Lubricants

0 pages, 23314 KiB

Open AccessArticle

Influencing Factors on the Fluting in an Axial Ball Bearing at DC Bearing Currents

by Omid Safdarzadeh, Resat Capan, Michel Werner, Andreas Binder and Oliver Koch

Lubricants 2023, 11(10), 455; https://doi.org/10.3390/lubricants11100455 - 23 Oct 2023

Cited by 1 | Viewed by 1500

The effect of variable DC bearing current amplitude, bearing current polarity, mechanical force, rotation speed, bearing temperature, and number of the balls on the fluting in an axial ball bearing type 51208 is investigated under DC currents. The results are obtained from two [...] Read more.

The effect of variable DC bearing current amplitude, bearing current polarity, mechanical force, rotation speed, bearing temperature, and number of the balls on the fluting in an axial ball bearing type 51208 is investigated under DC currents. The results are obtained from two different test setups with two different lubricants (mineral-oil-based grease and polyglycol oil). The speed varies between 100 rpm and 2000 rpm, the axial bearing force between 200 N and 2400 N, the DC current amplitude between 0.5 A and 20 A, the bearing temperature between 29 °C and 80 °C, the number of steel balls per bearing between 3 and 15, and the test duration between 6 h and 168 h. The results show that with a higher bearing current density and/or a higher bearing speed, a lower bearing force and/or a lower bearing temperature, a bigger number of roller elements, but also at a negative polarity of a DC electric bearing current, the occurring of fluting is more probable and occurs at an earlier stage of operation. Full article

(This article belongs to the Special Issue Behavior of Lubricated Bearings in Electric Circuits)

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12 pages, 4839 KiB

Open AccessArticle

Investigation of Mechanical Properties of Grey Cast Irons Reinforced with Carbon Titanium Nitride (TiNC)

by Rifat Yakut

Lubricants 2023, 11(10), 454; https://doi.org/10.3390/lubricants11100454 - 22 Oct 2023

Viewed by 1731

Abstract

In this study, grey cast iron (GG25) was produced via reinforcement with carbon titanium nitride (TiNC) in different amounts (0%, 0.153%, 0.204% and 0.255%). Samples were made from this material according to the standards for hardness, compression and wear, and then experiments were [...] Read more.

In this study, grey cast iron (GG25) was produced via reinforcement with carbon titanium nitride (TiNC) in different amounts (0%, 0.153%, 0.204% and 0.255%). Samples were made from this material according to the standards for hardness, compression and wear, and then experiments were conducted. The test conditions applied for the TiNC-reinforced samples were similarly applied to unreinforced samples. The TiNC-reinforced and unreinforced samples were compared regarding their compression, hardness, and wear properties. The results of the hardness tests showed the highest average hardness value of 215 HB for sample A (0% TiNC). For TiNC-reinforced specimens, the hardness values of the reinforced specimens increased with increasing reinforcement. Sample B (0.153% TiNC) had an average hardness value of 193 HB. For sample C (0.204% TiNC), an average hardness value of 200 HB was measured. For sample D (0.255% TiNC), an average hardness value of 204 HB was determined. Sample A’s highest compression strength value was 780 MPA (0% TiNC). Similar to the hardness test values, the compression strength of the reinforced samples increased with the increasing reinforcement rate. The compression test value was found to be 747 MPa for sample B (0.153% TiNC), 765 MPa for sample C (0.204% TiNC) and 778 MPa for sample D (0.255% TiNC). Wear tests were performed on all samples to examine changes in the wear volume loss, wear rate and friction coefficients. Scanning electron microscopy (SEM) was used to determine the wear mechanisms on the worn surfaces of the samples. When examining the wear condition of the samples with the same hardness value as a function of increasing load values, increases in the wear volume loss values were observed as the load value increased. Full article

(This article belongs to the Special Issue Frictional Behavior and Wear Performance of Cast Irons)

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21 pages, 10249 KiB

Open AccessArticle

Nonlinear Dynamic Responses of Rigid Rotor Supported by Thick Top Foil Bearings

by Bin Hu, Xiaodong Yang, Anping Hou, Rui Wang, Zhiyong Wu, Qifeng Ni and Zhong Li

Lubricants 2023, 11(10), 453; https://doi.org/10.3390/lubricants11100453 - 20 Oct 2023

Viewed by 974

Abstract

This study focuses on thick top foil bearings (TTFBs), which can prevent top foil from sagging and significantly reduce the load capacity of gas foil bearings (GFBs). However, the limited research on the dynamic responses of TTFB-rotor systems has hindered their wide application [...] Read more.

