Lubricant Testing Research Articles

Effects of castor oil as lubricity enhancer on friction and wear characteristics of piston engine running on diesohol

Recently, ethanol has become acceptable for blending with diesel, in the so called diesohol, and is known to reduce particulate matter exhausted from diesel engines significantly. However, its poor lubricity is a concern for long-term application. Many efforts have been made to improve the lubricity of diesohol by combining additives into the ethanol-diesel blend. Castor oil is one of the most effective additives for enhancing lubricity and reducing the wear of engine components. However, the lubricating mechanism of the diesohol blended with castor oil has not been clearly reported. Therefore, in this research, the role of castor oil in lubricity enhancement was studied by varying the castor oil content in diesel from 5% to 15% v/v while retaining the ethanol content of 10% v/v. According to the ASTM D6079, the standardized lubricity test was performed using the high frequency reciprocating rig (HFRR). The fuel holder of the HFRR was modified to minimize the vaporization of the ethanol. After lubricity tests, the wear of the tested specimens was examined using a scanning electron microscope. The increase in lubricity of the blended fuel was found only up to the castor oil content of 10% v/v. At the blending amount of 10% v/v, the friction coefficient at the contact of the tested specimens decreased by 31%, while the mean wear scar diameter decreased by 25%. SEM imaging revealed delamination of the scuffed surface under diesohol lubrication without the castor oil blend. As the blending amount of the castor oil increased, the wear mode changed, and delamination was not found in the cases of the castor oil content of 10% and 15% v/v. For a long-term 220-hour engine test, diesohol blended with 10% castor oil was inferior for soot deposition and wear of metals that reduce the engine torque.

Lubricant Inerting

The recent development of nitrogen concentrators that can filter a stream of almost pure nitrogen from air now makes it practicable to operate closed lubrication systems in an inert atmosphere to limit lubricant oxidation during use—so called “lubricant inerting.” This paper outlines previous work on this topic and indicates the possible benefits of lubricant inerting using nitrogen concentrators. Two important issues are then explored: whether existing lubricant additives can work effectively in a low oxygen environment and the extent to which inerting extends lubricant life in a tribological system. It is found that friction modifiers and extreme pressure additives work as effectively or better in the absence of oxygen compared to their performance in dry air with 21% oxygen (O2). Some ashless phosphorus antiwear additives function better when no oxygen is present, some are less effective in nitrogen than in air, and some appear indifferent to the presence or absence of oxygen. High temperature lubricant testing in a tribometer indicates that degradation, as measured by viscosity increase, Fourier-transform infrared spectroscopy (FTIR), and total acid number (TAN), is almost completely suppressed in nitrogen and is greatly reduced when only 2% O2 is present. The work carried out to date suggests that lubricant inerting has the potential to provide a step-change in lubrication technology, offering greatly extended lubricant lives, enabling much higher operating temperatures, and contributing considerably to sustainability.

Friction Performance of Three-Dimension Printed PEEK for Journal Bearing Application Under Grease Lubrication

Abstract Additive manufacturing revolutionizes component and part creation, offering unmatched flexibility and reducing production time. This innovation, especially significant with semicrystalline polymers like polyetheretherketone (PEEK) at high temperatures, expands applications, including sleeves and bushes. PEEK's mechanical and tribological properties make it an attractive long-term metal replacement. However, the 3D printed PEEK surface is pivotal, and the surface structure depends on infill density, which influences its response to sliding conditions, such as speed, load, and test duration. The PEEK structure's surface patterns facilitate lubricant accommodation, particularly during boundary lubrication tests, affecting the formation of a transfer layer. Surface properties directly impact friction in 3D printed PEEK against the counterbody. Lubrication decreases friction coefficients compared to dry conditions. Wear tests show that 3D printed PEEK parts outperform extruded rod samples, displaying superior wear resistance. Surface texture and properties directly affect contact characteristics and lubricant storage. In journal bearings, varying infill percentages create surface voids, efficiently accommodating polyalphaolefin (PAO)-based grease in PEEK-based applications where oil is not preferred for sliding operations.

