Lubricants

15 pages, 5974 KiB

Open AccessArticle

Performance of a New Aeronautic Oil-Guiding Splash Lubrication System

by Yu Dai, Xi Chen, Duan Yang, Lanjin Xu and Xiang Zhu

Lubricants 2022, 10(6), 130; https://doi.org/10.3390/lubricants10060130 - 18 Jun 2022

Cited by 1 | Viewed by 1883

Among ever-increasing demands for low power consumption, low weight, and compact reducer systems, an oil-guiding splash lubrication method integrating the oil-guiding cylinder and pipes is suggested to be more suitable for light helicopters, instead of conventional splash or oil jet lubrication. Aiming at [...] Read more.

Among ever-increasing demands for low power consumption, low weight, and compact reducer systems, an oil-guiding splash lubrication method integrating the oil-guiding cylinder and pipes is suggested to be more suitable for light helicopters, instead of conventional splash or oil jet lubrication. Aiming at improving the lubrication and cooling performance of this special lubrication method, this paper introduces an oil-guiding channel to increase oil quantity reaching the driving gear, bearings, and spline. Firstly, the lubrication and cooling effect of the oil-guiding channel in the main gearbox is investigated at various speeds and oil depths by leveraging with a computational fluid dynamics (CFD) technique. Then, a specialized test bench is set up and utilized for experiments to verify the CFD study. These results show that the numerical results are very satisfactory with the data of experimentation, and the maximum value of relative errors is no more than 15%. What is more, the oil flow rate passing through the monitoring plane with the oil-guiding channel is much greater than that without the channel by about three orders of magnitude. It also suggests that the oil-guiding channel could dramatically increase the lubricating oil in the meshing gear pair, and significantly improve the lubrication and cooling effect. Full article

(This article belongs to the Special Issue Gear Load-Independent Power Losses)

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37 pages, 6240 KiB

Open AccessReview

The Twelve Principles of Green Tribology: Studies, Research, and Case Studies—A Brief Anthology

by Marco Freschi, Alessandro Paniz, Elena Cerqueni, Gianmarco Colella and Giovanni Dotelli

Lubricants 2022, 10(6), 129; https://doi.org/10.3390/lubricants10060129 - 17 Jun 2022

Cited by 13 | Viewed by 5043

Abstract

Sustainability has become of paramount importance, as evidenced by the increasing number of norms and regulations concerning various sectors. Due to its intrinsic trans-sectorial nature, tribology has drawn the attention of the supporters of sustainability. This discipline allows the environmental, economic, and social [...] Read more.

Sustainability has become of paramount importance, as evidenced by the increasing number of norms and regulations concerning various sectors. Due to its intrinsic trans-sectorial nature, tribology has drawn the attention of the supporters of sustainability. This discipline allows the environmental, economic, and social impacts to be decreased in a wide range of applications following the same strategies. In 2010, Nosonovsky and Bhushan drew up 12 approaches based on the 12 principles of green chemistry and the 12 principles of green engineering, defining the “12 principles of green tribology.” This review exploits the 12 principles of green tribology to fathom the developed research related to sustainability and tribology. Different approaches and innovative studies have been proposed in this short selection as references to consider for further development, pursuing the efforts of the scientific community for a sustainable future through the contribution also of tribosystems. The manuscript aims to provide practical examples of materials, lubricants, strategies, and technologies that have contributed to the overall progress of tribology, decreasing wear and friction and increasing efficiency, and at the same time promoting sustainable development, lowering toxicity, waste production, and loss of energy and resources. Full article

(This article belongs to the Special Issue Green Tribology: New Insights toward a Sustainable World 2023)

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15 pages, 4906 KiB

Open AccessArticle

Methyltrioctylammonium Octadecanoate as Lubricant Additive to Different Base Oils

by Javier Faes, Rubén González, David Blanco, Alfonso Fernández-González, Antolin Hernández-Battez, Patricia Iglesias and José Luis Viesca

Lubricants 2022, 10(6), 128; https://doi.org/10.3390/lubricants10060128 - 17 Jun 2022

Cited by 2 | Viewed by 1854

Abstract

This study investigates the use of an ionic liquid obtained from fatty acids (FAIL) as an additive at 2 wt.% in two different base oils: a mineral oil (M1) and a polyol ester (E1). Physicochemical characterization of the base oil–FAIL blends confirmed the [...] Read more.

This study investigates the use of an ionic liquid obtained from fatty acids (FAIL) as an additive at 2 wt.% in two different base oils: a mineral oil (M1) and a polyol ester (E1). Physicochemical characterization of the base oil–FAIL blends confirmed the miscibility of the FAIL in the base oils. The addition of the FAIL hardly changed the density of the base oils and the viscosity slightly increased at lower temperatures. The tribological performance of the base oils and their blends with the FAIL was determined using three different tests: Stribeck curve determination and tribofilm formation tests, both under sliding/rolling motion, and reciprocating wear tests. The M1 + FAIL blend showed the lowest friction values under the mixed lubrication regime due to its higher viscosity, while the E1 + FAIL showed the lowest friction values under the elastohydrodynamic lubrication regime, which may well have been due to its higher polarity. Only the E1 + FAIL blend outperformed the antiwear behavior of the base oil, probably because it has better chemical affinity (higher polarity) for the metallic surface. SEM images showed that the predominant wear mechanism was adhesive-type with plastic deformation and XPS studies proved that the presence of increasing amounts of organic oxygen on the wear scar caused better antiwear performance when the E1 + FAIL blend was used. Full article

(This article belongs to the Special Issue New Developments and Future Trends of Ionic Liquids as Lubricants)

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20 pages, 10241 KiB

Open AccessArticle

Unbalance Response Analysis of a Spindle Supported on Gas Bearings: A Comparison between Different Approaches

by Federico Colombo, Luigi Lentini, Terenziano Raparelli, Andrea Trivella and Vladimir Viktorov

Lubricants 2022, 10(6), 127; https://doi.org/10.3390/lubricants10060127 - 17 Jun 2022

Viewed by 1440

Abstract

Gas journal bearings are widely employed in high-speed spindles for the micromachining industry. Compared to their oil and rolling counterparts, gas bearings have a longer life span, lower friction and a lower level of noise. In order to design accurate high-speed spindles supported [...] Read more.

