Viscosity Of Lubricating Oil Research Articles

Pengaruh Surfaktan Polysorbate dan Lesitin Pada Pelumas Minyak Goreng Terhadap Temperatur Mesin dan Daya

The development of the automotive world to date has grown rapidly, especially two-wheeled vehicles. Large temperature changes in lubricating oil viscosity, even if the value is too low, will reduce the lubrication of engine parts, increase friction between metals, and cause engine parts to heat up quickly. Efforts to control and overcome excessive engine heat can replace mineral-based lubricating oils with environmentally friendly and biodegradable lubricating oils. The purpose of this study is to determine the effect of using a mixture of cooking oil and surfactants C64H124O26 and C42H80NO8P as engine lubricants on the power and temperature produced by motorized vehicles. The independent variables of this research are RPM variation and mixture of pure cooking oil with lecithin and polysorbate surfactant (2.5%, 5%, 7.5%). The dependent variables are engine temperature and power. The control variables of this research are testing at room temperature, 4 stroke 125CC matic vehicle, and Raw Material using Palm cooking oil. The test method uses an infrared thermo gun for temperature and Dyno test for the highest power test on the type of Cooking Oil + Polyosrbate 7.5% with an average overall power of 5.872, then for the lowest temperature on the type of Cooking Oil + Polysorbate 2.5% with an average value of 86.2ºC.

Pengaruh Penambahan Surfaktan Estolida dan Digliserida pada Pelumas Minyak Goreng terhadap Temperatur Mesin dan Daya

Lubricating oil is a type of fluid needed by a machine to carry out work steps. Significant changes in the temperature of the lubricating oil viscosity until it is too low makes the engine components less lubricated, which causes the engine components to heat up quickly because the friction between the metals that occurs becomes greater. Lubricant that is of poor quality can cause deposits to appear in the engine room which results in the engine working harder. The aim can be achieved in this research by varying the lubricating oil with a mixture of Estolide and Diglyceride surfactant percentages of (2.5%, 5% and 7.5%). This test was carried out on a petrol motorbike with a combustion chamber volume of 125cc with standard conditions. The data that will be taken in this research includes engine temperature and power. The power testing method using a dynamometer and lubricant with cooking oil mixed with 7.5% estolide surfactant after heating produces an average value of 6.52 HP which has a higher average value than oil with a value of 5.37 HP

Shear properties and dynamic responses of greases in a micrometer-order gap

Grease is used as a lubricant in a wide range of fields, including bearings, because it reduces friction, prevents harmful wear of components, protects against rust and corrosion, and acts as a seal to prevent the invasion of dirt and water. Although most of the research on grease has focused on the environment inside the bearing, there has been little research on the fundamental lubrication mechanism of grease. It is known that thickeners, which keep a complex three-dimensional structure in the grease, have a significant effect on the shear characteristics of grease, and it is assumed that this is due to the orientation of the thickener structure in the shear direction. In this study, the apparent viscosity of grease in a micro-order gap was measured using our original viscometer and compared with the apparent viscosity measured with a submillimeter-order gap rheometer because grease may show different rheological properties compared to conventional measurements. In addition, the dynamic response of viscous resistance that appeared when each grease was subjected to a change in the shear force was quantitatively evaluated using relaxation time. As a result, the apparent viscosity remarkably decreased in a micro-order gap compared to a submillimeter gap, and two types of shear thinning mechanisms were proposed based on the orientation of the thickener: one caused by the narrow gap and the other by the shear force. In addition, the behavior of viscous resistance due to changes in the shear force depended on the type of thickener. It was also confirmed that the relaxation time of each grease correlates with its oil film-forming ability and the entanglement level of the thickener’s structure. Furthermore, the mechanism of the dynamic response was proposed based on the reorientation of thickeners.

