Selection Of Lubricants Research Articles

Solubility Measurements and Data Correlation of Carbon Dioxide in Pentaerythritol Tetra(2-ethylbutanoate) (PEBE6)

Carbon dioxide is one of the most promising alternative refrigerants, but its compatibility with compressor lubricants is still almost unknown. The solubility of refrigerants in oils is one of the most important properties in the selection of the proper lubricant. For this reason, in our laboratories a systematic research program on the solubility of carbon dioxide in oils has been started, putting particular attention on its dependence on lubricant chemical structure, temperature, and pressure. In this paper, experimental solubility data and their correlation of carbon dioxide in a precursor of polyol ester oil, that is, pentaerythritol tetra(2-ethylbutanoate), are presented in the temperature range of (283 to 343) K and pressures up to 10 MPa.

Development of electrostatic solid lubrication system for improvement in machining process performance

Liquid lubricants have traditionally been used to control the high heat generation in machining; however, the use of cutting fluid has become more problematic in terms of both employee health and environmental pollution. Minimization or possible elimination of cutting fluids substituting their functions by some other means is emerging as a thrust area of research in machining. Solid lubricant assisted machining is a novel concept to control the machining zone temperature without polluting the environment. The focus of this study is to explore the possibility of application of graphite as a lubricating medium in drilling of AISI 4340 steel, as a means to reduce the heat generated due to friction, towards finding an alternative to conventional coolants. To this end, an optimized solid lubricant application method, electrostatic solid lubrication experimental setup has been envisaged for effective supply of solid lubricant mixture as a high velocity jet and at an extremely low flow rate to the machining zone, thus meeting environmental requirements. The process performance is judged in terms of thrust force, tool wear, chip thickness, hole diameter and surface finish of machined workpiece keeping the other conditions constant. A comparison with the results obtained in wet and dry machining is also provided. The results obtained from the experiments show the effectiveness of the use of the solid lubricant as a viable alternative to wet and dry machining through reduction in the cutting zone temperature and favourable change in chip–tool and work–tool interaction. The proper selection and application of solid lubricant can lead to low cost, and this concept could emerge as an effective alternative to conventional coolants.

ChemInform Abstract: Selection and Application of Solid Lubricants as Friction Modifiers

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The Static and Dynamic Responses of Binary Mixture Perfluoropolyether Lubricant Films— Molecular Structural Effects

Static and dynamic properties of single-component perfluoropolyether (PFPE) lubricants have been studied for optimal lubricant selection by examining the molecular conformations that influence the thickness and the mobility for the self-healing capability in lubricant nanofilms. In this paper, we examine the physiochemical properties of the mixture of these two PFPEs using molecular dynamics (MD) simulations to find an optimal blend ratio to meet the stringent requirements for disk lubricants of ultra-low head media spacing (HMS). A coarse-grained, bead-spring model was used to model the polymer nanoblends using functional and nonfunctional PFPEs. We examined the static and dynamic responses of binary PFPE films as a function of the molecular structures including end-group functionality. The effect of the functional end-group on the static structures was examined by simulating the parallel and perpendicular components of the radius of gyration. The dynamic responses of various PFPE nanoblends were also simulated by explicitly calculating the self-diffusion coefficient of a tagged molecule. Polydispersity effect on nanoblends was also examined.

Solubility Temperature Dependence and Data Correlation of Carbon Dioxide in Pentaerythritol Tetra-2-methylbutyrate

In the past years, the employment of carbon dioxide as an alternative is becoming significant. Its compatibility with synthetic compressor lubricants is still a problem far from a solution. In the literature, only a few data on the mutual solubility of the carbon dioxide−lubricant systems are present, although it is one of the main properties affecting the selection of the proper lubricant. At our laboratories, a systematic study on the solubility of carbon dioxide in lubricants has been started, trying to identify its dependence on pressure, temperature, and oil chemical structure. In this work, experimental solubility data of carbon dioxide in pentaerythritol tetra-2-methylbutyrate, i.e., a precursor of polyol ester oil, are presented in the temperature range of (243 to 343) K and pressure up to 10 MPa. The experimental data were correlated by means of the Peng−Robinson equation of state with the Huron Vidal mixing rules in which the excess Gibbs energy at infinite pressure was represented by the UNIQUA...