Influence of Adding High Flash Point, Special Jet Fuel for Brazilian Navy (QAV-5), in Brazilian Marine Gasoil (ODM), on Fuel Viscosity, Specific Gravity, Cetane Index and Lubricity

The degradation of Type 5 aviation kerosene, used in navy aircraft, (QAV-5) during the storage period was evaluated by thermal oxidation test (JFTOT) and current gum test. QAV-5 failed to meet jet fuel specifications after 16 weeks of accelerated aging, due to compromised thermal stability and substantial gum generation. Pure blends of QAV-5 and aviation kerosene and marine diesel oil (QAV-5/ODM) in proportions of 25, 50 and 75% (v/v) were analyzed according to the marine diesel oil (ODM) specification, in week zero and at intervals of four weeks throughout the aging process. Fuel viscosity, specific gravity, cetane number and lubricity decreased as the QAV-5 content in the mixture increased. The viscosity of QAV-5, however, increased with storage time. The employment of pure QAV-5 diesel engines is not advisable unless the use of aviation fuel is expressly permitted. By the fuel haze lubricity test (FLHT), QAV-5/ODM blends with up to 88% (v/v) QAV-5 content can be used in diesel engines without damaging the fuel system. However, confirmation by standard high frequency reciprocating rig (HFRR) testing would be advisable for QAV-5/ODM mixtures with QAV-5 volumetric content above 75%.

Advanced Design Validation Planning Techniques for Commercial Vehicle E-Axles

<div>Design validation plays a crucial role in the overall cost and time allocation for product development. This is especially evident in high-value manufacturing sectors like commercial vehicle electric drive systems or e-axles, where the expenses related to sample procurement, testing complexity, and diverse requirements are significant.</div> <div>Validation methodologies are continuously evolving to encompass new technologies, yet they must be rigorously evaluated to identify potential efficiencies and enhance the overall value of validation tests. Simulation tools have made substantial advancements and are now widely utilized in the development phase. The integration of simulation-based or simulation-supported validation processes can streamline testing timelines and sample quantities, all the while upholding quality standards and minimizing risks when compared to traditional methods. This study examines various scenarios where the implementation of advanced techniques has led to a reduction in the e-axle design validation plan (DVP), particularly in relation to the start of production (SOP) decision-making quality gates.</div> <div>Many DVPs incorporate tests in a specific order to enhance the validation impact of each sample and to guarantee that preconditioning tests are implemented when necessary. An instance of preconditioning is subjecting a system to thermal cycling. Thermal cycle preconditioning ensures that the sample accurately represents a real-world system when undergoing sealing-related tests, such as ingress protection testing according to ISO 20653 [<span>1</span>]. Assessing the necessary thermal cycling to “bed-in” a sample would be highly elaborate using a physical sample, but it is a straightforward aspect to extract from modern finite element analysis (FEA). A case study will be presented to evaluate the minimum required thermal cycling and determine the cost savings for the DVP.</div> <div>Furthermore, the validation supported by simulations will be showcased in the context of accelerated lifetime testing. Often, accelerating such tests necessitates a balance between the distribution of damages and the overall testing duration. By incorporating safety factors from simulations as an initial input, the distribution of damages can be adjusted to allow for some over-testing on more secure components, thereby reducing the overall testing time.</div> <div>Efficiency assessment will additionally be considered for virtual validation due to the complexity of the measurement and data acquisition, contributing to measurement uncertainty. Furthermore, simulation-based validation will be considered for the case of lubrication testing, which can be hampered by a largely qualitative assessment criteria.</div> <div>Overall, these scenarios will be evaluated for their potential to streamline the overall DVP process in terms of testing time, sample quantity, and critical path duration. This underscores the potential benefits of leveraging advanced DVP techniques for cost and time savings.</div>

Interactive Friction Modelling and Digitally Enhanced Evaluation of Lubricant Performance During Aluminium Hot Stamping