This study focuses on thick top foil bearings (TTFBs), which can prevent top foil from sagging and significantly reduce the load capacity of gas foil bearings (GFBs). However, the limited research on the dynamic responses of TTFB-rotor systems has hindered their wide application of TTFBs with high load capacity. To address this, an integrated nonlinear dynamic model is developed to analyze the linear dynamic responses of a rigid rotor supported on TTFBs. The model incorporates time domain orbit simulation, considering unsteady Reynolds equations, foil deformation equations, thick top foil motion equations, and rotor motion equations. A symmetrical test rig is used to validate the model, and three types of TTFBs with different bump foil stiffness are tested, with experimental results aligning with the model predictions. This study also investigates the effects of nominal clearance, static load, and unbalance on TTFB-rotor systems. The results indicate that unbalance has minimal impact on subsynchronous vibrations. However, larger bump foil stiffness, increased normal clearance, and higher static load contribute to improved stability and higher maximum stable speed of the TTFB-rotor system. Moreover, other relevant parameters reducing the bearing attitude angle can further enhance the system’s stability. Full article

(This article belongs to the Special Issue Advances in Bearing Lubrication and Thermodynamics 2023)

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18 pages, 9058 KiB

Open AccessArticle

Use of Functionalized Graphene-Based Materials on Grease

by Eduardo Tomanik, Paulo Berto, Wania Christinelli, Gabriela Papoulias, Xavier Raby and Valdirene Peressinotto

Lubricants 2023, 11(10), 452; https://doi.org/10.3390/lubricants11100452 - 20 Oct 2023

Cited by 2 | Viewed by 1606

Abstract

The growing awareness of reduced friction losses and new demands for electrical powertrains demand improved lubricants. Due to their unique properties, such as high thermal and electrical conductivity, graphene and its derivatives have been investigated for tribological applications, especially as lubricant additives. In [...] Read more.

The growing awareness of reduced friction losses and new demands for electrical powertrains demand improved lubricants. Due to their unique properties, such as high thermal and electrical conductivity, graphene and its derivatives have been investigated for tribological applications, especially as lubricant additives. In this work, we investigated three commercially available graphene variants, one comprising a few layers and the other two comprising nanoplates, after functionalization as additives to lithium soap grease. The grease temperature dropping point increased by approximately 6 °C. Additionally, during the reciprocating friction test, friction increased with the test duration for the baseline grease, whereas it decreased for the ones containing graphene-based additives. On the test end, friction was reduced by 8% compared to the baseline grease. On a four-ball tribometer, the wear scar was reduced from 10 to 18% compared to the baseline grease. In general, no significant difference was seen between the three graphene-based variants. The promising results found with graphene nanoplates, a less expensive material than a few graphene layers, creates opportunities for a cost-competitive additive to commercial greases. Full article

(This article belongs to the Special Issue Tribology in Mobility, Volume II)

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15 pages, 6758 KiB

Open AccessArticle

Effects of Oil Supply Condition on Spinning–Sliding EHL

by Wei Li, Xiaoling Liu, Qingen Meng, Mingming Ma, Tao Long and Feng Guo

Lubricants 2023, 11(10), 451; https://doi.org/10.3390/lubricants11100451 - 19 Oct 2023

Cited by 1 | Viewed by 1238

Abstract

An optical interference test rig with spinning elastohydrodynamic lubrication (EHL) was established to investigate the spinning lubrication performance under different oil-supply conditions. Variations in the shape and thickness of the film versus the velocity, the load, and the spinning factor under fully flooded [...] Read more.