The application of Fuzzy Delphi Method and Fuzzy AHP in lubricant regenerative technology selection

Due to the funding scale and complexity of lubricant regenerative technology, the selection of recycling technology and policy for waste lubricant oil can be viewed as a multiple-attribute decision process that is normally made by a review committee with experts from academia, industry, and the government. This study aims to provide a systematic approach towards the technology selection, in which two phase procedures are proposed. The first stage utilizes Fuzzy Delphi Method to obtain the critical factors of the regenerative technologies by interviewing the foregoing experts. In the second stage, Fuzzy Analytic Hierarchy Process is applied to find the importance degree of each criterion as the measurable indices of the regenerative technologies. This study considers eight kinds of regenerative technologies which have already been widely used, and establishes a ranking model that provides decision makers to assessing the prior order of regenerative technologies. The empirical study indicates that the “Proper scale” is the most important evaluation criterion considered in overall experts. The demonstration of how the prior order of regenerative technologies changes under various domains of experts is addressed as well.

Optimisation of the Stamping Processes for a Drawn-Part Made of Aluminium

The present work has been undertaken in order to investigate the possibilities of improvements in the production technology of aluminium drawn-parts. Past technology does not guarantee the production of high quality elements. Aluminium is difficult to use in sheet-metal working processes, mainly because of a susceptibility to the formation of aluminium „build-ups” on the tools, i.e. on the punch and die. The “build-ups” can be limited or even completely eliminated by a proper selection of the technological lubricants and proper surface treatment of the tools (e.g. surface coatings). In order to determine the influence of some technological lubricants and anti-adhesive layers on frictional resistance occurring during the sheet-metal forming process a typical “strip-drawing” test has been carried out. 1050A aluminium strips with thickness of 0.5mm have been drawn between two steel die inserts. Tests have been carried out with lubrication and in dry conditions. Additionally, two anti-adhesive coatings - TiN and Cr coatings were tested. Friction coefficients for different frictional pairs have been determined. In order to analyse how friction impacts on the course of sheet-metal forming process a numerical simulation based on the finite element method was performed. A four-stage stamping process of an aluminium cup was analysed. The value of the friction coefficient was changed in order to take into account frictional resistance. Thickness of the cup walls was assumed as one of the parameters determining the usefulness of the drawn-part because it determines its strength.

Binary Mixture Film of Perfluoropolyether Lubricants

It has become more and more difficult to find a single lubricant meeting all the requirements for ultra-small head-media spacing hard disk drives (HDDs). Therefore, an appropriate mixture of lubricants may be a feasible and promising alternative for future HDDs. In this paper, molecular dynamics (MD) simulations employing a bead-spring model were performed to examine the detailed structure, conformation, and dynamics of binary mixture lubricant nano films by extensively analyzing the anisotropic radius of gyration and the self-diffusion coefficient as a function of composition. Our simulation analysis indicates that a binary (or even a ternary) mixture monolayer can be a more suitable disk lubricant as compared to a single component lubricant. The conformation and mobility change by tuning the volume fraction was examined in conjunction with the optimal lubricant selection.