Gas journal bearings are widely employed in high-speed spindles for the micromachining industry. Compared to their oil and rolling counterparts, gas bearings have a longer life span, lower friction and a lower level of noise. In order to design accurate high-speed spindles supported by externally pressurized gas bearings, it is vital to analyze the characteristics of rotor bearing systems. In this paper, we present an analysis of the unbalance response of a high-speed spindle supported by gas journal bearings. A number of aspects to enhance the accuracy of the system are discussed. We performed the analysis by considering a nonlinear and a linearized numerical model validated through experimental measurements. Full article

(This article belongs to the Special Issue Tribology in Manufacturing and Design)

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15 pages, 4491 KiB

Open AccessArticle

Assessment of Stability and Thermophysical Properties of Jojoba Nanofluid as a Metal-Cutting Fluid: Experimental and Modelling Investigation

by Gaurav Gaurav, Govind Sharan Dangayach, Makkhan Lal Meena and Abhay Sharma

Lubricants 2022, 10(6), 126; https://doi.org/10.3390/lubricants10060126 - 16 Jun 2022

Cited by 3 | Viewed by 1933

Abstract

Nanofluids based on vegetable oil have emerged as ecological alternatives to conventional cutting fluids. Jojoba-seed oil has recently been identified as adequate for use in metal cutting. Aiming to assess the stability and thermophysical properties of jojoba nanofluids, this article reports an experiment- [...] Read more.

Nanofluids based on vegetable oil have emerged as ecological alternatives to conventional cutting fluids. Jojoba-seed oil has recently been identified as adequate for use in metal cutting. Aiming to assess the stability and thermophysical properties of jojoba nanofluids, this article reports an experiment- and modelling-based investigation. The stability, viscosity and thermal conductivity of jojoba MoS₂ nanofluid were studied across a broad range of temperatures and concentrations of nanoparticles. The functional relationship of the viscosity and thermal conductivity to the temperature and concentration was determined by regression analysis. In addition to confirming known phenomena, vis-à-vis the effect of the concentration and temperature on the viscosity and thermal conductivity, this study shows that the increase in the thermal conductivity in line with the concentration stagnates after an initial sharp rise due to an increase in the attractive forces between the particles. The viscosity displays a second-order interactive relationship with the temperature and concentration of the nanoparticles, whereas thermal conductivity follows a complex third-order interaction model. In addition to being economical, jojoba nanofluid matches or surpasses the nanofluid prepared using commercially available mineral-oil-based cutting fluid (LRT 30)—which is specially designed for the minimum-quantity lubrication method of metal cutting. Conclusively, this investigation paves the way for the shop-floor application of jojoba nanofluid in metal-cutting operations. Full article

(This article belongs to the Special Issue Numerical Simulations in Lubrication)

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13 pages, 6918 KiB

Open AccessArticle

Friction and Wear Properties of a Nanoscale Ionic Liquid-like GO@SiO₂ Hybrid as a Water-Based Lubricant Additive

by Liang Hao, Wendi Hao, Peipei Li, Guangming Liu, Huaying Li, Abdulrahman Aljabri and Zhongliang Xie

Lubricants 2022, 10(6), 125; https://doi.org/10.3390/lubricants10060125 - 13 Jun 2022

Cited by 7 | Viewed by 2191

Abstract

In this study, a nanoscale ionic liquid (NIL) GO@SiO₂ hybrid was synthesized by attaching silica nanoparticles onto graphene oxide (GO). It was then functionalized to exhibit liquid-like behavior in the absence of solvents. The physical and chemical properties of the synthesized samples [...] Read more.

In this study, a nanoscale ionic liquid (NIL) GO@SiO₂ hybrid was synthesized by attaching silica nanoparticles onto graphene oxide (GO). It was then functionalized to exhibit liquid-like behavior in the absence of solvents. The physical and chemical properties of the synthesized samples were characterized by means of a transmission electron microscope, X-ray diffraction, Fourier transform infra-red, Raman spectroscopy, and thermogravimetric analysis. The tribological properties of the NIL GO@SiO₂ hybrid as a water-based (WB) lubricant additive were investigated on a ball-on-disk tribometer. The results illustrate that the NIL GO@SiO₂ hybrid demonstrates good dispersity as a WB lubricant, and can decrease both the coefficient of friction (COF) and wear loss. Full article

(This article belongs to the Special Issue Advances in Water-Based Nanolubricants)

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19 pages, 6491 KiB

Open AccessArticle

Towards a Standard Approach for the Twin Disc Testing of Top-Of Rail Friction Management Products

by Ben White, Zing Siang Lee and Roger Lewis

Lubricants 2022, 10(6), 124; https://doi.org/10.3390/lubricants10060124 - 13 Jun 2022

Cited by 9 | Viewed by 2193

Abstract

A wheel/rail friction coefficient that is too low can result in damage to the wheel and rail due to slips and slides, delays and safety concerns. A friction coefficient that is too high can result in excessive wear, noise and rolling contact fatigue. [...] Read more.