Conventional lubricant testing methods focus on lab-scale constant contact conditions, which cannot represent the scenarios in actual hot-stamping processes. In recent studies, the concept of the ‘digital characteristics (DC)’ of metal forming has been proposed by unveiling the intrinsic nature of the specific forming, which presents a timely solution to address this challenge. In this work, the transient behaviours of three dedicated lubricants during the hot stamping of AA6111 material were investigated considering the effects of various contact conditions using an advanced friction testing system, and the interactive friction modelling was established accordingly. The lubricant limit diagram (LLD) of each lubricant was then generated to quantitatively evaluate the lubricant performance following the complex tool–workpiece interactions based on the tribological DCs, and a detailed investigation on the lubricant failure regions was conducted based on the interactive friction modelling. Finally, the industrial application index (IAI) was proposed and defined as a comprehensive evaluation of lubricant applications in the industry, and the most suitable lubricant was identified among the three candidates for mass production.

Reducing Torque and Drag in Extended-Reach Wells Using Thermoplastic Polymers for Protective Sliding Rings

Extended-reach drilling represents an advanced way of drilling and accessing reservoirs that were previously economically not feasible to drain, impossible to reach or in an environmentally sensitive area. One of the main issues that appears while drilling such wells is caused by the high values of friction factor which cause high values of torque and drag. One of the suggested solutions is to use a protective sliding ring made from materials such as POM, Teflon and PA6 in combination with lubricants added to a polymer mud system. First, measurements were conducted on a lubricity tester to choose the best material and, after finishing, a mechanical wear test was conducted on a specially designed device to measure mechanical wear. Results showed that Teflon showed lower values of friction factor in comparison to steel and the mechanical wear was minimal. The lowest value of friction force was recorded for blocks made from Teflon in tested mud systems. It is also noticeable that, in polymer mud with weighting additives and lubricant, the value of the friction force is higher than in polymer mud with lubricant only.

Bottlebrush Polymers for Articular Joint Lubrication: Influence of Anchoring Group Chemistry on Lubrication Properties.

The role of carboxylic, aldehyde, or epoxide groups incorporated into bottlebrush macromolecules as anchoring blocks (or cartilage-binding blocks) is investigated by measuring their lubricating properties and cartilage-binding effectiveness. Mica modified with amine groups is used to mimic the cartilage surface, while bottlebrush polymers functionalized with carboxylic, aldehyde, or epoxide groups played the role of the lubricant interacting with the cartilage surface. We demonstrate that bottlebrushes with anchoring blocks effectively reduce the friction coefficient on modified surfaces by 75-95% compared to unmodified mica. The most efficient polymer appears to be the one with epoxide groups, which can react spontaneously with amines at room temperature. In this case, the value of the friction coefficient is the lowest and equals 0.009 ± 0.001, representing a 95% reduction compared to measurements on nonmodified mica. These results show that the presence of the functional groups within the anchoring blocks has a significant influence on interactions between the bottlebrush polymer and cartilage surface. All synthesized bottlebrush polymers are also used in the preliminary lubrication tests carried out on animal cartilage surfaces. The developed materials are very promising for future in vivo studies to be used in osteoarthritis treatment.

Effect of bionic texture on the lubrication efficiency and mechanical efficiency loss for rotating gears

In order to enhance lubrication effectiveness and transmission efficiency in gear transmission, it is imperative to minimize mechanical efficiency losses and frictional wear of the gears during the lubrication process. This paper proposes a bionic design scheme for the tooth surface structure of gears based on the surface texture of bay scallop shells, considering the operational conditions within the gearbox. Firstly, the microstructure of the bay scallop shell surface is analyzed, and a bionic gear mapping model based on the bay scallop shell surface is established. Meanwhile, the oil coverage rate and convective heat transfer coefficient of gear surfaces with different textures was analyzed using finite element analysis. The results showed that the oil coverage rate of gear tooth surfaces with bionic fringes surpassed that of conventional gear lubrication. Thirdly, based on the jet lubrication test calculation, it is proposed that the bionic gear exhibits a lower mechanical efficiency loss and wear mass compared to conventional gears, while the mechanical efficiency loss and wear mass of arc groove gear type lower than that of vertical groove gears. Finally, the optimal structure of the arc groove gear was predicted through orthogonal data analysis, and the validity of the data prediction was verified through experiments and simulations. The optimal combination of texture parameters for the arc groove gear is as follows: a texture depth of 225 μm, a texture width of 275 μm, a texture interval of 275 μm, and a texture length of 1600 μm. As a result, compared with the conventional gear, the lubrication efficiency of the optimized gear is increased by 41.98%, heat dissipation efficiency increased by 32.21%, and mechanical efficiency loss is decreased by 89.39%, the wear mass is reduced by 74.33%.

