micro Lubrication Over Conventional Cooling in Manufacturing

Comparative Economic Analysis and Investigation of Micro Lubrication Over Conventional Cooling in Manufacturing

Study on the Dynamic Characteristics of Gears Considering Surface Topography in a Mixed Lubrication State

Based on mixed lubrication analysis, considering the influence of rough interface contact stiffness, contact damping, and interface friction on the gear transmission system, the relationship between interface contact and the overall performance of the gear transmission system has been established. First, the surface topography is characterized using statistical parameters of rough surfaces, and the contact stiffness and damping for tooth surfaces with different roughnesses are calculated. Subsequently, a six degree of freedom gear tribo-dynamics coupling model is developed. Finally, the established tribo-dynamics model is employed to investigate the relationship between surface roughness and the overall performance of the gear transmission system. This study provides a more intimate connection between the contact interface and the general behavior of the gear transmission system, enabling a better representation of real-world engineering problems. The research findings reveal that contact stiffness and damping decrease with increasing surface roughness. Higher roughness leads to greater gear vibration amplitude. Moreover, elevated surface roughness results in intensified meshing force and more significant energy loss. Surprisingly, when the roughness is appropriate, gears with rough surfaces lose less energy than those with smooth surfaces.

Comparative Performance Analysis of Gr and MoS2 Solid Lubricants During High-Temperature Dry Sliding Wear Behavior of Al2618-Based Hybrid MMCs

Comparative Performance Analysis of Gr and MoS2 Solid Lubricants During High-Temperature Dry Sliding Wear Behavior of Al2618-Based Hybrid MMCs

Thermoelastoplastic hydrodynamic lubrication contact analysis of three dimensional rough tooth surface considering micro-scale effect and thermal effect

The contact properties of gear rough surfaces during meshing are influenced by various factors. The analysis of rough surface thermoelastoplastic hydrodynamic lubrication (TPEHL) considering micro-scale effect and thermal effect has not been addressed in the literature. This study establishes a new TEPHL model with multi-factor coupling of thermal field, fluid lubrication, stress-strain, and geometric profile. Based on strain gradient theory (SG), a new thermoelastoplastic material constitutive considering micro-scale effect is developed. Subsequently, the three-dimensional rough surface TPEHL-SG analysis of gear is conducted. The paper investigates the impact of thermal and micro-scale effects on various parameters during the meshing of gear in the full oil film lubrication condition, including surface pressure, oil film thickness, surface temperature, surface deformation, and friction coefficient.

Lubrication Performance of Misaligned Journal Bearings with Flexible Structure under Shock Load Conditions

Bearings might be damaged due to shock loads caused by disturbances, in addition to static loads. In this study, a flexible structure was applied to enhance the lubrication characteristics of misaligned journal bearings subjected to impact loads. When an impact load is added to the bearing, a misaligned journal bearing has a high possibility of metal-to-metal contact. It might also lead to failure. Misalignment can occur at any time during bearing operation. A flexible structure is applied to the end of the bearing as a way to improve lubrication performance in a system where impact loads might be applied. The bearing’s lubrication performance was numerically assessed under unsteady-state conditions. An elastohydrodynamic lubrication analysis was conducted, taking into account elastic deformation. The lubrication characteristics of misaligned journal bearings were compared with the dimensionless minimum film thickness. The flexible structure and elastic modulus of the bearing were investigated so that it could support the load without contact according to the change in the maximum magnitude of the impact load. When subjected to oil film pressure, this flexible structure underwent elastic deformation, resulting in enlargement of the oil film. A misaligned journal bearing with a suitable flexible structure provided stable lubrication without metal-to-metal contact, even under shock load conditions. The flexible structure was incorporated into the high-load-bearing region of the journal bearing as a groove. Therefore, the application of a flexible structure in misaligned journal bearings can effectively enhance lubrication performance in misaligned conditions and under shock loads.

