Study of Rheological Properties of Industrial Lubricants (original) (raw)
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Lubrication Science, 1999
It is well k n~w n l-~ that the viscosity of crankcase lubricants decreases in the early stages of use due to shearing of the viscosity modifier N M) and, depending upon the type of service, fuel dilution. This paper examines the effects o f V M chemistry on the shearing process, and particularly how both high-temperature and low-temperature viscosities can change as a result of mechanical shear i n the Kurt Orbahn injector test and during a passenger car fleet test. Commercial olefin copolymer, styrene I butadiene, styrene I isoprene, and radial isoprene polymers were included in this study, as a way of representing the major V M chemistries used in motor oils throughout the world. The rate of change of kinematic and high-temperature, highshear-rate viscosity with time, as well as low-temperature cranking and pumping viscosity changes, were found to be characteristic of particular V M chemistries.
A Study of Variation in Viscosity-Temperature Relationship with Time of Use of Lubricant
IRJET, 2022
Lubricants are used to reduce friction and wear in machine parts with surfaces in relative motion. Viscosity is one of the most important property of the lubricant. The load bearing capacity of the lubricant depends on its viscosity. Viscosity is highly dependent on temperature hence while selecting a oil the viscosity of the oil at normal temperature, the temperature of the application and a proper viscosity temperature relationship is desired. A number of viscosity temperature relationship are available. Oil deteriorates with use time, so the viscosity of the oil also gets changed. Very few work is available to investigate the variation of viscosity temperature relationship with the time of use. It is highly desirable in deciding whether the oil has reached its limit of useful life and needs a replacement. The present work attempts to investigate the viscosity time relationship of a lubricating oil used in drill rig. Chronological samples have been collected and using one of the common available Viscosity-Temperature relationship, the variation in this relationship with time has been studied.
Lubricants, 2021
According to the ASTM D97, the pour point is the temperature below which petroleum products cease to flow. To evaluate the relevance of pour point measurements for synthetic lubricating oils, we investigated the crystallization, melting temperature and low-temperature flow behavior of one mineral and five synthetic lubricating oils. The classification of three groups emerged from this process. The formation of paraffin crystals in mineral oils (I) below the crystallization temperature causes shear-thinning behavior and a yield point. The crystallization temperature determined in the thermal analysis and rheology correlates well with the pour point. Synthetic lubricating oils, which solidify glass-like (II), exhibit a steady viscosity increase with falling temperature. The temperature at which viscosity reaches 1000 Pas corresponds well to the pour point. Synthetic oils, especially esters, with complex crystallization behavior (III), exhibit supercooling depending on the shear rate a...
International Journal on Engineering Technologies and Informatics, 2022
Looking at general technical literature, viscosity is indicated as the main commercial property of lubricating oils. The poor state of this property influences other product properties and vice versa. Lubricating oils are used between two moving or one fixed and a movable surfaces, form a protective film that has the function of minimizing contact between them and, consequently, reducing friction [1]. Its use involves constant variation of temperatures, and this variation leads to power changes in the behavior of lubricant properties. Among this group of properties, we highlight in this research thermodynamic properties of lubricating oils, such as Gibbs free energy, Enthalpy and Entropy and Activation Energy, which are quickly influenced by viscosity in scenarios of changes in lubricant use temperatures. In the case of the lubricant oil Ngol Mg-40 is produced by IMUL (Mulemba Lubricants Installation) in Luanda, which produces it with the aim of ensuring higher quality, high performance and meeting the requirements of the most reputable engine builders in the market, being the viscosity value one of the characteristics that most reveals the performance potential of this fuel. For the development of the study, we used a mixed methodology where laboratory tests were performed on samples of the Lubricant NGOL Mg-40 to verify the behavior of its viscosity (V) with the temperature variation. The results were submitted to a linear regression analysis and by the least squares method to verify the influence of viscosity behavior (V) on the thermodynamic parameters (TP) of the lubricant and we concluded that in the case in the study the viscosity positively influenced the thermodynamic properties, which makes us recommend temperature conditions of use of this lubricant for the maintenance of this quality.