Influence of temperature on dynamic contact characteristics of oil-jet lubricated rolling bearings

The temperature variation alters the contact state of each component during the operating process of oil-jet lubricated rolling bearings, which directly affects the dynamic performance of the bearing. However, previous studies on the dynamics of oil-jet lubricated rolling bearings do not comprehensively consider the influence of temperature factors. In addition, the impact of the temperature on the dynamic contact characteristics of the bearing is rarely investigated. To fill these gaps, this study develops a finite element model based on the mechanism of heat generation and transfer of the bearing to simulate the bearing temperature field and obtain the temperature of various components. On this basis, a dynamic model of an oil-jet lubricated axle box bearing is established to explore the influence of the radial clearance, internal temperature of the axle box and lubricating oil temperature on the contact force between the race and the rolling body by considering the influence of temperatures on the thermal deformation, lubricating oil parameters and equivalent stiffness. It was found that the influence of the temperature on bearings is primarily manifested in the elastic modulus, lubricating oil viscosity, oil film thickness, equivalent stiffness and thermal deformation. The contact force between the rolling body and the race increases significantly when the lubricating oil temperature is high, which may result in bearing pitting failure. These analysis results can provide a theoretical foundation for bearing parameter design and life research.

Film Thickness Decay and Wear Behavior of Grease-Lubricated Point Contact under Cyclic Variable Loads

For wind turbine applications, there is a cyclic load-varying process between rolling elements and raceways in pitch bearings. This kind of motion can also lead to radial fretting. However, this is seldom addressed under grease-lubricated conditions in the literature. In this study, grease-lubricated point contact problems have been investigated experimentally under cyclic load-varying conditions. The findings revealed that as the load-varying range diminishes, the variation in grease film distribution becomes more subtle and the rate of discharge of thickener fiber clusters in the stick zone decelerates. This is due to the fact that the rate of change in the Hertz contact radius is reduced and the migration of grease is weakened during the unloading process. Due to the large apparent viscosity of grease with a high soap content, entrapped grease is not easily discharged during loading, and the thickness of the film in the stick zone progressively increases as the soap content of the grease is augmented. This also causes the variable load zone to wear out more easily. As the grease is subjected to repeated loading and unloading, there is a gradual reduction in film thickness, and larger thickener fiber clusters tear, resulting in a flattened form and shear thinning. Grease containing sulphur–phosphorus additives demonstrates a superior effect on reducing fretting wear within the large variable load range but generally proves effective for smaller load-varying ranges. This study may offer insights into the degradation of grease under variable load motion and methods to prevent radial fretting wear.

Effect of varying fly ash additive ratios on viscosity variation of lubricating oil at different temperatures

This study primarily aimed to conduct experimental research, focusing on examining the effects of various fly ash additive ratios, spanning from 0% to 1%, on the alterations in lubricating oil viscosity over a temperature range extending from 25°C to 85°C. The study employed viscosity measurements using the Rhotest VR2 viscometer on a commonly used lubricating oil, and carefully analyzed their behavior with varying fly ash additive concentration ratios. The results revealed that the addition of the fly ash additive increased the oil’s viscosity at all tested temperatures. The viscosity showed a proportional increase with the amount of additive up to a 0.5% weight ratio. Beyond this concentration, the viscosity began to decrease but remained higher compared to that without the additive, attributed to the thermal conductive properties of the additive’s high-hardness metal oxide particles. The viscosity of the oil mixture with a 0.5% additive ratio increases compared to the case without the additive at temperatures of 25°C, 40°C, 65°C, 75°C and 85°C, corresponding to 13.88%, 18.32%, 37.73%, 22.91% and 32.97%, respectively. These research findings provide crucial insights for fine-tuning lubricant formulations across a spectrum of applications, especially in scenarios where temperature fluctuations play a pivotal role in lubricant efficacy. By judiciously choosing the right proportion of fly ash additive, engineers and researchers can augment the lubricative attributes of oils and enhance their resilience under diverse thermal conditions. This includes factors such as increasing viscosity, load-carrying capacity and stiffness of the oil film. The result is a machinery operation that is not only more efficient but also more dependable.