An optical interference test rig with spinning elastohydrodynamic lubrication (EHL) was established to investigate the spinning lubrication performance under different oil-supply conditions. Variations in the shape and thickness of the film versus the velocity, the load, and the spinning factor under fully flooded lubrication were discussed, and the effects of the inlet-starvation position and oil-supply quantity were analyzed. The results show that the symmetry for the classical horseshoe shape does not exist under both spinning–rolling and spinning–sliding EHL conditions. Different from spinning–rolling, a dimple is generated more easily under the spinning–sliding condition. The dimple is related to the load and the speed. The effects of the inlet-starvation position on spinning EHL are different. When the inlet starvation is on the low-speed side of the contact, that is, proximal to the center of rotation, the inlet-starvation position extends from the proximal side to the center of rotation to the distal side to the center of rotation, i.e., the high-speed side of the contact, which is starved easily. When the starvation happens on the high-speed side, i.e., distal to the center of rotation, the starvation at this position becomes much more severe, and lubrication failure and a risk of wear will occur. In addition, the effects of oil-supply quantity on spinning EHL are important. Full article

(This article belongs to the Special Issue Friction and Wear of Rolling-Element Bearings)

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16 pages, 6321 KiB

Open AccessArticle

A General Approximate Solution for the Slightly Non-Axisymmetric Normal Contact Problem of Layered and Graded Elastic Materials

by Fabian Forsbach and Emanuel Willert

Lubricants 2023, 11(10), 450; https://doi.org/10.3390/lubricants11100450 - 18 Oct 2023

Cited by 1 | Viewed by 979

Abstract

We present a general approximate analytical solution for the normal contact of layered and functionally graded elastic materials for almost axisymmetric contact profiles. The solution only requires knowledge of the corresponding contact solution for indentation using a rigid cylindrical flat punch. It is [...] Read more.

We present a general approximate analytical solution for the normal contact of layered and functionally graded elastic materials for almost axisymmetric contact profiles. The solution only requires knowledge of the corresponding contact solution for indentation using a rigid cylindrical flat punch. It is based on the generalizations of Barber’s maximum normal force principle and Fabrikant’s approximation for the pressure distribution under an arbitrary flat punch in an inhomogeneous case. Executing an asymptotic procedure suggested recently for almost axisymmetric contacts of homogeneous elastic media results in a simple approximate solution to the inhomogeneous problem. The contact of elliptical paraboloids and indentation using a rigid pyramid with a square planform are considered in detail. For these problems, we compare our results to rigorous numerical solutions for a general (bonded or unbonded) single elastic layer based on the boundary element method. All comparisons show the quality and applicability of the suggested approximate solution. Based on our results, any compact axisymmetric or almost axisymmetric contact problem of layered or functionally graded elastic materials can be reduced asymptotically to the problem of indenting the material using a rigid cylindrical flat punch. The procedure can be used for different problems in tribology, e.g., within the framework of indentation testing or as a tool for the analysis of local features on a rough surface. Full article

(This article belongs to the Special Issue Advances in Contact Mechanics)

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26 pages, 19060 KiB

Open AccessArticle

The Influence of Scratches on the Tribological Performance of Friction Pairs Made of Different Materials under Water-Lubrication Conditions

by Qingchen Liang, Peng Liang, Feng Guo, Shuyi Li, Xiaohan Zhang and Fulin Jiang

Lubricants 2023, 11(10), 449; https://doi.org/10.3390/lubricants11100449 - 17 Oct 2023

Cited by 3 | Viewed by 1393

Abstract

Water-lubricated bearings are widely used in marine equipment, and the lubricating water often contains hard particles. Once these particles enter the gap between the bearing and the shaft, they can scratch the smooth surfaces of the shaft and bearing, influencing the working performance [...] Read more.