Seizure and wear rate testing of wheel–rail contacts under lubricated conditions using pin-on-disc methodology

An increased wear rate and a shift of wear mechanism in the wheel–rail contact has been observed in tight curves, mainly due to the change from an almost pure rolling contact to more of a sliding contact. The wheel flange–rail gauge contact is commonly known to experience the toughest conditions of the overall wheel–rail contact in terms of contact pressure and sliding velocity. The wheel flange–rail gauge contact is preferably lubricated to reduce the wear rate and to minimise the risk of transition to severe wear or seizure. The amount and type of lubrication are therefore important parameters if one is to control the wear rate. In this study, a flange contact is experimentally simulated using pin-on-disc testing, to determine the difference in wear rate among a selection of lubricants under different contact conditions. The selection of lubricants consisted of environmentally adapted oils, mineral oils, and greases containing different amounts of EP and AW additives. The results of the pin-on-disc testing indicate that both the amount and type of lubrication applied is decisive for the wear rate and active wear mechanism. Tests have also been performed to simulate either on-board or wayside lubrication, by applying the lubricant at different intervals. A general observation is that under starved lubrication conditions a transition to severe wear is initiated and the wear rate increases rapidly, i.e., all tests indicate that the contact between wheel and rail must be lubricated to avoid high wear rates.

An Experimental Investigation of Spur Gear Efficiency

In this study, a test methodology was developed for the measurement of spur gear efficiency under high-speed and variable torque conditions. A power-circulating test machine was designed to operate at speeds to 10,000rpm and transmitted power levels to 700kW. A precision torque measurement system was implemented, and its accuracy and repeatability in measuring torque loss in the power loop was demonstrated. Tests were conducted on gears with two values of modules and two surface roughness levels, operating in a dry sump jet-lubrication environment with three different gear lubricants. These tests were used to quantify the influence of these parameters on both load-dependent (mechanical), load-independent (spin), and total power loss. Trends in mechanical gear mesh efficiency and total gearbox efficiency were discussed in terms of rotational speed and transmitted torque. Finally, recommendations were made for the design of spur gear pairs, surface roughness, and lubricant selection for improved efficiency.

Molecular dynamics simulation of binary mixture lubricant films

Due to the requirements for ultra-small head-media spacing hard disk drives (HDDs), the mixture of lubricants may become feasible and promising alternative for future HDD. In this paper, molecular dynamics simulations with a bead-spring model were employed to examine the detailed structure, conformation, and dynamics of binary mixture lubricant films by analyzing the anisotropic radius of gyration and the self-diffusion coefficient as a function of volume fraction. Our simulation results indicate that the binary mixture monolayer can be more suitable as a disk lubricant in comparison with the single component. The conformation and mobility change by tuning the volume fraction was discussed in conjunction with the optimal lubricant selection.

A note on porous Rayleigh step bearings lubricated with couple-stress fluids

This paper presents the theoretical study of the effect of couple stresses on the optimum lubrication characteristics of porous Rayleigh step bearings. The lubricant with additives in the film region and also in the porous region is modelled as the Stokes couple-stress fluid. Modified Darcy type equations accounting for the polar effects in the porous region is considered and the generalized Reynolds type equation is derived for the lubrication of the porous Rayleigh step bearings. Exact solution of the generalized Reynolds type equation is obtained and the closed form expressions for the bearing characteristics are presented. Performance characteristics of the porous Rayleigh step bearing are presented for the various values of the non-dimensional parameters such as the couple-stress parameter and the permeability parameter. It is observed that the couple-stress fluid lubricants provide the increased load carrying capacity and the decreased coefficient of friction as compared to the corresponding Newtonian case. This theory suggests that, adverse effects of the presence of porous facing on the stator could be compensated with proper selection of lubricants with proper additives.

A critical evaluation of the double cup extrusion test for selection of cold forging lubricants

Abstract The performance evaluation of cold forging lubricants and coatings as well as determination of the friction coefficients is necessary for production as well as finite element (FE) simulations. The double cup extrusion test (DCET) has been widely used to evaluate cold forging lubricants, since it was believed to accurately emulate the practical conditions (severity of deformation and surface expansion) found in most cold forging applications. However, recent research and previous studies using finite element (FE) simulation as well as experiments indicated that the interface pressure conditions and surface generation in the DCET may not be comparable to those found in cold forging. Thus, the aim of this work was to evaluate the DCET by studying the influence of various geometrical and process parameters on the cup height ratio and contact pressure at the tool–workpiece interface. Based on this evaluation, recommendations are made on how to re-design the DCET and make it more sensitive to changes in interface friction.