Effect of Grease Viscosity on Channeling Properties of Ball Bearings

Grease-lubricated rolling bearings transition from the churning phase to the channeling phase. This transition property affects grease life and torque properties. Therefore, the relationship between grease yield stress and grease degradation during operation, which affects this transition, has been investigated. However, there have been few studies on grease flow that affects the transition. In this study, the mechanism of grease reduction on the races was investigated for small bearings operated at low speeds, where thermal degradation and softening of the grease are less likely to occur. It was inferred that the grease transfer to the cage affects the channeling transition and that the amount of transfer varies depending on the initial grease viscosity. These findings can be applied to grease composition and cage design and are useful in providing bearings with excellent low-torque characteristics, such as in industrial motor applications.

On the Required Energy to Break Down the Thickener Structure of Lubricating Greases

The rheology of a conventional lithium-12 hydroxystearate bearing grease changes significantly when it is subjected to mechanical shear. Often this shear energy–along with the consequent entropy–is measured and used in engineering and thermodynamic models, leading to grease life models for predicting bearing seizure due to insufficiently thick film or loss of lubricity of the base oil/grease. In this degradation process, the bonds between the individual molecules, consisting mainly of the fairly weak van der Waals bonds and/or hydrogen bonds, are broken during this shearing process. In this article, we show that only a very small portion of the shear energy is needed to break these bonds and that the vast majority is dissipated as heat due to the lubricant viscosity, also known as viscous dissipation. We model the thickener as rod-shaped fibers, wherein the grease viscosity is reduced by a factor of 5 when the length of a fiber is reduced by a factor of 2.5. The energy needed to break the bonds between the molecules to shorten these fibers is 6 to 7 orders of magnitude smaller than the energy applied by shear. Hence, it is very difficult to measure this fiber structure breakage energy from grease shear aging experiments directly.

Numerical Investigation of Oil–Air Flow Inside Tapered Roller Bearings with Oil Bath Lubrication

Oil–air flow within an oil bath lubrication tapered roller bearing is essential for the lubrication and cooling of the bearing. In this paper, we develop a simulation model to investigate the flow field of tapered roller bearings with oil bath lubrication. The multiple reference frame (MRF) approach is used to describe the physical motion of the bearing, and the volume of fluid (VOF) two–phase flow model is used to track the oil–air interface in the flow field. The effects of mesh scale, geometric gap, and oil reservoir size on calculation time and convergence accuracy are examined in detail, and the effects of inner ring rotational speed and lubricant viscosity on frictional torque are systematically studied. The results of the numerical simulation indicate that as the gap distance between the raceway and the rolling elements decreases, the frictional torque is mainly generated by churning losses at the inner raceway and the rolling elements. The frictional torque increases with increasing inner ring speed and lubricating oil viscosity, with the rolling element contributing the largest portion at approximately 50% of the total. We demonstrate the effectiveness of a method to reduce frictional torque by optimizing the internal structure of the bearing to control oil flow. By optimizing the cage structure and reducing the roller half-cone angle, frictional torque can be reduced by 29.1% and 26.2%, respectively.

Study on low temperature starting strategy for high power density diesel engines

During low-temperature starting, the high viscosity and poor fluidity of diesel engine lubricating oil make it difficult to be timely replenished to the friction pair, leading to the problems of starting difficulties and wear during cold starting. To address this issue, this study completed a simulation verification work through a bench test, and carried out a transient simulation of lubricating system oil filling in the range of 1–5 s starting time and −20°C to 80°C lubricating oil temperature to obtain the transient filling characteristics of the lubrication system oil path and the friction characteristics of the bearing. The results show that extending the starting time can effectively reduce the average dry sliding speed of the bearing, thereby reducing the frictional wear of the critical friction pairs during starting; when the oil temperature is between 20°C and 30°C, the average dry sliding speed of the bearing is low and the dry sliding distance is the shortest. The research results of this study are conducive to in-depth analysis of the lubrication oil filling mechanism during cold starting, and to determine a reasonable cold starting strategy from the perspective of lubrication.