Lubricants, 2018
Against the background of raw material shortage and the ever-expanding environmental consciousness, the use of biodegradable greases becomes more and more important. The aim of this experimental work is to investigate the tribological response of completely biodegradable greases. Complete biodegradable lubricating greases were formulated with high-oleic sunflower oil (HOSO) and/or castor oil, and different biodegradable thickener agents such as natural cellulose fibers of different lengths and some derivatives, as well as glyceryl and sorbitan stearates. To investigate the friction process, the model greases were tribologically examined with a nanotribometer at a normal force of 200 mN using a material combination of a steel ball on a steel disc. All frictional results, along with the volumes of wear tracks and micrographs of the main contacting area on the steel plate, are presented and discussed. In addition to this, rotational transient flow measurements were carried out on a rheometer at different temperatures to monitor the evolution of the shear stress with time at a constant shear rate, and to characterize the internal friction behavior by quantifying the energy density. All results were also analyzed from an energetic point of view.
Influence of lubricant properties on elastohydrodynamic lubrication
Wear, 1999
In hard EHL, encountered in, e.g., gears, rolling element bearings etc. the properties of the lubricant play a significant role in the forming of a lubricating film and reducing friction between the contacting surfaces. The influence of pressure and temperature on viscosity, limiting shear stress and density, has to be taken into account when creating lubricant models to be used in numerical calculations of film thickness and friction. This paper describes some experimental methods to determine these properties of a number of different lubricating oils, both from mineral, vegetable and synthetic origin. The results show that, apart from 5P4E, naphthenic mineral oil has the highest values of pressure-viscosity as well as limiting shear stress-pressure coefficients. It also exhibits the highest density increase with pressure. Rapeseed oil has a rather high pressure-viscosity coefficient but a low limiting shear stress-pressure coefficient Ž . as well as a low density increase with pressure. Thus, rapeseed oil is a strong alternative to naphthenic and also paraffinic oil since it has the ability to form a relatively thick oil film and at the same time give a low coefficient of friction. Ester, polyglycol and polyalphaolefin oils also exhibit low values of friction but are not equally good as rapeseed oil to form a lubricant film as a result of their lower pressure-viscosity coefficients. q 1999 Elsevier Science S.A. All rights reserved.
On the Steady-State Flow and Yielding Behaviour of Lubricating Greases
Fluids, 2019
Practical steady-state flow curves were obtained from different rheological tests and protocols for five lubricating greases, containing thickeners of a rather different nature, i.e., aluminum complex, lithium, lithium complex, and calcium complex soaps and polyurea. The experimental results demonstrated the difficulty to reach “real” steady-state flow conditions for these colloidal suspensions as a consequence of the strong time dependence and marked yielding behavior in a wide range of shear rates, resulting in flow instabilities such as shear banding and fracture. In order to better understand these phenomena, transient flow experiments, at constant shear rates, and creep tests, at constant shear stresses, were also carried out using controlled-strain and controlled-stress rheometers, respectively. The main objective of this work was to study the steady-state flow behaviour of lubricating greases, analyzing how the microstructural characteristics may affect the yielding flow beha...
Rheological properties of polymer-added lubricating oils
The Canadian Journal of Chemical Engineering, 1988
Rheological measurements of polyisobutylene solutions are presented. A mineral oil of low viscosity has been used as solvent. The combined effects of concentration, molecular weight and temperature were studied. It is found that the rheological data, when plotted as N, X, / ( qq s ) versus A,+ fall on a master curve over several decades of the dimensionless shear rate, irrespective of temperature, polymer concentration and molecular weight. The findings of this work can be used to address the problem of hydrodynamic lubrication of a journal bearing using a viscoelastic lubricant.
Rheological Characteristics of Corn oil used in Biodegradable Lubricant
Oriental journal of chemistry, 2023
The rheological behavior of corn oil can be studied with four rheological models found in the specialized literature.The rheological behavior of corn oil can be analyzed if it is subjected to an increasing shear rate. The behavior of this fluid can be appreciated based on the experimental data, graphically representing the variation the shearing stress with the shear velocity. This curve represents the mathematical model of the rheological behavior of the product. The rheological behavior of the corn oil was analyzed with the mixing rheometer type Viscotester VT 550 (Haake).