Lubricants

25 pages, 4129 KiB

Open AccessArticle

Response Modeling and Optimization of Process Parameters in Turning Medium Carbon Steel Under Minimum Quantity Lubrication (MQL) with Vegetable Oil and Oil Blends

by Indranil Das and Prianka Binte Zaman

Lubricants 2024, 12(12), 444; https://doi.org/10.3390/lubricants12120444 - 12 Dec 2024

Abstract

Machining is an important aspect of manufacturing. The application of cutting fluid in the field of engineering manufacturing has a history of hundreds of years, and it plays a vital role in the processing efficiency and surface quality of parts. The use of [...] Read more.

Machining is an important aspect of manufacturing. The application of cutting fluid in the field of engineering manufacturing has a history of hundreds of years, and it plays a vital role in the processing efficiency and surface quality of parts. The use of vegetable oil in machining operations is receiving attention currently for sustainable alternatives to mineral-based cutting oil. If the vegetable oil is applied through the minimum quantity lubrication (MQL) technique, it becomes more cost effective, eco-friendly, and sustainable. This study aims to investigate the effects (cutting force and temperature) of coconut oil, a coconut–rice bran oil blend, and a coconut–olive oil blend, and compare them with VG 68 oil using MQL. A magnetic stirrer was employed for mixing oils (coconut–rice bran oil and coconut–olive oil), performed at 40 °C and 250 rpm. The response parameter values were evaluated at different combinations of speed (78, 113.5, and 149 mm/min), feed (0.1, 0.13, and 0.16 mm/rev), and depth of cut (0.5, 0.75, and 0.1 mm). The design of the experiment (DOE) was created using the value of input parameters using response surface methodology (RSM). Percentage (%) reduction was calculated to compare the reduction in cutting force and temperature by using coconut oil, a coconut–rice bran oil blend, and a coconut–olive oil blend concerning mineral oil. Empirical models were developed for cutting force and temperature by RSM for the four cutting environments. The ANOVA result shows that the model performed satisfactorily for both temperature and force analysis. RSM-based optimization was carried out and the optimal solution was found at the cutting speed of 80.15 m/min, feed rate of 0.10 mm/min, and 0.5 mm depth of cut for the coconut–olive oil blend. Also, the model performed better in the reduction in force than temperature. Full article

(This article belongs to the Special Issue Recent Advances in Green Lubricants)

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25 pages, 10155 KiB

Open AccessArticle

Effect of Surface Roughness on the Friction Moment in a Lubricated Deep Groove Ball Bearing

by Harsh Kumar, Vaibhav Gupta, Velamala Bharath, Mayank Tiwari, Surajit Kumar Paul, Lokesh Agrawal, Arendra Pal Singh and Ayush Jain

Lubricants 2024, 12(12), 443; https://doi.org/10.3390/lubricants12120443 - 11 Dec 2024

Abstract

Deep groove ball bearings (DGBBs) are extensively utilized in industrial machinery, mechanical systems, and household appliances due to their simple design, low maintenance, and ability to operate at high speeds. A critical issue in the performance of these bearings is the power loss [...] Read more.

Deep groove ball bearings (DGBBs) are extensively utilized in industrial machinery, mechanical systems, and household appliances due to their simple design, low maintenance, and ability to operate at high speeds. A critical issue in the performance of these bearings is the power loss by internal friction torque, which adversely affects system efficiency, longevity, and reliability, particularly in demanding applications such as aviation and marine systems. The friction torque in DGBBs is influenced by factors such as load, speed, surface roughness, and lubricant viscosity, making the precise understanding of these elements essential for optimizing system efficiency. Despite its significance, the effect of surface roughness on friction torque in DGBBs remains underexplored. This paper presents an analytical model to evaluate the frictional moments resulting from interactions between the ball–race and ball–cage in lubricated, low-speed DGBBs. This model employs a mixed elastohydrodynamic lubrication approach to determine the friction coefficient at the contact interfaces. This study explores how surface roughness and speed affect both ball–race and ball–cage friction torque, offering a comprehensive analysis of their influence on overall frictional torque. Additionally, the effect of surface roughness on ball–cage contact forces is investigated, enhancing the understanding of its contribution to friction torque. These insights aim to improve DGBB design and operation, maximizing performance and energy efficiency. Full article

(This article belongs to the Special Issue Recent Advances in Lubricated Tribological Contacts)

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21 pages, 6166 KiB

Open AccessArticle

Sealing Performance Analysis of Lip Seal Ring for High-Speed Micro Bearing

by Hengdi Wang, Yulu Yue, Yongcun Cui, Xiaobiao Qiu and Chang Li

Lubricants 2024, 12(12), 442; https://doi.org/10.3390/lubricants12120442 - 11 Dec 2024

Abstract

This article focuses on the problem of sealing failure in high-speed micro bearings. Based on a thermal-stress coupled finite element model, the distribution of equivalent stress and contact pressure of the sealing ring and the influence of various factors on the sealing performance [...] Read more.