Nanotribological characterization of perfluoroalkylphosphonate self-assembled monolayers deposited on aluminum-coated silicon substrates

Aluminum-coated silicon substrates are commonly used for various micro/nanooptoelectromechanical systems (MOEMS/NOEMS) including Digital Micromirror Devices (DMD®). For efficient and failure proof operation of these devices, ultra-thin lubricant films of self-assembled monolayers (SAMs) are increasingly being employed. Fluorinated molecules are known to exhibit low surface energy, adhesion, and friction, desirable for tribological applications. In this study, we investigate contact angle, surface energy, friction, adhesion, and wear properties of a perfluoroalkylphosphonate SAM and compare them with those of alkylphosphonate SAMs. The influence of relative humidity, temperature, and sliding velocity on the friction and adhesion behavior is studied. Failure mechanisms of SAMs are investigated by wear tests. These studies are expected to aid in the design and selection of proper lubricants for MOEMS/NOEMS.

Wear of aluminium bronze in sliding contact with lubricated stainless steel sheet material

Aluminium bronze, well known for its good sliding properties, is frequently applied as tool material in sheet metal forming (SMF) of stainless steel, e.g. for the production of washing, refrigeration and cooking equipment. The limited hardness of the material makes it, however, sensitive to tool wear that is: volumetric wear of the tool due to sliding contact with the sheet material. Conventional wear tests like the rubber wheel abrasion test or the Taber abrader test cannot be used to simulate the interaction of the tooling with lubricated sheet material. Dedicated tribo tests are therefore conducted with the slider-on-sheet test. The aim of the research is to measure the specific wear rate of aluminium bronze at SMF-like conditions. Experimental results showed a pronounced influence of lubricant selection and sheet material selection. The measured specific wear rate varied from 10 −8 mm 3 /N m for a smooth stainless steel sheet quality to 10 −6 mm 3 /N m for a rough surface quality.

Volumetric behaviour of the environmentally compatible lubricants pentaerythritol tetraheptanoate and pentaerythritol tetranonanoate at high pressures

Knowledge of proper lubricant selection and its handling can substantially influence the reliability of a refrigeration system. In this sense the awareness of several thermophysical properties of refrigerants, lubricants, and their mixtures under different conditions of pressure and temperature is highly important for designing refrigeration systems. Polyol ester oils have been proposed as lubricant candidates for refrigeration systems. In this work, we have studied the density of two polyol esters, pentaerythritol tetraheptanoate and pentaerythritol tetranonanoate, in the range 278.15 ≤ T/K ≤ 353.15 and 0.1 ≤ p/MPa ≤ 45. In addition, the behaviour of two other essential volumetric properties, namely the thermal expansion coefficient and the isothermal compressibility coefficient, as well as the internal pressure have been analysed.

