Lubricants

17 pages, 4176 KiB

Open AccessArticle

Effect of Coating and Low Viscosity Oils on Piston Ring Friction under Mixed Regime of Lubrication through Analytical Modelling

by Anastasios Zavos

Lubricants 2021, 9(12), 124; https://doi.org/10.3390/lubricants9120124 - 17 Dec 2021

Cited by 9 | Viewed by 4350

Abstract

This paper presents the impact of coating topography in piston ring-liner conjunction under mixed regime of lubrication using low viscosity oils. The study provides a time efficient analytical model including mixed-hydrodynamics regime of lubrication under different contact conditions. The method modified the expressions [...] Read more.

This paper presents the impact of coating topography in piston ring-liner conjunction under mixed regime of lubrication using low viscosity oils. The study provides a time efficient analytical model including mixed-hydrodynamics regime of lubrication under different contact conditions. The method modified the expressions of the contact load and area of Greenwood-Tripp model in order to capture the real asperities interaction into contact. The model represents the tribological behavior of a thin top ring at Top Dead Centre, where boundary and mixed conditions are predominant. Electroplated CrN and PVD TiN coated rings were studied to predict the ring friction. The results are compared with an uncoated steel ring. The CrN coating shows slighter coefficient of friction, due to the coating morphology and roughness parameters. The TiN coating presents thicker lubricant films and higher coefficient of friction because the surface topography is quite rough with high peaks. This can be explained because of the major contribution of the roughness parameter and asperity slope in the boundary friction prediction. Full article

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21 pages, 9898 KiB

Open AccessArticle

A Novel Reciprocating Tribometer for Friction and Wear Measurements with High Contact Pressure and Large Area Contact Configurations

by Kim Berglund, Maria Rodiouchkina, Jens Hardell, Kalle Kalliorinne and Jens Johansson

Lubricants 2021, 9(12), 123; https://doi.org/10.3390/lubricants9120123 - 17 Dec 2021

Cited by 4 | Viewed by 4244

Abstract

There are many moving machine assemblies with conformal tribological contacts at very high contact pressures, e.g., sliding bearings, propeller shaft bearings and machine guideways. Furthermore, applications such as trunnion and guide vane bearing in Kaplan turbines have very low sliding speeds and oscillatory [...] Read more.

There are many moving machine assemblies with conformal tribological contacts at very high contact pressures, e.g., sliding bearings, propeller shaft bearings and machine guideways. Furthermore, applications such as trunnion and guide vane bearing in Kaplan turbines have very low sliding speeds and oscillatory types of motion. Although there is a vast selection of tribology test rigs available, there is still a lack of test equipment to perform friction and wear tests under high contact pressure, reciprocatory sliding and large area contact. The aim of this work is thus to develop a novel reciprocating tribometer and test method that enables friction and wear tests under low-speed reciprocatory sliding with contact pressures up to 90 MPa in a flat-on-flat contact configuration. First, a thorough description of the test rig design is given. Secondly, the influence of contact pressure and stroke length on the tribological properties of a stainless steel and polymer composite material combination is studied. The significance of considering creep, friction during the stroke and contact temperature is specifically highlighted. The novel tribometer can be used to screen different bearing and shaft material combinations and to evaluate the friction and wear performance of self-lubricating bearings for the specific operating conditions found in Kaplan turbines. Full article

(This article belongs to the Special Issue Recent Advances in Experimental Tribology: Devices and Methods)

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14 pages, 2076 KiB

Open AccessArticle

Insights into Corrosion Inhibition Behavior of a 5-Mercapto-1, 2, 4-triazole Derivative for Mild Steel in Hydrochloric Acid Solution: Experimental and DFT Studies

by Israa Abd Alkadir Aziz, Iman Adnan Annon, Makarim H. Abdulkareem, Mahdi M. Hanoon, Mohammed H. Alkaabi, Lina M. Shaker, Ahmed A. Alamiery, Wan Nor Roslam Wan Isahak and Mohd S. Takriff

Lubricants 2021, 9(12), 122; https://doi.org/10.3390/lubricants9120122 - 10 Dec 2021

Cited by 46 | Viewed by 2719

Abstract

A triazole heterocyclic compound namely 3-(4-ethyl-5-mercapto-1, 2, 4-triazol-3-yl)-1-phenylpropanone (EMTP) was examined for its corrosion protection of mild steel (MS) against 1 M hydrochloric acid medium using gravimetric techniques. EMTP exhibited excellent corrosion protection performance at low and high concentrations towards MS in HCl [...] Read more.