This article focuses on the problem of sealing failure in high-speed micro bearings. Based on a thermal-stress coupled finite element model, the distribution of equivalent stress and contact pressure of the sealing ring and the influence of various factors on the sealing performance are analyzed. Based on this, the Latin Hypercube sampling method, Kriging surrogate model and genetic algorithm are used to find the optimal combination of sealing performance. Finally, the accuracy of the model and method is verified through orthogonal experiments. Research has found that the maximum equivalent stress of the seal ring is 0.59234 MPa, and it increases first and then decreases with the increase in lip inclination angle, friction coefficient and radial interference amount, increases with the increase in lubricant temperature, and decreases with the increase in bearing rotation speed. The maximum contact pressure is 0.20433 MPa, and it decreases with the increase in the lip inclination angle, increases first and then decreases with the increase in the friction coefficient, and decreases first and then increases with the increase in the lubricant temperature, bearing rotation speed and radial interference amount. The most significant factor affecting the equivalent stress of the seal ring is the lubricant temperature, and the most significant factor affecting the contact stress is the interference fit amount. When the seal lip inclination angle is 43.99°, the friction coefficient is 0.01 mm, the lubricant temperature is 111.5 °C, the bearing rotation speed is 28,853 rpm and the radial interference amount is 0.04 mm, the sealing performance of the sealing ring is optimal. Full article

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23 pages, 5711 KiB

Open AccessArticle

Modeling and Dynamic Analysis of Double-Row Angular Contact Ball Bearing–Rotor–Disk System

by Haibiao Zhang, Zhen Li, Haijian Liu, Tao Liu and Qingshan Wang

Lubricants 2024, 12(12), 441; https://doi.org/10.3390/lubricants12120441 - 10 Dec 2024

Abstract

This article presents a general numerical method to establish a mathematical model of a bearing–rotor–disk system. This mathematical model consists of two double-row angular contact ball bearings (DRACBBs), a rotor and a rigid disk. The mathematical model of the DRACBB is built on [...] Read more.

This article presents a general numerical method to establish a mathematical model of a bearing–rotor–disk system. This mathematical model consists of two double-row angular contact ball bearings (DRACBBs), a rotor and a rigid disk. The mathematical model of the DRACBB is built on the basis of elastic Hertz contact by adopting the Newton Raphson iteration method, and three different structure forms are taken into account. The rotor is modeled by employing a finite element method in conjunction with Timoshenko beam theory, and the rigid disk is modeled by applying the lumped parameter method. The mathematical model of the bearing–rotor–disk system is constructed by the coupling of the bearing, rotor and disk, and the dynamic response of the bearing–rotor–disk system can be solved by employing the Newmark-β method. The validation of the above mathematical model is demonstrated by comparing the proposed results with the results from the existing literature and finite element software. The dynamic characteristics of the DRACBBs and the dynamic response of the bearing–rotor–disk system are investigated by parametric study. A dynamic characteristic analysis of the DRACBB is conducted to ensure the optimal structure form of the DRACBB under complex external loads, and it can provide a reference for the selection of the structural forms of DRACBBs. Full article

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17 pages, 45748 KiB

Open AccessFeature PaperArticle

Utilization of Magnetic Fraction Isolated from Steel Furnace Slag as a Mild Abrasive in Formulation of Cu-Free Friction Composites

by Vlastimil Matějka, Priyadarshini Jayashree, Kryštof Foniok, Jozef Vlček, Petra Matějková and Giovanni Straffelini

Lubricants 2024, 12(12), 440; https://doi.org/10.3390/lubricants12120440 - 10 Dec 2024

Abstract

Magnetic fraction isolated from steel furnace slag was tested as a component of Cu-free friction composites. The friction–wear performance and production of wear particles during their testing using a pin-on-disc tester against a cast iron disc were evaluated. To compare the effect of [...] Read more.