A wheel/rail friction coefficient that is too low can result in damage to the wheel and rail due to slips and slides, delays and safety concerns. A friction coefficient that is too high can result in excessive wear, noise and rolling contact fatigue. Changing contact and environmental conditions cause variations in wheel/rail friction, so friction management products, applied via wayside or on-board applicators, are used to either increase or decrease the friction coefficient so that an improved level is reached. They can be split into three classes; traction enhancers, lubricants and top-of-rail products (including water-based, oil/grease-based and hybrid products). This paper focuses on top-of-rail products and describes the different apparatus, contact conditions, product application methods and result interpretation that have been used to test these products and highlights the requirement for a more standardised test method. A proposed test method is outlined, which uses a twin disc test rig to collect “effective level of friction” and “retentivity” data to assess product effectiveness. More comparable and standardised data will ensure that maximum benefit is obtained from each set of results and help both product development and the approvals process. Full article

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14 pages, 4762 KiB

Open AccessArticle

Study on Factors Influencing Film Formation of Grease and Calculation Model for Grease Film Thickness

by Zhe Zhang, Yanshuang Wang, Jianghai Lin and Dongfeng Wang

Lubricants 2022, 10(6), 123; https://doi.org/10.3390/lubricants10060123 - 12 Jun 2022

Cited by 5 | Viewed by 1902

Abstract

The grease film thickness was measured in fully flooded elastohydrodynamic lubrication, and the influence of rolling speed, load, consistency, base oil type and thickener type on grease film thickness was analyzed. A new calculation model for grease film thickness was established. The results [...] Read more.

The grease film thickness was measured in fully flooded elastohydrodynamic lubrication, and the influence of rolling speed, load, consistency, base oil type and thickener type on grease film thickness was analyzed. A new calculation model for grease film thickness was established. The results show that the grease film thickness increases with the increasing rolling speed, and then levels off with the amount of thickener in the contact region reaching an equilibrium. The degree of grease film enhancement comparing to its base oil will depend on thickener type and consistency. The larger the atmospheric viscosity and pressure-viscosity coefficient of the base oil, the higher the film thickness of the greases with the same thickener. The grease film thicknesses with the same base oil and different thickeners are determined by the size of thickener particles at the same consistency or concentration. The larger the consistence of the grease, the larger the effective viscosity of the grease at the contact and the thicker the grease film thickness whose base oil has the same type and viscosity along with the same type of thickener. The calculated values by the new model are in good agreement with the measured values. Full article

(This article belongs to the Special Issue Recent Advances in Lubricating Greases II)

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8 pages, 3395 KiB

Open AccessArticle

Thermal Error Analysis of Five-Axis Machine Tools Based on Five-Point Test Method

by Yu Li, Hongchuan Tian, Difei Liu and Quanbo Lu

Lubricants 2022, 10(6), 122; https://doi.org/10.3390/lubricants10060122 - 10 Jun 2022

Cited by 4 | Viewed by 1747

Abstract

The accuracy of five-axis machine tools is a key performance indicator. Among the various error sources of high precision five-axis machine tools, thermal and geometric errors occupy the majority. Thermal errors have become the largest error source of high precision five-axis machine tools, [...] Read more.

The accuracy of five-axis machine tools is a key performance indicator. Among the various error sources of high precision five-axis machine tools, thermal and geometric errors occupy the majority. Thermal errors have become the largest error source of high precision five-axis machine tools, accounting for about 45% of the total errors. Accurate measurement of thermal errors plays a vital role in improving the accuracy of five-axis machine tools. Taking the Shenyang HTM50100 turning and milling machine tool as an example, this paper proposes a method to measure the thermal error of the machine tool spindle using the five-point test method. In the process of thermal error modeling, we select the temperature key point and analyze the collected data. Finally, we evaluate thermal error model. The method is verified by an experiment. The experiment results show that the method is highly accurate, fast, and easy to use. It provides a theoretical basis and practical method for the measurement of thermal errors on five-axis machine tools. By evaluating the method based on multiple linear regression, the predictive ability of the model is about 77%. Compared with LSTM, the prediction accuracy is improved by 5.08%. Full article

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12 pages, 1662 KiB

Open AccessArticle

A General Approach to Determine the Constitutive Parameter Dependence of Global Quantities at Sharp Contact Testing of Rigid-Plastic Materials

by Per-Lennart Larsson

Lubricants 2022, 10(6), 121; https://doi.org/10.3390/lubricants10060121 - 09 Jun 2022

Cited by 1 | Viewed by 1598

Abstract

Correlation of sharp contact problems is investigated with the focus on rigid-plastic contact behavior pertinent to engineering metals and alloys. The aim is to determine relations between the contact hardness and constitutive parameters suitable for material characterization. This is performed by using a [...] Read more.

Correlation of sharp contact problems is investigated with the focus on rigid-plastic contact behavior pertinent to engineering metals and alloys. The aim is to determine relations between the contact hardness and constitutive parameters suitable for material characterization. This is performed by using a solution approach where the transition zone between elastoplastic and rigid-plastic contact behavior is analyzed, especially as regards the size of the plastic zone. This approach is applied to three different cases: (1) sharp indentation of von Mises plastic materials; (2) sharp indentation of Drucker–Prager plastic materials; (3) sharp scratching of von Mises plastic materials. Established finite element simulations are used in order to verify the analysis of these three cases. In addition, based on the suggested approach, new results concerning the constitutive parameter dependence of the relative contact area, pertinent to case (2) above, are presented and compared with finite element simulations. All of the results are valid for metals and alloys but also for elastic–plastic crystalline materials where the contact deformation regime is close to the rigid-plastic one. Full article

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16 pages, 12991 KiB

Open AccessArticle

Tribological Behavior and Wear Mechanism of Ni-Nano TiO₂ Composite Sintered Material at Room Temperature and 600 °C

by Adam Piasecki, Mateusz Kotkowiak, Maciej Tulinski and Adam Kubiak

Lubricants 2022, 10(6), 120; https://doi.org/10.3390/lubricants10060120 - 08 Jun 2022

Cited by 2 | Viewed by 1733

Abstract

In the present work, Ni-10 wt.%TiO₂ self-lubricating composite sinters were prepared via a powder metallurgy. Commercially available powder of nickel and non-commercial nanometric titanium dioxide (approx. 30 nm size) produced by the microwave method was used. The produced sinters were characterized by [...] Read more.