A hybrid data-driven approach for the analysis of hydrodynamic lubrication

The application of data mining technology has intensively advanced tribology research. While recent lubrication studies have highlighted the importance of data mining, researchers have not fully bridged the gap between massive lubrication data and intrinsic lubrication mechanisms. Thus, by revisiting lubrication modelling from the data-driven and physics-informed perspectives, we aim to construct a hybrid approach for hydrodynamic lubrication classification and prediction, where data-driven methods are combined with physics-informed approaches to achieve a fast and accurate prediction of the hydrodynamic lubrication scenario. Our approach will spur the application of data mining methods in lubrication studies.

Deterministic surface roughness effects on elastic material contact with shear thinning fluid media

Abstract The formation of lubrication films is described using the hydrodynamic lubrication theory, which is based on the Reynolds equation that includes shear thinning behaviors of lubricant. Contacting surfaces are considered to undergo elastic deformation owing to concentrated contact pressures that exceed 1.0 GPa in most engineering applications. Under the contact condition of a high load on a relatively small contact area, elastic deformation of contacting bodies directly influences the formation of the lubricated film. Elastohydrodynamic lubrication (EHL) analysis is applied to correctly analyze the lubricated contact. Under an EHL contact, the scale of the lubrication film thickness is frequently less than that of the surface roughness that results from either the manufacturing or running-in processes. In this work, surface roughness is considered in detail, and two-dimensional surface roughness is measured as that characterizing general engineering surface roughness. The deterministic method regarding the surface roughness is considered for computing EHL film formation under several contact conditions such as load, contact velocity, and elasticity of contacting materials.

Modified Reynolds Equation for Confined High Viscosity Film Lubrication and Lubrication Analysis of Micro-Tapered Pad Bearing

Modified Reynolds Equation for Confined High Viscosity Film Lubrication and Lubrication Analysis of Micro-Tapered Pad Bearing

Coupling analysis of timing gear dynamics and three-dimensional mixed lubrication under multi-branch shafting of marine diesel engine

Timing gears are the fundamental transmission components of marine diesel engines, and their operational reliability and efficiency are significantly impacted by their health status. The performance of timing gears is influenced by external excitations from the branch drive shaft and load input, as well as internal excitations caused by time-varying meshing stiffness and transmission errors. Therefore, it exhibits pronounced nonlinear characteristics as a result of the coupling effect between variable dynamic loading and micro-mixed lubrication induced by surface roughness and shaft vibration. The timing gear of a specific marine 20 V diesel engine is selected as the subject of investigation in this study, taking into account the impact of various types of internal and external comprehensive excitation. The three-dimensional (3D) mixed lubrication state analysis model, influenced by the coupling dynamic effect, was expanded based on the dynamic load and speed fluctuation in conjunction with the 3D line contact mixed lubrication model. The results demonstrate that the accuracy of the model can be validated through vibration testing, simulation testing, and empirical formulas for elastohydrodynamic lubrication (EHL). Additionally, the meshing process results in significant rough peak contact between the shaved surface and the ground surface, leading to potential lubrication failure. By implementing an optimization scheme that incorporates shock absorbers, the maximum contact area ratio of the four actual machining surfaces is reduced to only 16.06 %. This effectively mitigates the issue of severe rough peak contact, enhances the lubrication condition of gear pairs, and offers theoretical guidance for tribological optimization design in marine diesel engine timing gears.

Lubrication analysis of low-speed and heavy-load journal bearing in wind turbine gearbox under different operating conditions