A triazole heterocyclic compound namely 3-(4-ethyl-5-mercapto-1, 2, 4-triazol-3-yl)-1-phenylpropanone (EMTP) was examined for its corrosion protection of mild steel (MS) against 1 M hydrochloric acid medium using gravimetric techniques. EMTP exhibited excellent corrosion protection performance at low and high concentrations towards MS in HCl solution. Comparison of corrosion protection performance of EMTP and its parent triazole and temperature effects of on inhibition efficacy were also studied. EMTP has potential corrosion inhibitor for mild steel in 1.0 M hydrochloric acid solution with the highest protection efficacy of 97% at 303 K. The weight loss findings implied that EMTP protects the metal surface corrosion through the creation of a protective layer at the surface mild steel–corrosive solution interface. The inhibitive efficacy increases with the increase of inhibitor concentration and decreases with increased temperature. The adsorption of EMTP on the surface of MS follows Langmuir’s adsorption isotherm process. DFT method was conducted on EMTP molecule to calculate the quantum chemical parameters and to determine the relationship between the molecular structure of EMTP and protection performance. The molecular parameters, such as energy gap and frontier molecular orbital (highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO)), and the absolute electronegativity (χ) value from inhibitor molecules to unoccupied d-orbital of iron atoms on the mild steel surface were also determined and correlated with protection efficiency. The theoretical findings revealed that the protection performance of EMTP increased with the increase in HOMO energy, and the nitrogen, oxygen and sulfur atoms are most probable positions for bonding through giving electrons to the d-orbital of iron atoms on the mild steel surface. Full article

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11 pages, 1440 KiB

Open AccessArticle

Theoretical Study on Compliance and Stability of Active Gas-Static Journal Bearing with Output Flow Rate Restriction and Damping Chambers

by Vladimir Kodnyanko, Andrey Kurzakov, Olga Grigorieva, Maxim Brungardt, Svetlana Belyakova, Ludmila Gogol, Alexey Surovtsev and Lilia Strok

Lubricants 2021, 9(12), 121; https://doi.org/10.3390/lubricants9120121 - 08 Dec 2021

Viewed by 1640

Abstract

The design is considered and theoretical research of operability of the active radial gas-static bearing with restrictors of output flow rate in the form of mobile rings with an elastic supports and the dampers working by Helmholtz acoustic resonator principle is done. The [...] Read more.

The design is considered and theoretical research of operability of the active radial gas-static bearing with restrictors of output flow rate in the form of mobile rings with an elastic supports and the dampers working by Helmholtz acoustic resonator principle is done. The mathematical model of the bearing dynamics and method of calculating its degree of stability are developed. The device is steady against vibrations; it has smaller power consumption compared to the known devices with input regulators, a zero and negative compliance of a gas-lubricated film. Full article

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11 pages, 612 KiB

Open AccessCommentary

Fundamentals and Advances in Elastohydrodynamics: The Role of Ramsey Gohar

by Patricia M. Johns-Rahnejat, Ghodrat Karami, Reza Aini and Homer Rahnejat

Lubricants 2021, 9(12), 120; https://doi.org/10.3390/lubricants9120120 - 08 Dec 2021

Cited by 3 | Viewed by 2616

Abstract

This paper commemorates Ramsey Gohar by acknowledging his contributions to the fields of contact mechanics and elastohydrodynamic lubrication (EHL) within the context of the developments of these subjects. A historical discourse is provided on elastohydrodynamics, from its inception in the 1940s to present. [...] Read more.