In the present work, Ni-10 wt.%TiO₂ self-lubricating composite sinters were prepared via a powder metallurgy. Commercially available powder of nickel and non-commercial nanometric titanium dioxide (approx. 30 nm size) produced by the microwave method was used. The produced sinters were characterized by evenly distributed TiO₂ particles in a nickel matrix and a hardness of approx. 110 HV5. Pin-on-disc wear tests at room temperature and 600 °C were carried out. Light Microscopy (LM), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and X-Ray Diffraction (XRD) were used to characterize the wear mechanism of sintered materials. The coefficient of friction of the Ni-10 wt.% TiO₂—Inconel^®625 friction pair tested at room temperature was approx. 0.52. At the test temperature of 600 °C, the same friction pair had a friction coefficient of 0.35. The main wear mechanisms in dry friction conditions at 23 °C were cutting and ploughing. At the test temperature of 600 °C, formation of tribofilm on the surfaces of the friction pair was observed, which reduces the wear by friction. Full article

(This article belongs to the Special Issue Multiscale Tribology of Solid Lubricants)

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10 pages, 5414 KiB

Open AccessArticle

Development of a Cryogenic Tester with Air Bearing to Test Sliding-Rolling Contact Friction

by Fengbo Liu, Bing Su, Guangtao Zhang, Jiongli Ren and Wenhu Zhang

Lubricants 2022, 10(6), 119; https://doi.org/10.3390/lubricants10060119 - 07 Jun 2022

Cited by 7 | Viewed by 1913

Abstract

This study aimed to test the friction coefficient of cryogenic bearing lubrication materials. A ball-on-disc type friction tester was developed in our lab using air bearings that could simulate the movement of cryogenic bearings under sliding-rolling contact. The tester is equipped with a [...] Read more.

This study aimed to test the friction coefficient of cryogenic bearing lubrication materials. A ball-on-disc type friction tester was developed in our lab using air bearings that could simulate the movement of cryogenic bearings under sliding-rolling contact. The tester is equipped with a temperature-controlled chamber to provide a minimum −175 °C low-temperature environment. Using air bearings is an important technique to reduce the base friction of the tester measurement system and ensure the accuracy of the friction coefficient measurement. The friction coefficients of the Ag coating and the PTFE coating were measured at different sliding-rolling velocities on this tester, and the results showed that the friction coefficient curves agreed well with the Gupta sliding model. The developed tester will provide important data for the dynamic analysis and life evaluation of the cryogenic bearings. Full article

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20 pages, 7822 KiB

Open AccessArticle

ZDDP Tribofilm Formation from a Formulated Oil on Textured Cylinder Liners

by Leonardo C. Dias, Giuseppe Pintaude, Alessandro A. O. F. Vittorino and Henara L. Costa

Lubricants 2022, 10(6), 118; https://doi.org/10.3390/lubricants10060118 - 07 Jun 2022

Cited by 6 | Viewed by 2484

Abstract

Surface texturing can improve lubrication and entrap wear debris but increases the effective roughness of the surfaces, which can induce higher contact pressures. On the one hand, this can be detrimental, but on the other hand, the increase in contact pressure could be [...] Read more.

Surface texturing can improve lubrication and entrap wear debris but increases the effective roughness of the surfaces, which can induce higher contact pressures. On the one hand, this can be detrimental, but on the other hand, the increase in contact pressure could be used to activate the formation of a ZDDP tribofilm from fully-formulated lubricants. This work investigates the synergistic effect between surface texturing via Maskless Electrochemical Texturing (MECT) and ZDDP additive. The surface texture consisted of an array of annular pockets manufactured on a gray cast iron cylinder liner. These textured surfaces were evaluated by scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDX). The results indicated that surface texturing via MECT changes the chemical composition of the surfaces, by inducing a preferential dissolution of the metal matrix. Consequently, it exposed the carbon present in the material. The tribological performance was evaluated by a ring-on-cylinder-liner tribometer in reciprocating sliding under boundary lubrication conditions using both a base oil and a commercial formulated oil containing ZDDP additive. For comparison, a commercially honed liner was also tested. After the tribological tests, the surfaces were evaluated by white light interferometry and SEM/EDX. Although the textured surfaces showed higher friction, they induced more ZDDP-tribofilm formation than conventional cylinder liner finish. Full article

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

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9 pages, 2516 KiB

Open AccessArticle

Tribological Characteristics of Nano-Lubricated High-Speed Rolling Bearings Considering Interaction between Nanoparticles and Rough Surface

by Xiaojie Tang and Junning Li

Lubricants 2022, 10(6), 117; https://doi.org/10.3390/lubricants10060117 - 06 Jun 2022

Cited by 5 | Viewed by 1744

Abstract

The embedding situation between various nanoparticles and rough surfaces affects the lubrication characteristics of rolling bearings. If not properly handled, this can easily lead to wear damage of rolling bearings. Therefore, the friction and wear mechanism of nano-lubricated high-speed rolling bearings under various [...] Read more.