Magnetic fraction isolated from steel furnace slag was tested as a component of Cu-free friction composites. The friction–wear performance and production of wear particles during their testing using a pin-on-disc tester against a cast iron disc were evaluated. To compare the effect of the magnetic fraction on the parameters studied, the composite with alumina and the composite with original steel furnace slag were also prepared and tested. All composites showed a comparable friction coefficient. The composite with original steel furnace slag, and the composite with a magnetic fraction showed higher wear resistance compared to the composite containing alumina. The positive effect of the magnetic fraction on the extent of the emission of wear particles was observed and explained by the decreased aggressiveness of this composite to the cast iron disc. The influence of the phase composition of the steel furnace slag and the magnetic fraction on the friction film formation was also indicated, and its effect on the production of wear particles was proposed. Full article

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Graphical abstract

17 pages, 16276 KiB

Open AccessArticle

Effect of Counterbody Material on the Boundary Lubrication Behavior of Commercially Pure Titanium in a Motor Oil

by Yizhao Liu, Mohammed Al-Shan, Richard Bailey and Yong Sun

Lubricants 2024, 12(12), 439; https://doi.org/10.3390/lubricants12120439 - 10 Dec 2024

Abstract

Titanium possesses many useful properties and is a technologically important material in engineering. However, lubrication of titanium has long been a problem that has prevented titanium from being more widely used. This is due to its poor tribological properties, deriving from its high [...] Read more.

Titanium possesses many useful properties and is a technologically important material in engineering. However, lubrication of titanium has long been a problem that has prevented titanium from being more widely used. This is due to its poor tribological properties, deriving from its high tendency towards adhesive wear, material transfer, and abrasive wear. Lubrication is a system engineering which involves material combinations, material surfaces, lubricants, and operating conditions as a system. In this work, the boundary lubrication behavior of commercially pure titanium (CP-Ti) sliding against various counterbody materials in a motor oil (0W-30) was investigated under ball-on-plate reciprocating sliding conditions. The counterbody materials (balls) include CP-Ti, ceramic (Al₂O₃), steel (AISI 52100), and polymer (nylon). The results show that depending on material combination, the lubricating behavior can be divided into three categories, i.e., (1) lubrication failure (Ti-Ti), (2) improved lubrication but with friction instability (Ti-Al₂O₃), and (3) effective lubrication (Ti–steel and Ti–nylon). Lubrication failure of the Ti-Ti pair leads to high and unstable friction and severe wear from both the plate and ball, while friction instability of the Ti-Al₂O₃ pair leads to friction spikes and high wear rates. Effective lubrication of the Ti–steel pair results in low and smooth friction and much-reduced wear rates of the Ti plate by nearly 10,000 times. However, there is a load-dependence of the lubrication effectiveness of the Ti–steel pair. Although the Ti–nylon pair is effectively lubricated in terms of much-reduced friction, the nylon ball suffers from severe wear. The friction and wear mechanisms of the various sliding pairs are discussed in this paper. Full article

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11 pages, 3788 KiB

Open AccessArticle

Ceramic–Ceramic Hip Implants: Investigation of Various Factors Associated with Squeaking

by Stefan Schroeder, Luisa Gaedeke, Mustafa Hariri, Therese Bormann, Maurice Weiss, Jan Philippe Kretzer and Maximilian Uhler

Lubricants 2024, 12(12), 438; https://doi.org/10.3390/lubricants12120438 - 9 Dec 2024

Abstract

Despite the low wear rate of ceramic–ceramic hip implants, hard-on-soft bearings remain the most commonly used bearings in North America and Western Europe. A major concern with ceramic–ceramic hip implants is the occurrence of squeaking phenomena, which are still not fully understood. Various [...] Read more.

Despite the low wear rate of ceramic–ceramic hip implants, hard-on-soft bearings remain the most commonly used bearings in North America and Western Europe. A major concern with ceramic–ceramic hip implants is the occurrence of squeaking phenomena, which are still not fully understood. Various factors are mentioned in the literature, but currently, studies mostly focus on only one specific parameter. The goal of this study was to systematically analyze four different factors (cup orientation, protein concentration of the test fluid, contact pressure and head roughness) that may influence the squeaking behavior of this bearing type. An in vitro simulation according to ISO 14242-1 was performed using an AMTI Vivo simulator, and acoustic signals were recorded. No squeaking occurred for any of the four parameters when bovine serum or water was used as the test fluid. Squeaking was observed only under dry conditions with the ceramic–ceramic bearing. Under dry conditions, the maximum resulting torque increased steadily, and squeaking occurred after approximately 300 cycles at a resulting torque of more than 22 Nm. Thus, the resulting torque might be one factor leading to squeaking and should be kept low to reduce the risk of squeaking. Full article