Aiming at the working conditions of frequent starting, low speed and heavy load, and yaw tilting of radial sliding bearings in wind turbine gearboxes, a numerical analysis model of the lubrication performance coupled with instantaneous starting and operating conditions of radial sliding bearings was established based on the average Reynolds equation, and the start-up phase was analyzed. The motion trajectory of the shaft diameter and the axis center was used to obtain the change state of the bearing film thickness from the start-up to the stable stage; the influences of the comprehensive surface roughness, the journal inclination angle, and the journal rotation speed on the lubrication performance of the bearing during the whole stage of start-up and stable operation were studied respectively. The results show that the eccentricity has a maximum value in the starting stage, and the risk of film rupture caused by rough contact is the greatest. With the increase of the comprehensive surface roughness, the bearing capacity and friction coefficient both increase, and the maximum bearing capacity and friction coefficient in the starting stage are higher than those in the stable stage, which increase by about 13.62% and 131.58% respectively. With the increase of the inclination angle of the shaft diameter, the bearing capacity and friction coefficient both increase, and the maximum load capacity and friction coefficient in the starting stage are about 30% and 116% higher than those in the stable stage on average. With the increase of the speed, the bearing capacity of the bearing increases and the friction coefficient decreases, which is beneficial to improve the bearing performance. The calculation results provide an important basis for evaluating the wear risk of sliding bearings under frequent starting conditions, and provide a reference for the structural design and selection of sliding bearings, operating temperature, oil film pressure, etc.

Numerical Analysis of Oil Lubrication and Cooling of Roller Thrust Bearing in High-Performance Mixed-Flow Pump

This article deals with the numerical simulation of an oil–air multiphase flow inside the thrust bearing of a high-performance mixed-flow pump, including both the lubrication effects and the cooling of the oil by the water-cooling system based on spiral piping. The bearing is lubricated by the oil bath method with partially submersed rollers. Very complex full 3D geometry is modelled in all details, but for modelling purposes, the impacts of some model simplifications on the results are tested. The comprehensive CFD analysis is based on fully transient simulations, taking into account the different rotational speeds and different coordinate systems of all rotating components. The oil distribution on the bearing ring and roller walls as well as the oil temperature are discussed in detail. The results demonstrate that the designed cooling system is efficient in keeping the bearing and oil temperatures at safe values to guarantee bearing rating life even at extreme climatic conditions. The simulations present a comprehensive way of solving complex problems of the bearing and its cooling system applicable to engineering practice. The results of the simulations indicate also that the complexity of the computational domain and bearing clearances have a significant impact on the obtained results.

A multiphase flow study for lubrication characteristics on the internal flow pattern of ball bearing

This work proposes a general method for establishing the lubrication analysis model of ball bearing and the oil-air multiphase flow characteristics inside ball bearing is revealed by CFD. Based on the geometric feature, the micro-clearance in the chamber is introduced into the simulation model, and the complicated boundary shape of ball bearing is developed. Meanwhile, the simulation model is divided by the hexahedron elements and the mesh density near the contact region is increased, which promotes the convergence and accuracy of solution. Then, the lubrication performance experiment of ball bearing is conducted, which demonstrate that this model could capture the lubrication characteristics of ball bearing. Moreover, the evolution of hydrodynamic behavior, including the oil-air distribution, temperature and flow characteristics during different lubrication states, is displayed. The effects of structure characteristics and working condition are quantified. The results represent that the suitable clearance size could improve the internal flow patterns and hydrodynamic performance of ball bearing.

Effect of temperature rise on a tandem of ball-bearings with an O-configuration in motorized spindle under oil-air lubrication

Accurately predicting the thermal behavior of motorized spindles is a critical task in manufacturing industry. In this study, a thermo-mechanical-solid coupling-behavior on the motorized spindle in working condition was investigated and analyzed. Firstly, the bearing mechanical analysis of the motorized spindle under assembly constraints was discussed and a new coupling model was founded. Concurrently, the impacts of oil film thickness and the spacing rings on the displacement were considered into this model. Secondly, for the deformation of bearing, combined with Jones-Harris's quasi-static force–deformation bearing model, a mathematical model about a tandem of ball-bearings was built. And in this model, a new analytical method was proposed to decouple the deformation generated by thermal and centrifugal forces from the Hertz contact deformation, making the deformation analysis clear and orderly. Thirdly, from the perspective of heat generation mechanism and principle, based on the above bearing model, the elastohydrodynamic lubrication analysis on the bearing was executed, the thermal network model of bearing with multiple heat sources was set up, and the bearing node's scheme was optimized. Eventually, the effects of parameters such as speed, cooling water flow, and air flow on temperature rise and bearing parameters were calculated and analyzed, and the theoretical results were examined by tests, which provides some reference and guidance for the structural design of precision spindle.