This paper commemorates Ramsey Gohar by acknowledging his contributions to the fields of contact mechanics and elastohydrodynamic lubrication (EHL) within the context of the developments of these subjects. A historical discourse is provided on elastohydrodynamics, from its inception in the 1940s to present. We demonstrate that Ramsey Gohar was not only a pioneer in the discoveries and fundamentals of the subject, but also led or contributed significantly to continual advances in the understanding of EHL and its diverse applications. Full article

(This article belongs to the Special Issue Special Issue in Elastohydrodynamics: Remembering Ramsey Gohar)

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13 pages, 7576 KiB

Open AccessArticle

Impact of Ultra-Low Viscosity Fluids on Drivetrain Functionality and Durability

by Heinrich R. Braun, Spyridon Korres, Peter Laurs and Joerg W. H. Franke

Lubricants 2021, 9(12), 119; https://doi.org/10.3390/lubricants9120119 - 08 Dec 2021

Cited by 2 | Viewed by 2303

Abstract

Increasing automotive powertrain electrification is impacting drivetrain complexity and the profiles of the fluids needed. Since the millennium, drivetrain fluid viscosities have been reduced for better efficiency, but this new challenge is driving them to unprecedented low levels. This paper assesses some of [...] Read more.

Increasing automotive powertrain electrification is impacting drivetrain complexity and the profiles of the fluids needed. Since the millennium, drivetrain fluid viscosities have been reduced for better efficiency, but this new challenge is driving them to unprecedented low levels. This paper assesses some of the potential implications of ultra-low viscosity fluids on drivetrain functionality and durability. Model formulations have been prepared from a variety of base fluids combined with additive packages. These have been evaluated in typical automotive drivetrain rig tests, as well as with some selected functional tests. In addition, the thermo-oxidative stability and electrical and thermal properties of the fluids were compared. Based on the results, the impact of low viscosity fluids on drivetrain functionality and durability varies depending on the performance parameter evaluated. For example, gear scuffing and bearing wear is highly dependent on additives, whilst gear and bearing fatigue is mainly affected by fluid viscosity. However, by carefully balancing base fluids and additives, acceptable component and fluid durability can be achieved. With respect to new electric drivetrain performance needs, the thermal properties of the finished fluid are essentially dependent on the base fluid composition, whilst its electrical properties are more influenced by additive chemistry, with some secondary impact from base fluid composition. Full article

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14 pages, 12847 KiB

Open AccessArticle

Dynamometric Investigation on Airborne Particulate Matter (PM) from Friction Materials for Automobile: Impact of Abrasive and Lubricant on PM Emission Factor

by Sung-Hun Kim, Mu Hyeok Jeong, Jaegyeom Kim, Wooyoung Shim, Sung-Uk Kwon, Jung-Ju Lee, Seung Hun Huh, Jae-Hwan Pee and Jong-Young Kim

Lubricants 2021, 9(12), 118; https://doi.org/10.3390/lubricants9120118 - 06 Dec 2021

Cited by 5 | Viewed by 2224

Abstract

Reduction of non-exhaust airborne particulate matter (PM), leading to adverse effects in respiratory system, is an urgent task. In this work, we evaluated the impact of raw materials in friction materials on PM emission due to brake wear for passenger vehicle. Time- and [...] Read more.

Reduction of non-exhaust airborne particulate matter (PM), leading to adverse effects in respiratory system, is an urgent task. In this work, we evaluated the impact of raw materials in friction materials on PM emission due to brake wear for passenger vehicle. Time- and temperature-dependent measurements using dynamometer were made for low-steel friction materials with varied abrasives and lubricant(graphite). The brake emission factor (BEF) for graphite of varied sizes ranged from 6.48 to 7.23 mg/km/vehicle. The number concentration indicates that smaller graphite (10 μm) produces more nano-sized particles than larger size (700 μm) by >50%. Depending on abrasives, BEF was found to be varied as large as by three-times, ranging from 4.37 to 14.41 mg/km/vehicle. As hardness of abrasive increases (SiC > Al₂O₃ > ZrSiO₄), higher BEF was obtained, suggesting that abrasive wear directly contributes to emissions, evidenced by surface topology. Temperature-dependent data imply that particle emission for SiC abrasive is initiated at lower speed in WLTC cycle, where disc temperature (T_disc) is ~100 °C, than that for ZrSiO₄ (T_disc >120 °C). Analysis of wear debris suggests that larger micron-sized particles include fragmented Fe lumps from disc, whereas smaller particles are, in part, formed by combination of oxidation and aggregation of nano-sized particles into small lumps. Full article