(This article belongs to the Special Issue Biomechanics and Tribology)

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24 pages, 6499 KiB

Open AccessArticle

Sliding Contact Fatigue Damage of Metallic Implants in a Simulated Body Fluid Environment

by Mihir V. Patel, Edward Cudjoe and Jae Joong Ryu

Lubricants 2024, 12(12), 437; https://doi.org/10.3390/lubricants12120437 - 8 Dec 2024

Abstract

At the modular interface of the joint implants, repeated contact stresses in a corrosive synovial environment cause surface degradation that worsens over time. The lubricating mechanisms at the joints are altered by the deteriorated synovial fluid by the wear debris and corrosion products. [...] Read more.

At the modular interface of the joint implants, repeated contact stresses in a corrosive synovial environment cause surface degradation that worsens over time. The lubricating mechanisms at the joints are altered by the deteriorated synovial fluid by the wear debris and corrosion products. As a result, the joint implants’ unsatisfactory performance will be exacerbated by the synergistic combination of wear and corrosion. In this work, reciprocal sliding contact tests in simulated synovial fluid were conducted on the two main metallic implant materials, CoCrMo and Ti6Al4V. The mechanical and electrochemical reactions were described by monitoring the open-circuit potential (OCP) and coefficient of friction (COF). The electrochemical damage that altered the oxidation chemistry on both surfaces was illustrated by the potentiostatic test findings. The surface damage process of CoCrMo under all contact loads presented unstable chemomechanical responses. On the other hand, the Ti6Al4V results revealed a moderate decrease in fretting current and stable changes in the coefficient of friction. Consequently, the experimental investigation determined that, when mechanical loadings and electrochemical stimulus are combined, Ti6Al4V’s biocompatibility would be superior to CoCrMo’s. Full article

(This article belongs to the Special Issue Biomechanics and Tribology)

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17 pages, 5396 KiB

Open AccessArticle

Fumed Silica in Coconut Oil Based Nanofluids for Cooling and Lubrication in Drilling Applications

by Jesús J. Jiménez-Galea and Ana Isabel Gómez-Merino

Lubricants 2024, 12(12), 436; https://doi.org/10.3390/lubricants12120436 - 8 Dec 2024

Abstract

Virgin coconut oil (VCO) is an edible vegetable oil that is eco-friendly, biodegradable, and sustainable, with high thermal and chemical stability as a phase change material (PCM). In this work, VCO filled with fumed silica A200 nanoparticles was tested as a cutting fluid [...] Read more.

Virgin coconut oil (VCO) is an edible vegetable oil that is eco-friendly, biodegradable, and sustainable, with high thermal and chemical stability as a phase change material (PCM). In this work, VCO filled with fumed silica A200 nanoparticles was tested as a cutting fluid in drilling processes. Silica concentrations ranging from 1 to 4 vol% were analyzed. Thermal properties were evaluated by differential scanning calorimetry (DSC) and thermal conductivity measurements at different temperatures and concentrations. Thermal conductivity showed an enhancement with the addition of silica powder and reduced with increasing temperature. Based on thermal and flow properties, VCO-3A200 was found to be the optimal concentration. The thermal images of this nanofluid taken after 60 s of drilling exhibited a reduction of 12 °C with respect to the dry process. The friction coefficient versus shear rate was also measured. With 8% VCO, a reduction in the friction coefficient of 8% compared to the dry test was achieved. The addition of 3 vol% of silica to the base oil reduced the friction coefficient by 16% compared to the dry test. The use of fumed silica dispersed in VCO has proven to be a sustainable, recyclable, and environmentally friendly refrigerant and lubricant cutting fluid. Full article

(This article belongs to the Special Issue Advances in Sustainable Cooling/Lubrication Techniques for Improving the Tribological Characteristics and Machining Performance)

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15 pages, 97256 KiB

Open AccessArticle

In Situ Operando Indicator of Dry Friction Squeal

by Maël Thévenot, Jean-François Brunel, Florent Brunel, Maxence Bigerelle, Merten Stender, Norbert Hoffmann and Philippe Dufrénoy

Lubricants 2024, 12(12), 435; https://doi.org/10.3390/lubricants12120435 - 8 Dec 2024

Abstract

In various applications, dry friction could induce vibrations. A well-known example is frictional braking systems in ground transportation vehicles involving a sliding contact between a rotating and a stationary part. In such scenarios, the emission of high-intensity noise, commonly known as squeal, can [...] Read more.