EFFECT OF LUBRICANT IN MANDREL-ROTARY DRAW TUBE BENDING OF STEEL AND ALUMINUM

Mandrel-rotary draw tube bending experiments examining the effect of lubricant selection were performed using a fully instrumented Eagle EPT-75 bender. Process load and displacement data were recorded and provided significant information regarding the interaction between the various parameters affecting the bending of tubes. These data allow the direct assessment of lubrication in minimizing frictional losses during bending and the overall degree of repeatability.Experiments were performed on 76.2 mm OD, seam-welded DQAK galvanneal steel and AlMg3.5Mn aluminum alloy tubes of 1.6 and 2.0 mm nominal thickness, respectively. Tubes were bent to roughly 90 degrees after springback and the ratio of the nominal centre line bend radius to the tube outer diameter was 2.5. The aim of the study was to better understand the effect of various lubricants on the process variables, thickness and surface finish of bent steel and aluminum tubes.On a effectué des expériences de cintrage par enroulement-tension sur mandrin avec une machine à plier Eagle EPT-75 entièrement instrumentée, examinant l’effet de la sélection du lubrifiant. On a enregistré les données de charge et de déplacement de l’opération, fournissant ainsi une information importante sur l’interaction entre les divers paramètres qui affectent le cintrage des tubes. Ces données permettent une évaluation directe de l’effet de la lubrification sur la minimisation des pertes par friction lors du cintrage et permettent aussi un degré global de répétabilité.On a effectué les expériences sur des tubes soudés DQAK de 76.2 mm de diamètre extérieur en acier recuit par galvanisation et en alliage d’aluminium AlMg3.5Mn de 1.6 mm et 2.0 mm d’épaisseur nominale, respectivement. On a plié les tubes à environ 90 degrés après le retour élastique et le rapport du rayon nominal de pliure de la ligne centrale au diamètre extérieur du tube était de 2.5. Le but de cette étude était de mieux comprendre l’effet de différents lubrifiants sur les variables d’opération ainsi que sur l’épaisseur et la qualité de la surface de tubes pliés en acier et en aluminium.

Evaluation of stamping lubricants at various temperature levels using the ironing test

Lubricants are employed in stamping operations in order to (a) improve the material flow into the die cavity, (b) reduce wear and galling in the die and (c) obtain good surface finish of the part. Process conditions such as high temperatures and pressures could cause the lubricant to fail, thus resulting in galling or tearing of the part, damage to the tooling, and lost production. Therefore, selection of an appropriate lubricant based on the process conditions is important in the stamping industry. Several benchmark tests emulating stamping operations have been developed and are used to evaluate the performance of candidate lubricants. The major drawback of most of these tests is their inability to emulate high contact pressures and sliding velocities, which are crucial parameters for lubricity, especially in the case of high-speed progressive or transfer die operations involving ironing. Moreover, most of these tests are conducted at room temperature, while in reality; the process temperature can reach as high as 200 °C. The ironing tribotest developed at the Engineering Research Center for Net Shape Manufacturing (ERC/NSM) induces high contact pressures and temperatures, thus emulating the conditions in a production environment. Application of the test to screen candidate lubricants for stamping operations involving the ironing process is discussed in this paper.

Pole-Tip Protrusion Effect on High Data Rate Recording Performance

Write pole-tip protrusion (PTP) effect on the overwrite performance at high recording data rate is discussed. It is shown that the head thermal expansion during the write process may lead to the degradation of overwrite value at high recording data rate. Overwrite degradation is caused by head-disk interactions when a high-frequency pattern is written. Appropriate selection of the disk lubricant can reduce the effect of the write PTP and increase the write current setting margin. At elevated drive temperatures, excessive PTP can cause head-disk interface failure. A write timing method allowing for the recording head to cool between the write cycles is proposed. A method of head-disk interface testing and a method of mapping the head-disk interactions are further described.

Experimental investigation of porous bearings under different lubricant and lubricating conditions

The performance of porous bearing under different lubricants and lubricating conditions was experimentally investigated in this study. In order to carry out the experiments, a new test rig was designed to determine the tribological properties of based sintered bronze journal bearings that were manufactured by powder metallurgy (P/M) techniques. To determine the effects of lubricating conditions with and without oil supplement (OS) on the tribological characteristics of these bearings under static loading and periodic loadings, some experiments were carried out using different lubricants. In the tests, pure base oil (SAE 20W50), two fully formulated commercial engine oils (SAE20W50) and lubricating oils with commercial additive concentration ratio of3% were used. The worn surfaces of test bearings were examined using optical microscopy. Experimental results showed that the change in friction coefficient was more stable and in smaller magnitude under static loading than that of periodic loading. In addition, the friction coefficient and the wear rate conducted with base oil resulted in higher values than those of fully formulated oils with and without OS lubricating conditions. The experimental results obtained in this study indicated that the correct selection of lubricant and suitable running conditions were very important on the tribological characteristics of porous bearings.