The embedding situation between various nanoparticles and rough surfaces affects the lubrication characteristics of rolling bearings. If not properly handled, this can easily lead to wear damage of rolling bearings. Therefore, the friction and wear mechanism of nano-lubricated high-speed rolling bearings under various nanoparticle embedded states is studied in this manuscript. Mixed oils containing different sized SiO₂ nanoparticles and dispersants are prepared, and then the tribology test of nano-lubricated high-speed rolling bearings considering the interaction between various nanoparticles and the rough surfaces is conducted. The friction and wear properties such as coefficient of friction, wear volume and real-time temperature rise of high-speed rolling bearings under different embedding conditions are revealed, and the anti-wear mechanism of the nano-lubricated high-speed rolling bearings is obtained. The results show that compared to the complete non-embedded state, the complete embedded state of different nanoparticles effectively improves the anti-wear effect of the bearing. When the nanoparticle mixed oil is added, the bearing still has good anti-wear performance under the conditions of high speed and lack of oil. As for the light loaded rolling bearing adopted with nano-mixed oil, the coefficient of friction is appropriately increased, as well as the skid reduced, while the wear of the rolling bearing is effectively reduced. This research will provide theoretical basis and important reference for nano-lubrication and its application in aviation rolling bearings. Full article

(This article belongs to the Special Issue Friction and Lubrication of Sliding Bearings, Volume II)

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16 pages, 10532 KiB

Open AccessArticle

Research on the Mechanism of the Stiffness Performance of Rolling Bearings under Wrong Assembly State

by Yanfei Zhang, Yunhao Li, Lingfei Kong, Zhenchao Yang and Yue Si

Lubricants 2022, 10(6), 116; https://doi.org/10.3390/lubricants10060116 - 05 Jun 2022

Cited by 1 | Viewed by 2188

Abstract

In this paper, a quasi-static angular contact ball bearing model, considering assembly accuracy is constructed, while a numerical solution method for bearing stiffness under bad assembly state is established. A 7014C angular contact ball bearing is used as the research object and five [...] Read more.

In this paper, a quasi-static angular contact ball bearing model, considering assembly accuracy is constructed, while a numerical solution method for bearing stiffness under bad assembly state is established. A 7014C angular contact ball bearing is used as the research object and five groups of different spacer inclinations are designed to imitate the installation error of the spindle bearing. The bearing stiffness performance was comparatively analyzed, according to the five spacers. The effect of preload and rotation speed on bearing stiffness are systematically investigated, considering different parallelism errors, as induced by the spacers. The influence mechanism of the badly assembled bearing on the respective stiffness anisotropy is studied based on the proposed model. The results show that the variations of the inclination between the inner and outer rings of the bearing exhibit a very weak effect on the axial stiffness, while the influence on the radial and angular stiffness is more significant. Full article

(This article belongs to the Special Issue Advances in Bearing Lubrication and Thermal Sciences)

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18 pages, 5687 KiB

Open AccessArticle

Research on Contact and Wear Characteristics of the Planetary Roller Screw Mechanism with Screw Misalignments

by Junjie Meng, Xing Du, Xin Zhao, Junwei Zheng, Dingwei Wang and Long Wan

Lubricants 2022, 10(6), 115; https://doi.org/10.3390/lubricants10060115 - 03 Jun 2022

Cited by 6 | Viewed by 1932

Abstract

Misalignments are unavoidable in most applications of the planetary roller screw mechanism (PRSM) due to many potential causes. However, the effect of screw misalignments on the contact characteristics for the PRSM have not been thoroughly investigated. In this paper, a comprehensive analytical procedure [...] Read more.

Misalignments are unavoidable in most applications of the planetary roller screw mechanism (PRSM) due to many potential causes. However, the effect of screw misalignments on the contact characteristics for the PRSM have not been thoroughly investigated. In this paper, a comprehensive analytical procedure for the PRSM performance considering screw misalignments is proposed. First, the contact positions and clearances of the PRSM with screw misalignments are calculated. Next, an improved model is presented for evaluation of the load distribution, in which the variation of axial clearances is taken into consideration. The numerical results are validated by finite element analysis. Then, the precision loss model caused by wear is derived considering the variation of contact forces. The results indicate that the contact positions slightly change due to the misalignment angle of the screw, while the axial clearances and load distribution at the screw-roller interface are significantly affected. At the same time, the contact forces over thread vary periodically. In addition, the screw misalignment aggravates the wear of the PRSM, resulting in accuracy degradation. The theoretical investigations lay the foundation for the engineering application of the PRSM. Full article

(This article belongs to the Special Issue Advances in Wear Predictive Models)

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12 pages, 3281 KiB

Open AccessArticle

Evolution of the Geometric Structure of X39Cr13 Steel upon Thermochemical Treatment Specific to Medical-Grade Steels

by Monika Gwoździk, Mirosław Bramowicz and Sławomir Kulesza

Lubricants 2022, 10(6), 114; https://doi.org/10.3390/lubricants10060114 - 03 Jun 2022

Cited by 1 | Viewed by 1399

Abstract

This paper presents the results of the multi-aspect surface characterization of X39Cr13 steel samples subjected to technological processes specific to medical instrumentation, such as heat and thermochemical treatment, as well as sterilization, which are implemented in corrosion resistance measurements. The application of numerical [...] Read more.