Tribo-rheology of alcoholic and non-alcoholic beer

The analysis of mouthfeel is an important but challenging area for objective study. The use of human tasting panels presents issues of comparability between studies together with ethical limitations on consumption. Here, tribo-rheology was used in the analysis of lubrication of seven beer styles in their standard and low/no alcohol formats. Tribo-rheology was used to generate Stribeck curves showing the frictional characteristics and differences between the beers. Some possible causes for the differences in lubrication were evaluated including varying concentrations of ethanol, maltose, maltodextrin and sodium chloride. This work demonstrates statistically significant differences in lubrication between low/no alcohol beers and standard strength beers from the same producer. To conclude, the results and differences in lubrication are discussed in terms of molecular detail

Lubrication analysis of the piston ring for the two-stroke marine diesel engine based on modified radial tension

As the piston ring is inserted into the bore, it is forced against the liner by radial tension, thereby creating a seal. Radial tension not only affects the piston ring’s seal, but also significantly influences its tribological properties. To investigate the effect of non-uniform radial tension of piston ring on the lubrication properties, a contact finite element model of piston ring and cylinder liner tribo-pairs is constructed in this study. The contact pressure distribution between the tribo-pairs is determined based on this model. The obtained pressure is then regarded as the non-uniform radial tension of the ring, which is fitted to a formula. The formula is validated in two ways. Firstly, its generality is verified by simulating several different piston rings using the contact model and comparing their results with the formula. Second, a test rig was designed and set up to measure the piston ring’s circumferential tension. To verify the formula’s accuracy, an equivalent principle model of distributed pressure and concentrated force was proposed. This formula is used as an initial force to modify the piston ring mixed lubrication model. Based on this model, the lubrication performance of the piston ring with uniform radial tension and non-uniform radial tension into consideration is investigated. The findings demonstrate that the piston ring radial tension is of significance to its lubrication performance and can be modified to lessen local friction and wear issues, particularly those related to the piston ring gap, and thus improve the dependability of the piston ring.

Lubrication analysis of hydrodynamic-static hybrid bearing with deep-shallow chambers considering thermal conduction

The oil film separates the shaft-bearing system to reduce the frictional force of contact surfaces with large temperature variations owing to thermal conduction. Multiple impact factors seriously affected the lubrication behavior of the bearing during actual working process. An applicable model regarding the lubrication analysis of a hydrodynamic-static hybrid bearing with deep-shallow chambers is proposed and validated with published literature. The lubrication behavior includes film pressure, load capacity, bearing stiffness and flow rate is numerically calculated with centered finite difference method by solving the Reynolds equation. The influence of film thickness and working temperature are considered, over a range of eccentricity ratio. Moreover, the temperature variation caused by thermal conduction is analyzed in details. To investigate the influence of thermal conduction on the lubrication behavior, the results show that the load capacity, bearing stiffness, friction power, and flow power significantly decline with the consideration of thermal conduction. This study proposes an accurate model that is helpful for the design of hydrodynamic-static hybrid bearings with deep-shallow chambers under low rotational speed, heavy load, and high temperature conditions.

Influence of Cavitation and Shaft Deformation in the Analysis of Lubrication of the Stern Bearing

The cavitation phenomenon and shaft deformation have a significant impact on the tribological performance of the journal bearing. A mixed lubrication model is developed that takes into account surface roughness and asperity contact, as well as the effects of cavitation and deflection. The fluid–solid coupling effect in bearing deformation, asperity contact, and film pressure are investigated. The effect of boundary conditions on the lubrication regimes is discussed. The results of simulations with and without cavitation are compared under steady-state conditions. The results show that when cavitation is considered by the mixed lubrication model under a given load, the eccentricity is reduced, and the maximum oil film pressure is also reduced. The speed range of the bearing simulated with the mixed lubrication model increases after considering deflection deformation. The mixed lubrication model proposed in this paper is able to provide accurate results of pressure distribution and coefficient of friction and can be applied in the design and analysis of journal bearings.