Water-lubricated bearings are widely used in marine equipment, and the lubricating water often contains hard particles. Once these particles enter the gap between the bearing and the shaft, they can scratch the smooth surfaces of the shaft and bearing, influencing the working performance of the bearing system. To investigate the effect of scratch parameters on tribological performance, this paper conducts multiple block-on-ring experiments and constructs a mixed-lubrication model under water-lubrication conditions. The results show that among the three commonly used bearing materials, the tribological performance of graphite block is the most sensitive to scratches on the test ring surface. Under the condition of one scratch (N = 1), the loading area of water film pressure is divided into two separate zones (a trapezoidal pressure zone and an extremely low-pressure zone). In addition, the variation of maximum water film pressure is determined by the positive effect (hydrodynamic pressure effect of fluid) and negative effect (“piercing effect” of the asperities). Compared with the scratch depth and scratch location, the scratch width has the most significant effect on the tribological performance of the block-on-ring system. The maximum contact pressure is located at both edges of the scratch due to the formation of a water sac structure. The scratch has a great influence on the transition of the lubrication state of the block-on-ring system. The existence of scratches increases the critical speed at which the lubrication state transits from mixed-lubrication to elastohydrodynamic lubrication, and the critical speed is directly proportional to the scratch width. Full article

(This article belongs to the Special Issue Water-Lubricated Bearings)

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0 pages, 6049 KiB

Open AccessArticle

High-Temperature Wear and Frictional Performance of Plasma-Nitrided AISI H13 Die Steel

by Ashish Kumar, Manpreet Kaur, Alphonsa Joseph, Ghanshyam Jhala, Tarun Nanda and Surinder Singh

Lubricants 2023, 11(10), 448; https://doi.org/10.3390/lubricants11100448 - 17 Oct 2023

Viewed by 1281

Abstract

Plasma nitriding, a surface treatment technique, is gaining popularity, as it is environment-friendly and offers superior mechanical properties. This research studied the wear and friction performance of AISI H13 die steel after plasma nitriding in a gas mixture of N2:H2 at 20:80, 50:50, [...] Read more.

Plasma nitriding, a surface treatment technique, is gaining popularity, as it is environment-friendly and offers superior mechanical properties. This research studied the wear and friction performance of AISI H13 die steel after plasma nitriding in a gas mixture of N2:H2 at 20:80, 50:50, and 80:20 (volume ratio) at a fixed time and temperature. This work aimed to analyze the sliding wear performance of the plasma-nitrided tool die steel in hot-forming operations at higher loads. Scanning electron microscopy/electron-dispersive spectroscopy (SEM/EDS) and X-ray diffraction (XRD) techniques were used to study the microstructures of the H13 die steel pins after plasma nitriding. Wear tests were performed on a high-temperature tribometer under uni-directional sliding and dry conditions using a high-temperature tribometer under a 50 N load at various operating temperatures ranging from 25 °C to 600 °C. The results show that the plasma-nitriding process with N₂:H₂ at 20:80 improved the wear behavior of H13 steel. The friction coefficients and wear volume losses for all the plasma-nitrided specimens were less than those of the untreated die steel. Full article

(This article belongs to the Special Issue Plasma Surface Treatments for Wear and Corrosion Protection)

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13 pages, 6056 KiB

Open AccessArticle

An Experimental Investigation on the Effects of the Base Fluid of External Fluid and Voltage on the Milling Performance of Nanofluid Composite Electrostatic Spraying

by Yu Su, Qingxiang Yang, Pan Liu and Jiaxi You

Lubricants 2023, 11(10), 447; https://doi.org/10.3390/lubricants11100447 - 16 Oct 2023

Viewed by 1341

Abstract

Nanofluid composite electrostatic spraying (NCES) is a new clean machining technology for minimum quantity lubrication. The base fluid of external fluid and voltage are the two important parameters that affect its performance. This study presented the effect of base fluid of external fluid [...] Read more.