This paper presents the results of the multi-aspect surface characterization of X39Cr13 steel samples subjected to technological processes specific to medical instrumentation, such as heat and thermochemical treatment, as well as sterilization, which are implemented in corrosion resistance measurements. The application of numerical methods of fractal analysis to averaged profiles obtained from SEM images resulted in double-log plots of structure function, from which the determination of the fractal parameters of interest was possible. The discussion was focused on the fractal dimension D, which governs relative height variations upon scaling in length, and corner frequency f_c, which separates the scaling behavior of different-order structures (particles and their aggregates). The obtained results show that the heat treatment leaves behind a granular structure of steel (D₂ = 2.43; f_c2 = 1.97 nm), whereas corrosion tests reveal the appearance of pits (D₁ = 2.17; f_c1 = 0.303 nm; D₂ = 2.59; f_c2 = 4.76 nm). In turn, the ion nitriding improves the resistance of steel X39Cr13 to local corrosion. The fractal analysis also shows that the structure of the nitrided layer differs insignificantly from that of the untreated material, seen only as a shortening of the radius of the self-similarity area by a factor of two (f_c2 = 1 nm). Full article

(This article belongs to the Special Issue Surface Engineering for Wear Protection and Friction Reduction)

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17 pages, 5540 KiB

Open AccessArticle

Discussion of Stick-Slip Dynamics of 2DOF Sliding Systems Based on Dynamic Vibration Absorbers Analysis

by Satoru Maegawa, Xiaoxu Liu and Fumihiro Itoigawa

Lubricants 2022, 10(6), 113; https://doi.org/10.3390/lubricants10060113 - 02 Jun 2022

Cited by 1 | Viewed by 1825

Abstract

In this study, we discussed the occurrence condition stick-slip model based on a 2DOF system, in which a 1DOF system model commonly used in stick-slip analysis was attached on an elastic foundation. Specifically, the effects of the mass, stiffness, and damping coefficient of [...] Read more.

In this study, we discussed the occurrence condition stick-slip model based on a 2DOF system, in which a 1DOF system model commonly used in stick-slip analysis was attached on an elastic foundation. Specifically, the effects of the mass, stiffness, and damping coefficient of the elastic foundation on the occurrence and non-occurrence of stick-slip were investigated. It was found that when the elastic foundation parameters were determined based on the optimal parameter tuning method of the dynamic vibration absorber (DVA) theory, the range of stick-slip occurrences reduced compared to the sliding system without the elastic foundation. Full article

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16 pages, 12764 KiB

Open AccessArticle

Carbon Structures and Tribological Properties of Fe-C-SiC Self-Lubricating Metal Matrix Composites Prepared with α/β-SiC Polytypes

by Guilherme Oliveira Neves, Diego Berti Salvaro, Tatiana Bendo, Deise Rebelo Consoni, José Daniel Biasoli de Mello, Cristiano Binder and Aloisio Nelmo Klein

Lubricants 2022, 10(6), 112; https://doi.org/10.3390/lubricants10060112 - 02 Jun 2022

Cited by 4 | Viewed by 1847

Abstract

Sintered iron-based self-lubricant composites in which graphite reservoirs are generated by the dissociation of silicon carbide (SiC) particles feature low friction coefficients and scuffing resistance combined with high mechanical stress. This work evaluated the influence of the sintering temperature and the SiC polytype [...] Read more.

Sintered iron-based self-lubricant composites in which graphite reservoirs are generated by the dissociation of silicon carbide (SiC) particles feature low friction coefficients and scuffing resistance combined with high mechanical stress. This work evaluated the influence of the sintering temperature and the SiC polytype on the graphite reservoirs morphology, structure, and friction behaviour. The reservoirs were studied by field emission gun-scanning electron microscopy (FEG-SEM), micro-Raman spectroscopy, and transmission electron microscopy (TEM). The friction behaviour was evaluated by cylinder on plane tests (friction coefficient and scuffing resistance). The results showed that the SiC polytype and the sintering temperature modified the graphite structures. The SiC dissociation promoted the formation of different nano graphites, presenting different turbostratic 2D and 3D arrays. The results showed that the presence of the turbostratic graphite was beneficial to the friction behaviour of these composites, which offered better tribological performance than the composite with 3D graphite. Full article

(This article belongs to the Special Issue Friction and Wear in Composite Materials)

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17 pages, 5137 KiB

Open AccessArticle

Effects of an Electrical Double Layer and Tribo-Induced Electric Field on the Penetration and Lubrication of Water-Based Lubricants

by Zhiqiang Luan, Wenshuai Liu, Yu Xia, Ruochong Zhang, Bohua Feng, Xiaodong Hu, Shuiquan Huang and Xuefeng Xu

Lubricants 2022, 10(6), 111; https://doi.org/10.3390/lubricants10060111 - 02 Jun 2022

Cited by 5 | Viewed by 1987

Abstract

Understanding the effects of electrical double layers (EDL) and tribo-induced electric fields on the electroosmotic behaviors of lubricants is important for developing high-performance water-based lubricants. In this study, EDL conductivities of aqueous lubricants containing a surfactant of 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate (CHAPS) or cetyltrimethylammonium bromide (CTAB) [...] Read more.