In various applications, dry friction could induce vibrations. A well-known example is frictional braking systems in ground transportation vehicles involving a sliding contact between a rotating and a stationary part. In such scenarios, the emission of high-intensity noise, commonly known as squeal, can present human health risks based on the noise’s intensity, frequency, and occurrences. Despite the importance of squeal in the context of advancing urbanization, the parameters determining its occurrence remain uncertain due to the complexity of the involved phenomena. This study aims to identify a relevant operando indicator for predicting squeal occurrences. To this end, a pin-on-disc test rig was developed to replicate various contact conditions found in road profiles and investigate resulting squealing. Each test involves a multimodal instrumentation, complemented by surface observations. It is illustrated that the enhanced thermal indicator identified is relevant because it is sensitive to the thermomechanical and tribological phenomena involved in squealing. Full article

(This article belongs to the Special Issue Tribology in Vehicles)

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10 pages, 2799 KiB

Open AccessArticle

The Temperature Dependence of Divergence Pressure

by Scott Bair

Lubricants 2024, 12(12), 434; https://doi.org/10.3390/lubricants12120434 - 6 Dec 2024

Abstract

The so-called controversy in elastohydrodynamic lubrication (EHL) regarding the nature of the shear dependence of viscosity, Eyring versus Carreau, is truly a controversy regarding the pressure and temperature dependence of low-shear viscosity. Roelands removed data that contradicted his claims of accuracy for his [...] Read more.

The so-called controversy in elastohydrodynamic lubrication (EHL) regarding the nature of the shear dependence of viscosity, Eyring versus Carreau, is truly a controversy regarding the pressure and temperature dependence of low-shear viscosity. Roelands removed data that contradicted his claims of accuracy for his correlation. The Roelands hoax became acceptable in EHL because ignoring the universal previtreous piezoviscous response made the traction calculated with the Eyring assumption appear to be reasonable. Traction and minimum film thickness calculations sometimes require the description of viscosity at pressures up to the glass transition pressure. There have been few measurements of viscosity at pressures up to glass pressure. Therefore, a need exists for a piezoviscous model that extrapolates accurately, and the Hybrid model fills that need. Here, an improved relation for the temperature dependence of divergence pressure is offered and extrapolation is demonstrated for a polyalphaolefin and propylene carbonate. A linear dependence of divergence pressure with temperature is more useful than previous versions. An improvement in the capability of high-pressure viscometry is suggested based upon the fractional Stokes Einstein Debye relation and the relatively simple measurements of DC conductivity. Full article

(This article belongs to the Special Issue Recent Advances in Lubricated Tribological Contacts)

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14 pages, 8524 KiB

Open AccessArticle

Levitation Performance of Radial Film Riding Seals for Gas Turbine Engines

by Syed Muntazir Mehdi, Young Cheol Kim and Eojin Kim

Lubricants 2024, 12(12), 433; https://doi.org/10.3390/lubricants12120433 - 5 Dec 2024

Abstract

Turbomachinery in gas turbines uses seals to control the leakage between regions of high and low pressure, consequently enhancing engine efficiency and performance. A film riding seal hybridizes the advantages of contact and non-contact seals, i.e., low leakage and low friction and wear. [...] Read more.

Turbomachinery in gas turbines uses seals to control the leakage between regions of high and low pressure, consequently enhancing engine efficiency and performance. A film riding seal hybridizes the advantages of contact and non-contact seals, i.e., low leakage and low friction and wear. The literature focuses on the leakage performance of these seals; however, one of their fundamental characteristics, i.e., the gap between the rotor and seal surface, is scarcely presented. The seal pad levitates due to the deflection of the springs at its back under the influence of hydrodynamic forces. This study develops a test rig to measure the levitation of film riding seals. A high-speed motor rotates the rotor and gap sensors measure the levitation of the seal pads. Measurements are also compared with the predictions from a Reynolds equation-based theoretical model. Tests performed for the increasing rotor speed indicated that, initially, until a certain rotor speed, the pads adjust their position, then rub against the rotor until another rotor speed is reached, before finally starting levitating with further increased rotor speeds. Moreover, both the measured and predicted results show that pads levitated the most when located 90° clockwise from the positive horizontal axis (bottom of seal housing) compared to other circumferential positions. Full article

(This article belongs to the Special Issue Thermal Hydrodynamic Lubrication)

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12 pages, 4690 KiB

Open AccessArticle

Numerical Analysis of the Trapping Effect of Grooves with Various Cross-Sectional Shapes and Reynolds Numbers

by Sung-Ho Hong

Lubricants 2024, 12(12), 432; https://doi.org/10.3390/lubricants12120432 - 5 Dec 2024

Abstract

This study searches for an effective cross-sectional shape of grooves by evaluating their trapping effect using numerical methods. Grooves are widely employed to enhance lubrication performance across various systems, including in bearings and valves, where they serve multiple functions, such as improving load-carrying [...] Read more.