Influence of triton-assisted coconut shell derived graphene nanoplatelets in water-based drilling fluid lubricity and shale inhibition application

Influence of triton-assisted coconut shell derived graphene nanoplatelets in water-based drilling fluid lubricity and shale inhibition application

Determination of the construction material for phononic band gap structures by tribological performance

This study investigates the tribological performances of commonly used stainless steel alloys (303, 304, 316L, and 420) to determine their suitability as construction materials for periodic structures designed for inertial amplification induced phononic band gap vibration isolators. Stainless steel alloys are extensively employed in engineering structures due to their ability to withstand large stresses and exhibit excellent cyclic loading properties. In this study, stainless steel specimens are examined by dry and lubricated wear test conditions. 420 stainless steel showed highest wear resistant properties for dry and lubricated conditions. Two grades of lubricants are compared in terms of viscosities, and it is revealed that higher viscosity blocked the flow of the lubricant so that semi-dry friction occurred. Low viscosity lubricant enabled less material removal due to friction.

A Review on the Impact of Bio-Additives on Tribological Behavior of Diesel Fuels

Automobile engines require lubrication to lessen the impact of friction due to the high levels of wear and frictional heat generated by the sliding parts. Wear and friction will cause engine parts to endure for less time, be less reliable, and require more maintenance. Diesel fuel can potentially be replaced with biodiesel among other fuels. Diesel engines have a serious problem with equipment that is lubricated by the fuel itself. This study’s goal is to assess the influence of bio-additives on the diesel fuel tribological behavior and energy balance during the car’s idle running, acceleration, constant speed, and braking. Lubricity issues with reformulated diesel and lubricity test procedures are explained. The relationship between tribology and bio-additives is also briefly illustrated. According to the literature, adding bio-additives to fuel boosts its lubricity. Biodiesel has long been considered an additive with excellent lubricant properties. Even in small amounts, adding biodiesel to diesel fuel can increase its lubricity without the need for conventional lubricity additives. This is especially true for diesel fuel with ultralow sulfur. Diesel fuel characteristics determine the precise blending percentage needed to provide the proper lubricity of maximum 520 μm testing wear scars with a high-frequency reciprocating rig (HFRR), although 2% biodiesel nearly invariably imparts adequate lubricity to biodiesel blends. Tall oil fatty acid (TOFA) was one of the bio-additives investigated by HFRR. When the additive concentration was raised from 0 to 500 g/g, the wear scar diameter (WSD) of nonadditive diesel fuel was lowered by 60.3%, from 630 to 250 μm, and the coefficient of friction (COF) was lowered by 95.7%, from 0.47 to 0.02.

Friction and wear performance of polyether ether ketone (PEEK) polymers in three lubrication regimes

This experimental study investigates the friction and wear of three coatings commonly used in industrial applications, particularly in hydrodynamic bearings. The three materials under investigation were Babbitt, polyether ether ketone (PEEK) reinforced with 15% carbon fibers, and PEEK reinforced with 20% carbon fibers. The first polymer material was extruded, while the other was produced by fused deposition modelling (FDM). The materials were subjected to sliding tests in a pin-on-disc configuration, with a steel ball serving as the counter surface. The tests were conducted at room temperature, with a load of 10 N and under three different lubrication conditions: dry, grease, and oil. The linear speed was set at 0.3 m/s for the dry and semi-solid lubrication tests, while for the oil tests, the speed was set at 0.25 m/s. The greases used had consistency grades of NGLI 000 and NGLI 2. An ISO VG 68 circulation oil was used for the oil lubrication tests. Additionally, thermodynamic analyses were performed under the most severe conditions (i.e., dry) to investigate the steel-Babbitt and steel-PEEK contact.