Understanding the effects of electrical double layers (EDL) and tribo-induced electric fields on the electroosmotic behaviors of lubricants is important for developing high-performance water-based lubricants. In this study, EDL conductivities of aqueous lubricants containing a surfactant of 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate (CHAPS) or cetyltrimethylammonium bromide (CTAB) were analyzed. The interfacial zeta potentials of the synthesized lubricants and Al₂O₃ ceramic-alloy steel contacts were measured, and frictional potentials of ceramic and steel surfaces were determined using a modified ball-on-disc configuration. The distribution characteristics of the tribo-induced electric field of the ceramic-steel sliding contact were numerically analyzed. The electroosmotic behaviors of the lubricants were investigated using a four-ball configuration. It was found that an EDL and tribo-induced electric field was a crucial enabler in stimulating the electroosmosis of lubricants. Through altering EDL structures, CHAPS enhanced the electroosmosis and penetration of the water-based lubricant, thus resulting in improved lubrication. Full article

(This article belongs to the Special Issue Advances in Water-Based Nanolubricants)

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20 pages, 5358 KiB

Open AccessArticle

Practical Example of Modification of a Gearbox Lubrication System

by Silvia Maláková and Samuel Sivák

Lubricants 2022, 10(6), 110; https://doi.org/10.3390/lubricants10060110 - 01 Jun 2022

Cited by 1 | Viewed by 4371

Abstract

This paper presents the optimization of the lubrication method of a helical bevel gearbox, which is part of a pickling line. The first gear stage of this gearbox showed frequent failures. The bevel gearing and bearings were damaged. Damage analysis was performed, based [...] Read more.

This paper presents the optimization of the lubrication method of a helical bevel gearbox, which is part of a pickling line. The first gear stage of this gearbox showed frequent failures. The bevel gearing and bearings were damaged. Damage analysis was performed, based on which a change in bevel gearing and bearing lubrication was proposed. In this case, the original transmission was lubricated by dip lubrication. The bevel gear wheel was insufficiently submerged below the lubricating oil level. Due to insufficient lubrication of the bevel gearing, both gear wheels, the bevel pinion, and the bevel wheel were damaged. Central circulating lubrication has been proposed for the bevel gear pair and first gearbox shaft bearings. This paper deals with the design of circulating lubrication components. Changes and modifications to an existing lubrication system are proposed. The layout of the gearbox in question was not originally designed and adapted for the circulating lubrication required. To improve the original lubrication system, it was decided that it should be redesigned with central circulating lubrication, which meant implementing the necessary gearbox casing modifications. Our novel contribution is the proposition of an innovative transmission lubrication system aimed at increasing the service life parameters of the transmission. After the implementation of the proposed modifications to the lubrication method, a period of monitoring the operating characteristics of the gearbox followed. With the modification of the lubrication system of the bevel gear pair, the temperature on the gearing surface was lowered by 39%. The service life of the gearbox increased from the original 1.9 years to at least 5 years. On the basis of the long-term monitoring of changes caused by the adjustment of the lubrication method, we can state that the requirement was met, and the frequent failures of this gearbox were eliminated. Full article

(This article belongs to the Special Issue Gear Load-Independent Power Losses)

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13 pages, 8128 KiB

Open AccessArticle

Friction and Wear Characteristics of Aqueous ZrO₂/GO Hybrid Nanolubricants

by Shuiquan Huang, Zhen Wang, Longhua Xu and Chuanzhen Huang

Lubricants 2022, 10(6), 109; https://doi.org/10.3390/lubricants10060109 - 01 Jun 2022

Cited by 9 | Viewed by 1637

Abstract

Aqueous nanolubricants containing ZrO₂ nanoparticles, graphene oxide (GO) nanosheets, or hybrid nanoparticles of ZrO₂ and GO were formulated using a cost-effective ultrasonication de-agglomeration method. The friction and wear characteristics of these water-based nanolubricants were systematically investigated using a block-on-ring testing configuration [...] Read more.

Aqueous nanolubricants containing ZrO₂ nanoparticles, graphene oxide (GO) nanosheets, or hybrid nanoparticles of ZrO₂ and GO were formulated using a cost-effective ultrasonication de-agglomeration method. The friction and wear characteristics of these water-based nanolubricants were systematically investigated using a block-on-ring testing configuration with a stainless- and alloy steel contact pair. The concentrations and mass ratios of nanoadditives were varied from 0.02 to 0.10 wt.% and 1:5 to 5:1, respectively, to obtain optimal lubrication performance. The application of a 0.06 wt.% 1:1 ZrO₂/GO hybrid nanolubricant resulted in a 57% reduction in COF and a 77% decrease in wear volume compared to water. The optimised ZrO₂/GO hybrid nanolubricant was found to perform better than pure ZrO₂ and GO nanolubricant in terms of tribological performance due to its synergistic lubrication effect, which showed up to 54% and 41% reductions in friction as well as 42% and 20% decreases in wear compared with 0.06 wt.% ZrO₂ and 0.06 wt.% GO nanolubricants. The analysis of wear scars revealed that using such a ZrO₂/GO hybrid nanolubricant yielded a smooth worn surface, with 87%, 45%, and 33% reductions in S_a compared to water and 0.06 wt.% ZrO₂ and 0.06 wt.% GO nanolubricants. The superior tribological performance can be ascribed to the combination of the rolling effect of ZrO₂ nanoparticles and the slipping effect of GO nanosheets. Full article

(This article belongs to the Special Issue Advances in Water-Based Nanolubricants)

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4 pages, 192 KiB

Open AccessPerspective

Challenges in Mitigating Lubricant Foaming

by Vineeth Chandran Suja

Lubricants 2022, 10(6), 108; https://doi.org/10.3390/lubricants10060108 - 01 Jun 2022

Viewed by 1651

Abstract

Lubricant foaming and its mitigation is an active area of research driven by demands from modern machinery that require foam-free lubricant operation over extended periods and under adverse conditions. Tackling lubricant foaming has proven to be challenging due to interdependent foam stabilization mechanisms [...] Read more.