This study searches for an effective cross-sectional shape of grooves by evaluating their trapping effect using numerical methods. Grooves are widely employed to enhance lubrication performance across various systems, including in bearings and valves, where they serve multiple functions, such as improving load-carrying capacity, addressing pressure imbalances, storing lubricant, and minimizing leakage. Beyond these roles, grooves are crucial in preventing three-body abrasive wear by capturing solid particles, such as wear debris, within the system. This study specifically focuses on the trapping effect of grooves, examining how variations in their cross-sectional shape and the Reynolds number of the lubricant used influence this effect. To evaluate the groove’s trapping capability, the study analyzed particle trajectories and streamlines within the groove, as well as the number of particles effectively trapped. The results indicate that grooves with certain cross-sectional shapes, particularly those generating multiple vortices and small eddy currents, demonstrate superior trapping effectiveness. These findings contribute to the design of more efficient grooves in lubrication systems, providing insights into how groove geometry can be optimized to enhance the performance and longevity of mechanical components by mitigating wear through effective particle entrapment. This research has potential applications in the design and improvement of lubrication systems where managing wear and enhancing efficiency are critical concerns. Full article

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14 pages, 4313 KiB

Open AccessArticle

Dynamic Analysis of Radial Journal Bearing-Rotor System Based on the Meshless Barycentric Rational Interpolation Collocation Method

by Hongwei Zhang and Rahmatjan Imin

Lubricants 2024, 12(12), 431; https://doi.org/10.3390/lubricants12120431 - 4 Dec 2024

Abstract

This study focuses on a rigid rotor supported by radial journal bearings. Initially, models for the unsteady oil film force in bearing lubrication and the dynamics of the bearing-rotor system are established. Subsequently, the Reynolds equation for dynamic lubricating oil films is discretely [...] Read more.

This study focuses on a rigid rotor supported by radial journal bearings. Initially, models for the unsteady oil film force in bearing lubrication and the dynamics of the bearing-rotor system are established. Subsequently, the Reynolds equation for dynamic lubricating oil films is discretely solved using the meshless barycentric rational interpolation collocation method. By combining this with the equation of motion for the axis orbit, the oil film pressure distribution, the dynamic response of the rotor, and the axis orbit are calculated. Furthermore, the study investigates the dynamic response of the rotor at different rotational speeds, both with and without considering unbalanced loads. Finally, the influence of step load on the stability of rotor motion is analyzed, revealing that applying an appropriate step load to the rotor can effectively mitigate the lubricating oil films oscillation conditions. The findings of this study hold significant reference value and practical utility for engineering applications. Full article

(This article belongs to the Special Issue New Conceptions in Bearing Lubrication and Temperature Monitoring)

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21 pages, 7163 KiB

Open AccessArticle

Tribological Performance of Glycerol-Based Hydraulic Fluid Under Low-Temperature Conditions

by Paul Okhiria, Marcus Björling, Pontus Johansson, Mushfiq Hasan, Roland Larsson and Yijun Shi

Lubricants 2024, 12(12), 430; https://doi.org/10.3390/lubricants12120430 - 4 Dec 2024

Abstract

This study evaluated the tribological performance of a glycerol-based hydraulic fluid as a green alternative to conventional mineral-based hydraulic lubricants under low-temperature conditions, down to −20 °C. The performance of the glycerol hydraulic fluid (GHF) was compared against that of a mineral hydraulic [...] Read more.