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8 pages, 890 KiB

Open AccessPerspective

The Effects of Energy Efficiency and Resource Consumption on Environmental Sustainability

by Raj Shah, Rui Chen and Mathias Woydt

Lubricants 2021, 9(12), 117; https://doi.org/10.3390/lubricants9120117 - 03 Dec 2021

Cited by 7 | Viewed by 2667

Abstract

Primary energy has become a vital part of society—from mobility, heating, and cooling to refrigeration to preserve food as well as for simple communication methods, such as texting. As such, pollution and environmental concerns regarding the impact of human activities have become mainstream [...] Read more.

Primary energy has become a vital part of society—from mobility, heating, and cooling to refrigeration to preserve food as well as for simple communication methods, such as texting. As such, pollution and environmental concerns regarding the impact of human activities have become mainstream and efforts have been made to reduce solid wastes as well as CO₂ and greenhouse gas emissions. Renewable energy is almost synonymous with environmentally friendly. While energy conversion from fossil fuels and natural gases is responsible for most of the pollution (CO₂, NO_x, SO₂, particulate matter (PM), etc.) in modern society, these processes also generated 86% of global primary energy in 2019. Furthermore, as humans become more dependent on energy, power demands will only increase with time. Material hunger represents another little perceived dependency of human prosperity. The longevity of products and goods is crucial to limit CO_2eq emissions associated with material streams. This paper will focus on two relationships: that of CO₂ and friction, and that of sustainability and wear protection. Full article

(This article belongs to the Special Issue Green Tribology: New Insights toward a Sustainable World)

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18 pages, 7952 KiB

Open AccessArticle

Study of the Kinematics and Dynamics of the Ring Pack of a Diesel Engine by Means of the Construction of CFD Model in Conjunction with Mathematical Models

by Wilman Orozco Lozano, Marlen Del Socorro Fonseca-Vigoya and Jhon Pabón-León

Lubricants 2021, 9(12), 116; https://doi.org/10.3390/lubricants9120116 - 28 Nov 2021

Cited by 6 | Viewed by 2361

Abstract

The present research aims to analyze the kinematic and dynamic behavior of the piston ring package. The development of the research was carried out through the development of numerical simulation by means of CFD. The analysis involves the three piston rings for the [...] Read more.

The present research aims to analyze the kinematic and dynamic behavior of the piston ring package. The development of the research was carried out through the development of numerical simulation by means of CFD. The analysis involves the three piston rings for the development of simulations that are closer to the real conditions of the engine since most of the investigations tend to focus on the study of the compression ring only. The simulation was reinforced by the incorporation of mathematical models, which allow determining the piston kinematics, the lubrication properties as a function of temperature, contact friction, and gas leakage. For the simulation, the CAD of the piston and the connecting rod—crankshaft mechanism was carried out, taking as a reference the geometry of a diesel engine. From the results obtained, it was possible to show that the first ring exhibits considerably greater radial and axial movement compared to the second and third piston rings. Additionally, it was shown that the first and second rings tend to maintain a negative tilt angle throughout the combustion cycle, which facilitates the advancement of the combustion gases over the piston grooves. Therefore, it is necessary to use strategies so that these rings tend to maintain a positive inclination. The analysis of the pressure conditions in the second ring are 150% and 480% higher compared to the conditions present in the third ring. Due to the above, it is necessary to focus efforts on the design of the profile of this ring. The study of energy losses showed that the combination of leakage gases and friction are responsible for a mechanical loss between 6–16%. In general, the development of the proposed methodology is a novel tool for the joint analysis of the kinematic characteristics, pressure conditions, and energy losses. In this way, integrated analysis of changes caused by piston ring designs is possible. Full article

(This article belongs to the Special Issue Advances in Tribology and LCA Applied to Thermal Machines)

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10 pages, 3334 KiB

Open AccessArticle

Three-Dimensional Finite Element Analysis of Contact Problem in Dry Friction Clutches

by Laith A. Sabri, Nadica Stojanović, Adolfo Senatore, Muhsin Jaber Jweeg, Azher M. Abed and Oday I. Abdullah

Lubricants 2021, 9(12), 115; https://doi.org/10.3390/lubricants9120115 - 27 Nov 2021

Cited by 4 | Viewed by 3966

Abstract

We present an investigation through numerical analysis (FEM) of the solution of the contact problem in friction clutch systems during engagement manoeuver. The case of high contact pressure between the sliding elements of a clutch system (flywheel, friction clutch and pressure plate) has [...] Read more.