Nanofluid composite electrostatic spraying (NCES) is a new clean machining technology for minimum quantity lubrication. The base fluid of external fluid and voltage are the two important parameters that affect its performance. This study presented the effect of base fluid of external fluid on milling force and temperature of NCES to determine the suitable base fluid and the best external/internal fluid. Herein, castor oil, castor oil-based nanofluid, sunflower oil, and sunflower oil-based nanofluid were employed as external fluid, and water and water-based nanofluid as internal fluid. Atomization experiments were conducted to determine the common voltage for different external/internal fluids to generate an applicable atomization mode. Under this voltage, morphology of applicable atomization mode, current and standard deviation, droplet speed, and electrowetting contact angle were explored to discuss the effect of base fluid on NCES milling. Next, the best external/internal fluid was used to further investigate the milling force and temperature under various voltages. Sunflower oil was the suitable base fluid for NCES, and sunflower oil-based nanofluid/water-based nanofluid was found to be the best external/internal fluid causing a significant reduction in force and temperature. Compared to castor oil, sunflower oil as the base fluid lowered the milling force and temperature by 5.4–10.8% and 6.3–7.9%, respectively. Within the voltage range of applicable atomization mode, raising the voltage lowered the milling force and temperature by 2.4% and 3.9%, respectively. Full article

(This article belongs to the Special Issue Methods of Application of Cutting Fluids in Machining)

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14 pages, 4044 KiB

Open AccessArticle

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

by Wei Li, Feng Guo, Chenglong Liu and Zhaoqun Ma

Lubricants 2023, 11(10), 446; https://doi.org/10.3390/lubricants11100446 - 16 Oct 2023

Cited by 1 | Viewed by 1319

Abstract

Using an optical elastohydrodynamic lubrication (EHL) test rig, oil film thickness and the coefficient of friction (COF) were measured, and the influence of stearic acid additive on the EHL performance of mineral oil 2137 was investigated. The results showed that 2137 with 0.3 [...] Read more.

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

(This article belongs to the Special Issue Friction and Wear of Rolling-Element Bearings)

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16 pages, 4836 KiB

Open AccessArticle

Research on Loaded Contact Analysis and Tooth Wear Calculation Method of Cycloid–Pin Gear Reducer

by Yongqiang Wang, Bingyang Wei, Zhen Wang, Jianjun Yang and Jiake Xu

Lubricants 2023, 11(10), 445; https://doi.org/10.3390/lubricants11100445 - 13 Oct 2023

Viewed by 1183

Abstract

This study establishes the geometric model of cycloid–pin gear meshing transmission based on the multi-tooth meshing characteristics of the cycloid speed reducer. The calculation and analysis of meshing motion parameters of the cycloid speed reducer are carried out. An integrated calculation flow is [...] Read more.

This study establishes the geometric model of cycloid–pin gear meshing transmission based on the multi-tooth meshing characteristics of the cycloid speed reducer. The calculation and analysis of meshing motion parameters of the cycloid speed reducer are carried out. An integrated calculation flow is presented for solving the question of the loaded tooth contact of the cycloid speed reducer by using the elimination clearance method of gradual contact and the quasi-Hertz contact simulation of the tooth surface under loads. The loaded transmission error is obtained, and both the number of pins participating in the meshing and the contact area of tooth surfaces are determined. Using the regression formula of the wear coefficient, the dynamic wear coefficient is quickly solved on the instantaneous contact line of the tooth surface. Thereby, the wear distribution law of two tooth surfaces appears. The results show that there is a singular point in the wear of the pin teeth, with a maximum wear of 100 μm, that seriously affects the meshing accuracy of the tooth surface and thus affects the accuracy and lifespan of the reducer. Full article

(This article belongs to the Special Issue Wear Mechanism Identification and State Prediction of Tribo-Parts)

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15 pages, 3786 KiB

Open AccessArticle

A Comparison of Hydrogen and Gasoline Piston Ring Simulations

by Stephen Richard Bewsher and Günter Offner

Lubricants 2023, 11(10), 444; https://doi.org/10.3390/lubricants11100444 - 13 Oct 2023

Viewed by 1423

Abstract

This paper presents a transient mixed-lubrication hydrodynamic and gas flow simulation model for a piston ring pack for a four-stroke internal combustion engine. The analyses carried out compare two fuel types, hydrogen and gasoline, at a 2000 rpm low engine load (20%), as [...] Read more.