Thermohydrodynamic Lubrication Characteristics of Piston Rings in Diesel Engine Considering Transient Heat Transfer under the Parameterized Surface Texture of Cylinder Liners

The cylinder liner and piston ring form the most crucial friction pair in the diesel engine, contributing 35–40% of its overall friction losses. Recent research indicates that transient heat transfer significantly affects piston ring lubrication. However, the impact of such a transfer on varying surface textures and lubrication traits remains unclear. This paper takes the piston ring–cylinder liner of a certain diesel engine as the research object, which is based on a two-dimensional averaged Reynolds function and Greenwood–Tripp micro convex body contact model; establishes a numerical calculation model of the transient heat fluid lubrication characteristics of a vertical piston ring–cylinder liner assembly by combining the oil film thickness equation, energy equation, lubricating oil viscosity–temperature, and viscosity pressure characteristics; avoids large errors associated with assuming different temperature values for lubricants; and also uses the cylinder liner surface texturing technique to examine the effects of surface texturing on lubrication properties in the presence of transient thermal fluids. The findings indicate that employing transient thermal fluid for determining the mean value of the oil film temperature in isothermal lubrication calculations yields comparable values for minimum oil film thickness and frictional power consumption, while the friction power consumption calculated by the transient thermal fluid is slightly lower. The depth of the recesses on the surface of the cylinder liner should be minimized, while the radius of the texture should be maximized, taking into consideration the current circumstances. Compared with a cylindrical texture, a spherical texture achieves lower friction with good lubrication indexes.

Dynamic Viscosity-Temperature Characteristics and Models of Various Lubricating Oils

Background: The dynamic viscosity - temperature characteristics of lubricants are the main factors used to determine the oil film thickness and carrying capacity. There are few studies on the factors affecting the dynamic viscosity-temperature characteristics of lubricating oils and the dynamic viscosity-temperature model. Objective: This research aims to analyse the influences of lubricating oil type and initial kinematic viscosity on dynamic viscosity - temperature characteristics and present a new dynamic viscosity - temperature model. Methods: The characteristic curves of dynamic viscosity versus temperature of polyol ester oil, paraffinic mineral oil, and five types of PAO (poly a-olefin) oils with different initial viscosities were obtained by using a kinematic viscosity test device and a density test device. The influences of lubricating oil type and lubricating oil viscosity on dynamic viscosity - temperature characteristics were analysed. Based on our patent technology and repeated verification, a new dynamic viscosity - temperature model was presented. Results: Viscosity - temperature curves of three different types of lubricating oils and viscosity - temperature curves of PAO oils with different initial kinematic viscosities were obtained. A new dynamic viscosity - temperature model η=A×e^(((-T)/n) )⁡+ η_0 was proposed. Conclusion: The dynamic viscosity - temperature characteristics of lubricating oils are not only determined by the type of oils but also determined by the initial kinematic viscosity.The variation of dynamic viscosity of lubricating oils with temperature in the scope of -40~110℃ can be described by the following viscosity temperature model : , which can be used in wider temperature range than the existing models.

Sliding wear characteristics and wear constitutive equation of lead-free white metal under various lubricating liquids

In the present study, sliding wear experiments are conducted on lead-free white metal under three types of lubricating fluids, that is, two types of lubricating oils and water, and the sliding wear characteristics and friction coefficient of the sliding surface of the white metal are investigated. Lubricating fluids were selected with viscosities varying widely from 1.0 × 10−3 to 409.7 × 10−3 Pa s. Based on the experimental results, the constitutive equations of sliding wear, the coefficient of friction, and the effects of lubricating oil viscosity η and compressive stress σ are investigated. The coefficient of friction is proportional to σ0.5 and η−0.5. Therefore, as η increases in the low σ region, the coefficient of friction decreases and the amount of wear decreases. Conversely, as η decreases in the high σ region, the coefficient of friction increases; thus, the amount of wear increases and the sliding surface seizes. Furthermore, a method for quantitatively predicting the sliding wear life of white metals is devised from the perspective of machine maintenance. The wear life required to achieve a certain wear depth can be estimated using the wear constitutive equation proposed by the authors, which is expected to facilitate the safety management of bearings and the extension of their operating life.