Lubricant foaming and its mitigation is an active area of research driven by demands from modern machinery that require foam-free lubricant operation over extended periods and under adverse conditions. Tackling lubricant foaming has proven to be challenging due to interdependent foam stabilization mechanisms and a multitude of antifoam inactivation routes. This perspective briefly outlines the key challenges faced by researchers in this field. Overcoming these challenges to create lubricants with superior foaming characteristics requires the development of new lubricant and antifoam chemistry as well as a shift from the existing trial-and-error methods to mechanistic-insight-driven lubricant formulation and antifoam design. Full article

18 pages, 2215 KiB

Open AccessArticle

Edge Pressures Obtained Using FEM and Half-Space: A Study of Truncated Contact Ellipses

by Michael Juettner, Marcel Bartz, Stephan Tremmel, Martin Correns and Sandro Wartzack

Lubricants 2022, 10(6), 107; https://doi.org/10.3390/lubricants10060107 - 01 Jun 2022

Cited by 3 | Viewed by 2063

Abstract

In rolling or gear contacts, truncation of the contact ellipse can occur, for example, when an undercut extends into the contact area. For an elastic calculation approach, the edge constitutes a mathematical singularity, which is revealed by a theoretically infinitely high pressure peak. [...] Read more.

In rolling or gear contacts, truncation of the contact ellipse can occur, for example, when an undercut extends into the contact area. For an elastic calculation approach, the edge constitutes a mathematical singularity, which is revealed by a theoretically infinitely high pressure peak. However, when elastic–plastic material behavior is taken into account, the pressure peak is limited by local hardening and yielding of the material, leading to plastic deformations. As a result, those calculations are rather challenging and the results partly unexpected due to the discontinuity contained in the geometry. Nevertheless, to the authors’ knowledge, hardly any published studies exist on elastic–plastic simulations of truncated contact ellipses. Therefore, a numerical study concerning the contact of a rigid ball with an elastic–plastic plane is presented. Due to an undercut in the plane, a quarter of the theoretical Hertzian contact ellipse is cut off. The aim of the study is to investigate the influence of the undercut angle on the pressure distribution and the elastic and plastic deformation at the edge. The use of FEM shows that the undercut angle has a significant effect on the characteristics of the contact. The results obtained using FEM are then used as a reference for comparison with a semi-analytical method (SAM). It is shown that the SAM, based on the half-space, provides comparable results only for very small undercut angles. Full article

(This article belongs to the Special Issue Numerical Simulations in Lubrication)

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17 pages, 5498 KiB

Open AccessArticle

Development of Universal Friction Calibration Curve for Ball Ironing Test

by Nuttakorn Sae-eaw, Sutee Olarnrithinun, Varunee Premanond and Yingyot Aue-u-lan

Lubricants 2022, 10(6), 106; https://doi.org/10.3390/lubricants10060106 - 30 May 2022

Viewed by 1547

Abstract

The friction calibration curve (FCC) is normally constructed to indirectly approximate the friction value for any simulative friction test based on sensitive friction indicators (i.e., forming load or final geometry) by finite element modeling (FEM). For calculation, these indicators are highly dependent on [...] Read more.

The friction calibration curve (FCC) is normally constructed to indirectly approximate the friction value for any simulative friction test based on sensitive friction indicators (i.e., forming load or final geometry) by finite element modeling (FEM). For calculation, these indicators are highly dependent on flow stress data and the techniques to extrapolate them. A universal FCC is preferable with the independence of these factors. In this paper, the sensitivity of the material data and our proposed extrapolation techniques for the ball ironing test (BIT) were studied to construct a new universal FCC. A specific load was proposed as a new friction indicator for this universal FCC. It was used to approximate the friction value for different materials and lubricants. This friction value was also validated to determine the maximum load and geometry for pulley forming. The results obtained from the simulation were in good agreement with the experiment. Full article

(This article belongs to the Special Issue Advances in Wear Predictive Models)

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16 pages, 5885 KiB

Open AccessArticle

Effect of Molecular Weight on Tribological Properties of Polyether Amine Derivatives under Different Contact Modes

by Wenjing Hu and Jiusheng Li

Lubricants 2022, 10(6), 105; https://doi.org/10.3390/lubricants10060105 - 27 May 2022

Cited by 3 | Viewed by 2829

Abstract

The requirements for the fuel economy of modern industry continue to drive the progress of low-viscosity lubricants. The present work reports the application of polyether amine derivatives as friction modifiers to improve the tribological properties of low viscosity poly-alpha-olefin. Three polyether amine derivatives [...] Read more.

The requirements for the fuel economy of modern industry continue to drive the progress of low-viscosity lubricants. The present work reports the application of polyether amine derivatives as friction modifiers to improve the tribological properties of low viscosity poly-alpha-olefin. Three polyether amine derivatives with different molecular weights were synthesized, the tribological properties of which were systematically investigated under three different contact modes. These functionalized polymers exhibited significant friction reduction and wear resistance properties in the point-on-flat and line-on-flat friction tests, but just showed anti-wear performance in the severe point-to-point contact mode. The results exhibited that molecular weights of the polymers had a direct effect on their tribological properties. The increase of molecular weight in a certain range was beneficial to the improvement of tribological properties, but further undue increase will rather reduce the friction reduction and wear resistance performances. It can be indicated that the number of oxygen atoms increased with the molecular weight of the polymer, which will be conductive to the adsorption of the polymer on the metal surface. However, when the molecular weight of the polymer exceeds a certain value, the steric hindrance of the molecules adsorbing to the metal surface increases, which in turn has a negative impact on the tribological properties. Full article

(This article belongs to the Special Issue Advances in Friction Modifiers and Liquid Confinement)

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Lubricants, Volume 10, Issue 6 (June 2022) – 26 articles

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