This paper presents a transient mixed-lubrication hydrodynamic and gas flow simulation model for a piston ring pack for a four-stroke internal combustion engine. The analyses carried out compare two fuel types, hydrogen and gasoline, at a 2000 rpm low engine load (20%), as well as 3000 rpm low (20%) and high (100%) engine loads, to investigate the effects of the different fuels and loading conditions on the ring pack. In particular, the minimum oil film thickness at the top compression ring, the total ring friction of the ring pack, the friction power loss and the blow-by are studied. The simulation shows that, under the high load conditions at 3000 rpm, the hydrogen variant exhibits larger friction power losses, around a 200 W peak difference and larger blow-by throughout the expansion stroke of the engine cycle. A similar trend can be observed for the low loads, where larger friction power losses with peak differences of 30 W and 40 W for 2000 rpm and 3000 rpm, respectively, are observed. The blow-by results for the low load at 2000 rpm show a slight increase of approximately 22% more gas flow into the crankcase, while the 3000 rpm simulation shows a 50% increase in blow-by for the hydrogen variant at low load and a 40% increase at high load. The findings that are presented indicate that, although alternative fuel sources such as hydrogen are very attractive alternatives to fossil fuels such as gasoline, there can be unwanted side effects that could lead to the permanent damage of components through quicker wear or hydrogen embrittlement from the blow-by gas. Full article

(This article belongs to the Special Issue Tribology in Mobility, Volume II)

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14 pages, 7076 KiB

Open AccessArticle

Preparation and Tribological Behavior of Nitrogen-Doped Carbon Nanotube/Ag Nanocomposites as Lubricant Additives

by Shaokun Jia, Jiahuan Zhao, Guangzhen Hao, Jifeng Feng, Chuanbo Zhang, Zhihui Wang, Zhengfeng Jia and Yungang Bai

Lubricants 2023, 11(10), 443; https://doi.org/10.3390/lubricants11100443 - 13 Oct 2023

Viewed by 1012

Abstract

In this study, nitrogen-doped carbon nanotube/Ag nanocomposites (denoted as N-C/Ag) have been synthesized in a urea solution using a hydrothermal method. The carbon nanotubes, AgNO₃ solution, urea and poly-dopamine (PDA) served as carbon, silver, nitrogen and carbon sources, respectively. The results show [...] Read more.

In this study, nitrogen-doped carbon nanotube/Ag nanocomposites (denoted as N-C/Ag) have been synthesized in a urea solution using a hydrothermal method. The carbon nanotubes, AgNO₃ solution, urea and poly-dopamine (PDA) served as carbon, silver, nitrogen and carbon sources, respectively. The results show that the diameter of the carbon tubes was about 30 nm, and the Ag nanoparticles, with a diameter of ca. 10 nm, dispersed on the carbon tube surface. The Ag particle size decreased with a lower degree of crystallinity at a high temperature in the presence of urea. The friction and wear behavior of the oil acid (OA) modified N-C/Ag (OAN-C/Ag) as an additive in liquid paraffin (LP) were studied using a four-ball friction and wear tester. The results have shown that the coefficients of friction (COFs) and wear scar diameters (WSDs) of steel balls lubricated with LP-OAN-C/Ag decreased by 27.3% and 25.3%, respectively, relative to pure LP. Tribofilms containing Ag, carbon and nitride were formed on the worn steel ball surfaces. Details, the carbon, Fe₂O₃, azides and nitride, Ag and alloy and other compounds on the wear scars may improve tribological properties. The synergistic effect of carbon, Ag and urea plays a critical role during sliding. Full article

(This article belongs to the Special Issue Functional Lubricating Materials)

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23 pages, 8076 KiB

Open AccessArticle

Exploring the Impact of the Turning of AISI 4340 Steel on Tool Wear, Surface Roughness, Sound Intensity, and Power Consumption under Dry, MQL, and Nano-MQL Conditions

by Yusuf Fedai

Lubricants 2023, 11(10), 442; https://doi.org/10.3390/lubricants11100442 - 12 Oct 2023

Cited by 1 | Viewed by 1227

Abstract

Optimizing input parameters not only improves production efficiency and processing quality but also plays a crucial role in the development of green manufacturing engineering practices. The aim of the present study is to conduct a comparative evaluation of the cutting performance and machinability [...] Read more.