We present an investigation through numerical analysis (FEM) of the solution of the contact problem in friction clutch systems during engagement manoeuver. The case of high contact pressure between the sliding elements of a clutch system (flywheel, friction clutch and pressure plate) has been also considered. A finite element model of a dry friction clutch system (single disc) to estimate the distributions of the contact pressure between the contact elements of the clutch system under different working conditions has been developed and the main findings are discussed. Furthermore, the effect of modules of elasticity (contact stiffness) on the distribution of contact pressure of the mating surfaces was investigated. Also, the results encompass the deformations of the contacting surfaces for different cases. This work could provide a fundamental intermediate step to obtain a partial solution to the thermos-elastic problem in order to compute the thermal-driven deformations and stresses in the automotive clutches and brakes under different working conditions. Full article

(This article belongs to the Special Issue Automotive Tribology II)

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19 pages, 8985 KiB

Open AccessArticle

Rapid Fleet Condition Analysis through Correlating Basic Vehicle Tracking Data with Engine Oil FT-IR Spectra

by András Lajos Nagy, Adam Agocs, Bettina Ronai, Péter Raffai, Jan Rohde-Brandenburger, Charlotte Besser and Nicole Dörr

Lubricants 2021, 9(12), 114; https://doi.org/10.3390/lubricants9120114 - 24 Nov 2021

Cited by 10 | Viewed by 2514

Abstract

Engine oil condition and tribological performance are strongly interrelated. Accordingly, oil condition monitoring is common in various applications. This is especially important, as oil condition depends on the fueling and utilization profile of an internal combustion engine. Common practice involves the measurement of [...] Read more.

Engine oil condition and tribological performance are strongly interrelated. Accordingly, oil condition monitoring is common in various applications. This is especially important, as oil condition depends on the fueling and utilization profile of an internal combustion engine. Common practice involves the measurement of various parameters, such as the total acid number and total base number, oxidation, nitration, viscosity, and elemental composition; thus, it can be time-consuming and resource-intensive. This study provides a methodology for rapid analysis for large vehicle fleets or sample sizes, using only Fourier-transformed infrared spectroscopy and the subsequent multivariate data analysis offers a rapid alternative to commonly available methods. The described method provides a rapid, cost-efficient, and intuitive approach to uncovering differences in the oil condition. Furthermore, understanding the underlying reasons in engine construction and the resulting chemical degradation is also possible. Full article

(This article belongs to the Special Issue Advances in Fuel-Lubricant Interactions)

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29 pages, 13569 KiB

Open AccessArticle

Experimental and Numerical Investigation of Tire Tread Wear on Block Level

by Felix Hartung, Mario Alejandro Garcia, Thomas Berger, Michael Hindemith, Matthias Wangenheim and Michael Kaliske

Lubricants 2021, 9(12), 113; https://doi.org/10.3390/lubricants9120113 - 23 Nov 2021

Cited by 5 | Viewed by 2755

Abstract

Tread wear appears as a consequence of friction, which mainly depends on surface characteristics, contact pressure, slip velocity, temperature and dissipative material properties of the tread material itself. The subsequent description introduces a wear model as a function of the frictional energy rate. [...] Read more.

Tread wear appears as a consequence of friction, which mainly depends on surface characteristics, contact pressure, slip velocity, temperature and dissipative material properties of the tread material itself. The subsequent description introduces a wear model as a function of the frictional energy rate. A post-processing as well as an adaptive re-meshing algorithm are implemented into a finite element code in order to predict wear loss in terms of mass. The geometry of block models is generated by image processing tools using photographs of the rubber samples in the laboratory. In addition, the worn block shape after the wear test is compared to simulation results. Full article

(This article belongs to the Special Issue Friction and Wear in Machine Design)

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Lubricants, Volume 9, Issue 12 (December 2021) – 12 articles

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