Research on influencing factors of deformation of hydrostatic thrust bearings

When the hydrostatic thrust bearings operate under conditions of high speed and heavy load, the oil film will be strongly sheared and squeezed, which will increase the temperature of the hydrostatic oil film, resulting in uneven deformation of the workbench and tribology in serious cases. The deformation of the friction pair greatly affects the stability of the workbench during operation, and then affects the machining accuracy. Taking the hydrostatic thrust bearings as the research object, the model of hydrostatic thrust bearings was established based on the fluid–thermosolid coupling theory, and the influencing factors of the deformation of the hydrostatic thrust bearings are analyzed using ANSYS Workbench software, and the influencing laws are discussed. Finally, the correctness of the simulation method is verified by experiments. The results show that the larger the lubricating oil viscosity, the greater the deformation of the guide surface and the oil pad. With the increase in the rotation rate, the deformation of the guide surface and the oil pad increases continuously. With the increase in the inlet flow rate, the deformation of the guide surface and the oil pad is continuously reduced. In engineering practice, on the premise of ensuring the bearings capacity, low-viscosity lubricating oil should be used as much as possible, the rotation rate should be lower, or the inlet flow rate should be increased.

Study on the flash temperature phenomenon in the contact area of rolling bearings

PurposeDue to high speeds, heavy loads, large slide-to-roll ratios (SRR) and other variable operating conditions, some rolling bearings that have been working in harsh conditions may experience flash temperatures in the contact area, which may result in early damage like smearing and then affect service life. This study aims to investigate the flash temperature phenomenon of rolling bearings through theoretical and experimental analysis.Design/methodology/approachA technology for measuring temperature distribution in rolling ball on disk contact under lubrication was developed. The test-rig can simulate the ball bearing contact. The effects of working conditions such as entrainment speed, load, SRR and lubricating oil viscosity on the flash temperature were investigated.FindingsThe results of the theoretical calculation and experiments indicate that the parameters promoting the reduction of film thickness in elastohydrodynamic lubrication are always related with the number of flash points, even film thickness reduced to mixed lubrication. The flash temperature is easier to happen in conditions of high SRR, heavy load, slow entrainment speed and low viscosity oil.Originality/valueThis work conducts an experimental study on the flash temperature phenomenon, providing a test technology for bearing lubrication and failure investigation.Peer reviewThis author has opted into Transparent Peer Review available at: https://publons.com/publon/10.1108/ILT-04-2023-0104

Assessment of the relationship between lubricating oil viscosity and surface-attached adhesion rate via regression modelling

This study used a regression model, experimental data from a viscosity measurement device, and a computational technique to investigate the relationship between lubricant viscosity and surface-attached adhesion rates. Three types of used lubricants were identified and evaluated using viscosity and surface adhesion measuring instruments using three different sizes of steel balls, namely 3 mm, 3.5 mm, and 4 mm. The experimental results were then analysed using a simple linear regression model with parameter estimation. At a significance level of 0.05, the results revealed that the lubricant viscosity and the rate of surface adhesion were linearly correlated. The results of this research could be utilized by industry to control the usage of lubricating oil in industrial parts, make judgments about changing or analysing the quality of the heat-reducing lubricant at the interface between mechanical components, and so on. To maintain lubrication efficiency and increase the service life of industrial parts. As a result of fulfilling this desired goal, the regression equations generated during this study can be used to estimate surface-attached adhesion rates in other circumstances. The viscosity range utilised in this case study corresponds to the normal viscosity of the unused lubricant. The surface-attached adhesion rate can thus be accurately selected by manufacturers, and the lubrication effectiveness can also be monitored. This is another indirect waste reduction in the manufacturing chain.