This study evaluated the tribological performance of a glycerol-based hydraulic fluid as a green alternative to conventional mineral-based hydraulic lubricants under low-temperature conditions, down to −20 °C. The performance of the glycerol hydraulic fluid (GHF) was compared against that of a mineral hydraulic fluid (MHF) using an SRV tribometer for steel-to-steel sliding contact under boundary lubrication conditions. Comparisons were also made at a moderate temperature to assess the fluids’ performance across different thermal conditions. The results show that the GHF demonstrated up to 55% lower friction coefficients under various test conditions than the MHF. With wear volumes up to 90% lower, the GHF produced thinner and less intense wear scars on the test discs compared to the deeper and more pronounced scars observed with the MHF. We conducted rheological tests which also revealed the green fluid’s stable viscosity transition with temperature changes and its Newtonian behaviour under the measured shear conditions, which may indicate its ability to maintain consistent lubrication. Full article

(This article belongs to the Special Issue Recent Advances in Lubricated Tribological Contacts)

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14 pages, 4233 KiB

Open AccessArticle

Influence of Molybdenum Addition on the Structure, Mechanical Properties, and Cutting Performance of AlTiN Coatings

by Tao Yang, Jun Yin, Puyou Ying, Changhong Lin, Ping Zhang, Jianbo Wu, Alexander Kovalev, Min Huang, Tianle Wang, Andrei Y. Grigoriev, Dmitri M. Gutsev and Vladimir Levchenko

Lubricants 2024, 12(12), 429; https://doi.org/10.3390/lubricants12120429 - 3 Dec 2024

Abstract

Though AlTiN coating has been intensively studied, there is still a need to develop AlTiN coating to meet the growing demand of industrial machining. One effective way to improve the performance of AlTiN coating is by adding alloying elements. In this study, AlTiN [...] Read more.

Though AlTiN coating has been intensively studied, there is still a need to develop AlTiN coating to meet the growing demand of industrial machining. One effective way to improve the performance of AlTiN coating is by adding alloying elements. In this study, AlTiN and AlTiMo coatings were deposited using multi-arc ion plating to investigate the influence of molybdenum addition on the structure, mechanical properties, and cutting performance of AlTiN coatings. Spherical droplets formed on the surfaces of both coatings, with the AlTiMoN coating exhibiting more surface defects than the AlTiN coating. The grazing incidence X-ray diffraction results revealed the formation of an (Al,Ti)N phase formed in the AlTiN and AlTiMoN coatings. Molybdenum doping in the AlTiMoN coating slightly reduced the grain size. Both coatings exhibited excellent adhesion to the substrate. The hardness (H), elastic moduli (E), H/E, and H³/E² ratios of the AlTiMoN coating were higher than those of the AlTiN coating. The improvement in the mechanical properties was attributed to grain refinement and solution strengthening. Molybdenum doping improved the tribological properties and cutting performance of the AlTiN coatings, which was ascribed to the formation of MoO₃ as a solid lubricant. These results show a path to increase the performance of AlTiN coating through molybdenum addition and provide ideas for the application of AlTiMoN coatings for cutting tools. Full article

(This article belongs to the Special Issue Wear-Resistant Coatings and Film Materials)

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16 pages, 1946 KiB

Open AccessArticle

Multi-Objective Optimization of Friction Stir Processing Tool with Composite Material Parameters

by Aniket Nargundkar, Satish Kumar and Arunkumar Bongale

Lubricants 2024, 12(12), 428; https://doi.org/10.3390/lubricants12120428 - 2 Dec 2024

Abstract

Compared to base aluminum alloys, the surface composites of aluminum alloys are more widely used in the automotive, aerospace, and other industries. The ability to yield enhanced physical properties and a smoother microstructure has made friction stir processing (FSP) the method of choice [...] Read more.

Compared to base aluminum alloys, the surface composites of aluminum alloys are more widely used in the automotive, aerospace, and other industries. The ability to yield enhanced physical properties and a smoother microstructure has made friction stir processing (FSP) the method of choice for developing aluminum-based surface composites in recent times. In this work, the Goal Programming (GP) approach is adopted for the Multi-Objective Optimization of FSP processes with three Artificial Intelligence (AI)-based metaheuristics, viz., Artificial Bee Colony (ABC), Particle Swarm Optimization (PSO), and Teaching–Learning-Based Optimization (TLBO). Three parameters, copper percentage (Cu%), graphite percentage (Gr%), and number of passes, are considered, and multi-factor non-linear regression prediction models are developed for the three responses, Tool Vibrations, Power Consumption, and Cutting Force. The TLBO algorithm outperformed the ABC and PSO algorithms in terms of solution quality and robustness, yielding significant improvements in tool life. The results with TLBO were improved by 20% and 14% compared to the PSO and ABC algorithms, respectively. This proves that the TLBO algorithm performed better compared with the ABC and PSO algorithms. However, the computation time required for the TLBO algorithm is higher compared to the ABC and PSO algorithms. This work has opened new avenues towards applying the GP approach for the Multi-Objective Optimization of FSP tools with composite parameters. This is a significant step towards toll life improvement for the FSP of composite alloys, contributing to sustainable manufacturing. Full article