Enhancing wear performance: A comparative study of traditional vs. additive manufacturing techniques for 17–4pH SS

Enhancing wear performance: A comparative study of traditional vs. additive manufacturing techniques for 17–4pH SS

A Methodological Approach to Assessing the Tribological Properties of Lubricants Using a Four-Ball Tribometer

Based on the analysis of standards for the testing of lubricants, both liquid and plastic, on a four-ball tribometer, and the analysis of the parameters by which lubricants are evaluated, this paper proposes a methodology and an integral parameter for the estimation of tribological properties. The methodological approach proposed in this paper allows for the integration of a variety of parameters provided in the standards for the testing of lubricants into one indicator. Herein, we show that the developed technique is based on the energy approach and takes into account the specific wear work of the test material (steel balls) in the lubricating medium to be investigated. The results of laboratory tests of a wide range of lubricants are presented: hydraulic fluids, motor and transmission oils of various purposes and classifications. It is shown that the magnitude of the integral parameter can be used to assess the effectiveness of anti-wear and anti-scuff additives in base lubricants, as well as the ranges of their applications. This allows for differentiation and quantitative evaluation of the effectiveness of such additives. The obtained results allow us to state that all tests according to the developed method are reproducible and homogeneous, which is confirmed using the Cochran criterion. The coefficient of variation during testing does not exceed 18%. We show that the presented methodology and the integral parameter can be used in the first stage of the laboratory selection tests of new lubricants and additives of various origins, reducing the costs of their development and implementation.

Experimental Study on the Influence of Stearic Acid Additive on the Elastohydrodynamic Lubrication of Mineral Oil 2137

Using an optical elastohydrodynamic lubrication (EHL) test rig, oil film thickness and the coefficient of friction (COF) were measured, and the influence of stearic acid additive on the EHL performance of mineral oil 2137 was investigated. The results showed that 2137 with 0.3 wt% stearic acid (denoted to as 2137s) achieved the same film thickness as 2137, while the COF of 2137s was significantly lower than that of 2137 when the contact was under conditions of a fully lubricant supply. Under conditions of limited lubricant supply, 2137 base oil was prone to oil starvation with the increase of entrainment velocity. On the other hand, 2137s significantly mitigated the oil starvation. This was attributed to the fact that lower surface energy by the adsorption of stearic acid results in discontinuous oil-droplet distribution on the lubrication track and, therefore, early pressure generation. Moreover, it is interesting to find that less 2137s supply quantity can produce higher film thickness when the contact is at high speeds, which is attributed to the fact that a smaller quantity of 2137s gives smaller droplets on the lubrication track, and the resultant small surface area–volume ratio presents oil more resistance to the centrifugal force and results in less oil escaping from the lubrication track. The addition of stearic acid reduced the average COF of 2137 mineral oil by about 13.3%

Deep eutectic solvent modified graphene as a lubricant for water-based drilling fluid

ABSTRACT Deep and ultra-deep drilling technology development is critical to the exploitation of ultra-deep oil and gas deposits. As the number of ultra-deep wells increases, the bottom hole temperature of certain ultra-deep wells approaches 250°C. The high-temperature and high-pressure environment can influence the stability and longevity of drilling instruments, as well as the density, rheology, and stability of drilling fluid, making wellbore stability difficult to maintain. Problems such as high torque and high friction affect the safety of downhole drilling and drilling efficiency. Adding lubricant to drilling fluid is an effective way. In this study, choline chloride (ChCl) and polyethylene glycol (PEG) were used to synthesize a deep eutectic solvent (DES), and an environmentally friendly water-based drilling fluid lubricant DES/G was prepared by compounding the DES with graphene (G). Infrared spectrum, particle size analysis, and electron microscope tests were used to characterize the structure of the lubricant. At the same time, the effect of lubricant was evaluated by extreme pressure lubricity tester and friction and wear tester, and the adhesion coefficient of filter cake was tested. At temperatures below 200°C, DES/G demonstrated a significant enhancement in the lubricating properties of drilling fluids and filter cakes. The adhesion coefficient was controlled within 0.1, and the reduction rate was exceeding 30%. With increasing dosage of the lubricant, DES/G consistently maintained a low adhesion coefficient value of 0.03803 to 0.06253 (at 180°C) and 0.0414 to 0.07337 (at 200°C). Furthermore, it exhibited higher values of reduction rate, reaching a maximum of 64%. The lubricant can increase lubricating performance by adsorbing on the metal surface to generate a strong lubricating coating and converting the sliding friction between drilling tools to rolling friction.