Effect of grease viscosity and thickener on the wear resistance of a class D railway wheel

Using greases offers numerous advantages to the railroad system, which include the lifespan extension of wheels and rails, fuel consumption decrease, and the reduction of the friction coefficient and component wear. However, there is still a lack of understanding regarding the relationship between the grease formulation and its performance. This study aims to investigate the impact of grease viscosity and thickener on its ability to reduce wear. Thus, a series of tests were conducted using a twin disc tribometer. Four greases were tested, formulated with an identical additive package and base oil and varying viscosities (50 cSt and 500 cSt) and thickeners (calcium and lithium). The results indicated that the lithium-thickened greases performed better than the calcium ones due to lower mass losses and crack depths, smaller plastically deformed subsurface layers, and higher retentivity. Additionally, the findings revealed that the lower (50 cSt) viscosity showed superior performances also due to lower mass losses and crack depths. However, the higher viscosity exhibited higher retentivity compared to the 50 cSt greases.

Influence of Grease Properties on False Brinelling Damage of Rolling Bearings

False brinelling damage in rolling bearings can lead to reduced component lifetimes and increased noise emissions, adversely affecting machine performance. Therefore, minimizing or avoiding such damage is very important. Environmental or operating conditions that can lead to false brinelling damage often cannot be avoided. Alternatively, such damage can be significantly reduced with suitable lubricants. This study utilized a test method from the research project FVA 540 to examine the impact of the base oil viscosity and NLGI class of greases on false brinelling damage at different temperatures. The results showed a clear dependency between the base oil viscosity of greases and the extent of false brinelling damage. Two different thickeners (lithium hydroxystearate/diurea) and different base oil types (PAO/esters) were investigated for this purpose. The results indicate that temperature had a significant effect on the physical and rheological properties of greases and show the potential for reducing false brinelling damage through the selection of appropriate lubricants. These results provide valuable information to improve the performance and lifetime of rolling bearings in industrial settings.

Post-impact squeeze-out behavior of oils with different pressure-dependent rheological properties

The rapid approach of surfaces significantly increases pressure and viscosity of lubrication oil, trapping it in a dimple at the contact zone that requires time to be squeezed out. In this study, a measuring system was developed that utilized a ball-disk impact device and light interference technology to investigate the post-impact squeeze-out behavior of oils. Dimple shape evolution varied depending on the pressure-dependent rheological properties of the oils. Specifically, higher pressure–viscosity coefficients resulted in greater reduction in dimple radius, whereas lower pressure–viscosity coefficients led to quicker collapse in dimple height, providing a qualitative criterion for comparing pressure-dependent rheological properties of oils. Additionally, effect of initial dimple height and external load on the squeeze-out behavior were investigated.

Analysis on Lubrication Performance of Piston Ring-Cylinder Liner based on Numerical Simulation

This paper mainly studies the tribological performance of friction pairs and poor lubrication during piston movement. Based on the average Reynolds equation and comprehensively considering the variable viscosity and variable density characteristics of lubricating oil, a transient hydrodynamic lubrication model of the piston ring-cylinder liner friction pair is established. By solving the established lubrication model, the lubricating oil film thickness value, friction value and other parameters that can characterize the lubrication performance of the friction pair throughout the cycle are obtained, whilst revealing the surface roughness, lubricating oil viscosity and piston ring barrel surface height. And the influence mechanism of the friction performance of the friction pair is presented on the basis of the previous analysis. The research shows that improving the surface roughness of the piston ring will help to improve the lubrication, increasing the viscosity of lubricating oil will help to improve the lubricating performance of friction pairs and reduce the peak friction at the top dead centre of piston rings and improving the surface texture of the piston rings can reduce the oil film thickness and reduce the friction caused by fluid shear effect in the high-speed region.