(This article belongs to the Special Issue Advances in Tool Wear Monitoring 2024)

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23 pages, 10472 KiB

Open AccessArticle

Impact of Influence of Piston Design Parameters on the Hydrodynamic Characteristics of Internal Combustion Engines—A Numerical Study

by Brahim Menacer, Sunny Narayan, Víctor Tuninetti, Tawfiq Khatir, Angelo Oñate, Liomnis Osorio, Shitu Abubakar, Joseph Samuel, Ivan Grujic, Nadica Stojanovic and Muhammad Usman Kaisan

Lubricants 2024, 12(12), 427; https://doi.org/10.3390/lubricants12120427 - 2 Dec 2024

Abstract

Piston top rings in the combustion engine play a crucial role in the overall hydrodynamic performance of engines, such as power loss, minimum film thickness and friction forces, by ensuring sealing and minimizing the leakage of burnt gases. This present paper examines the [...] Read more.

Piston top rings in the combustion engine play a crucial role in the overall hydrodynamic performance of engines, such as power loss, minimum film thickness and friction forces, by ensuring sealing and minimizing the leakage of burnt gases. This present paper examines the influence of four key parameters of the top ring, such as ring width, ring temperature, ring tension, and ring surface roughness on the hydrodynamic behavior at the ring/cylinder contact. These parameters play a significant role in the formation and maintenance of the oil film, directly influencing hydrodynamic indicators such as the minimum oil film thickness, friction force, power loss, oil pressure, and the ring angle twist. This article relies on hydrodynamic models and numerical simulations performed using GT-SUITE version 6 software to analyze these effects. The pressure curve used in this simulation is experimentally validated for an engine speed of 2000 RPM. It was found that an increase in the top ring temperature reduces the oil’s viscosity, decreasing the film thickness and increasing the risk of metal-to-metal contact. Increasing the roughness of the ring enhances oil film stability, especially at the bottom dead center (BDC) points during each phase of the operating cycle. Further, three different types of ring profiles were investigated for friction forces by varying the speed of the engine. Full article

(This article belongs to the Special Issue Advances in Hydrodynamic Friction in Combustion Engines)

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12 pages, 5147 KiB

Open AccessArticle

Tribological Properties of Polydimethylsiloxane Grafted with Poly(Ethylene Glycol) Methyl Ether Methacrylate Under Water Lubrication

by Tae-Hyeong Kim and Dae-Eun Kim

Lubricants 2024, 12(12), 426; https://doi.org/10.3390/lubricants12120426 - 2 Dec 2024

Abstract

Polydimethylsiloxane (PDMS) is a polymer material characterized by its flexibility, biocompatibility, non-toxicity, excellent stability, and high transparency. It is also easy to process and allows for control over its physical properties. However, its inherent hydrophobicity limits its application in certain fields. To address [...] Read more.

Polydimethylsiloxane (PDMS) is a polymer material characterized by its flexibility, biocompatibility, non-toxicity, excellent stability, and high transparency. It is also easy to process and allows for control over its physical properties. However, its inherent hydrophobicity limits its application in certain fields. To address this limitation, research is being conducted to modify the surface properties of PDMS through polymer grafting. In this work, poly(ethylene glycol) methyl ether methacrylate (mPEG-MA) was grafted onto the PDMS surface to convert its hydrophobic characteristics to hydrophilicity. The tribological properties of the modified PDMS were then evaluated under conditions of hydrophilicity and water lubrication. Polymer grafting was performed by generating radicals on the surface of PDMS through ultraviolet (UV) irradiation using a photoinitiator, followed by grafting with mPEG-MA. The water contact angle, which serves as an indicator of hydrophilicity, was measured and revealed a decrease in the contact angle as the conditions for mPEG-MA grafting were intensified, signifying an increase in hydrophilicity. Additionally, the tribological properties under water lubrication improved with a higher degree of mPEG-MA grafting. Notably, PDMS grafted with a 20 wt.% mPEG-MA aqueous solution via UV irradiation for 12 h consistently maintained a coefficient of friction (COF) of less than 0.02 under water lubrication. Surface damage was observed locally in the dimples only under a load of 3 N. Full article

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