A structural and functional comparison between two recombinant human lubricin proteins: Recombinant human proteoglycan-4 (rhPRG4) vs ECF843

Proteoglycan 4 (PRG4, lubricin) is a mucin-like glycoprotein present on the ocular surface that has both boundary lubricating and anti-inflammatory properties. Full-length recombinant human PRG4 (rhPRG4) has been shown to be clinically effective in improving signs and symptoms of dry eye disease (DED). In vitro, rhPRG4 has been shown to reduce inflammation-induced cytokine production and NFκB activity in corneal epithelial cells, as well as to bind to and inhibit MMP-9 activity. A different form of recombinant human lubricin (ECF843), produced from the same cell line as rhPRG4 but manufactured using a different process, was recently assessed in a DED clinical trial. However, ECF843 did not significantly improve signs or symptoms of DED compared to vehicle. Initial published characterization of ECF843 showed it had a smaller hydrodynamic diameter and was less negatively charged than native PRG4. Further examination of the structural and functional properties of ECF843 and rhPRG4 could contribute to the understanding of what led to their disparate clinical efficacy. Therefore, the objective of this study was to characterize and compare rhPRG4 and ECF843 in vitro, both biophysically and functionally. Hydrodynamic diameter and charge were measured by dynamic light scattering (DLS) and zeta potential, respectively. Size and molecular weight was determined for individual species by size exclusion chromatography (SEC) with in-line DLS and multi-angle light scattering (MALS). Bond structure was measured by Raman spectroscopy, and sedimentation properties were measured by analytical ultracentrifugation (AUC). Functionally, MMP-9 inhibition was measured using a commercial MMP-9 activity kit, coefficient of friction was measured using an established boundary lubrication test at a latex-glass interface, and collagen 1-binding ability was measured by quart crystal microbalance with dissipation (QCMD). Additionally, the ability of rhPRG4 and ECF843 to inhibit urate acid crystal formation and cell adhesion was assessed. ECF843 had a significantly smaller hydrodynamic diameter and was less negatively charged than rhPRG4, as assessed by DLS and zeta potential. Size was further explored with SEC-DLS-MALS, which indicated that while rhPRG4 had 3 main peaks, corresponding to monomer, dimer, and multimer as expected, ECF843 had 2 peaks that were similar in size and molecular weight compared to rhPRG4's monomer peak and a third peak that was significantly smaller in both size and molar mass than the corresponding peak of rhPRG4. Raman spectroscopy demonstrated that ECF843 had significantly more disulfide bonds, which are functionally determinant structures, relative to the carbon-carbon backbone compared to rhPRG4, and AUC indicated that ECF843 was more compact than rhPRG4. Functionally, ECF843 was significantly less effective at inhibiting MMP-9 activity and functioning as a boundary lubricant compared to rhPRG4, as well as being slower to bind to collagen 1. Additionally, ECF843 was significantly less effective at inhibiting urate acid crystal formation and at preventing cell adhesion. Collectively, these data demonstrate ECF843 and rhPRG4 are significantly different in both structure and function. Given that a protein's structure sets the foundation for its interactions with other molecules and tissues in vivo, which ultimately determine its function, these differences most likely contributed to the disparate DED clinical trial results.

Investigation of proteinaceous algal biomass as a drilling fluid component

Investigation of proteinaceous algal biomass as a drilling fluid component

Effects of lubricant components on ash-bridge deposition characteristics in the diesel particulate filter

Effects of lubricant components on ash-bridge deposition characteristics in the diesel particulate filter