Optimizing input parameters not only improves production efficiency and processing quality but also plays a crucial role in the development of green manufacturing engineering practices. The aim of the present study is to conduct a comparative evaluation of the cutting performance and machinability process during the turning of AISI 4340 steel under different cooling conditions. The study analyzes cutting operations during turning using dry, minimum quantity lubrication, and nano- minimum quantity lubrication. As control parameters in the experiments, three different cooling types, cutting speeds (100, 150, 200 m/min), and feed rate (0.1, 0.15, 0.20 mm/rev) levels were applied. The experimental results show that the optimal output values are found to be Vb = 0.15 mm, Ra = 0.81µm, 88.1 dB for sound intensity and I = 4.18 A for current. Moreover, variance analysis was performed to determine the effects of input parameters on response values. Under dry, minimum quantity lubrication, and nano-minimum quantity lubrication processing conditions, parameters affecting tool wear, surface roughness, current by the motor shaft, and sound level were examined in detail, along with the chip morphology. The responses obtained were optimized according to the Taguchi S/N method. As a result of optimization, it was concluded that the optimum values for cutting conditions were nano-minimum quantity lubrication cooling and V = 100 m/min, f = 0.1 mm/rev cutting. Finally, it was observed that there was a 13% improvement in tool wear, 7% in current, 9% in surface roughness, and 8% in sound intensity compared to the standard conditions. In conclusion, it was determined that nano-minimum quantity lubrication with the lowest level of cutting and feed rate values provided the optimum results. Full article

(This article belongs to the Special Issue Methods of Application of Cutting Fluids in Machining)

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14 pages, 47483 KiB

Open AccessArticle

Measurement and Prediction of Sawing Characteristics Using Dental Reciprocating Saws: A Pilot Study on Fresh Bovine Scapula

by Dedong Yu, Fan Zou, Wenran Zhang, Qinglong An and Ping Nie

Lubricants 2023, 11(10), 441; https://doi.org/10.3390/lubricants11100441 - 12 Oct 2023

Viewed by 952

Abstract

Bone sawing is one of the most common operations during traditional dental and cranio-maxillofacial surgery and training systems based on virtual reality technology. It is necessary to predict and update conditions (including the sawing force, temperature and tool wear) in real time during [...] Read more.

Bone sawing is one of the most common operations during traditional dental and cranio-maxillofacial surgery and training systems based on virtual reality technology. It is necessary to predict and update conditions (including the sawing force, temperature and tool wear) in real time during VR surgical training and surgical simulation. All the specimens used in this study were fresh bovine scapula. The forces and temperatures were measured during the sawing process. Additionally, the thermal conductivity was measured via a laser flash instrument. Response surface methodology (RSM) was adopted to analyze and model the sawing force and sawing temperature. Meanwhile, tool wear was observed using a scanning electron microscope. The regression models of the sawing force and temperature rise under different experimental conditions were acquired. To obtain the minimum force within the recommended parameter ranges of commonly used medical reference parameters for bone sawing, a higher rotational speed combined with a lower feed rate were recommended. When considering the sawing force and temperature rise comprehensively, the rotational speed should not be extremely high (about 13,000 rpm is recommended). Meanwhile, abrasive wear is the main wear mode of saw blades. In order to avoid surgery failure, it is necessary to replace the saw blade in time. The experimental data were confirmed to be scientific and accurate for the predicted models of sawing conditions. To minimize the main cutting force, a feed rate of 40 mm/min combined with a rotational speed of 13,700 rpm is recommended. High cutting temperatures have the potential to cause irreversible tissue damage, so surgeons using dental reciprocating saws need to avoid excessively high-speed gears. Full article

(This article belongs to the Special Issue Friction and Wear of Cutting Tools and Cutting Tool Materials)

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12 pages, 2781 KiB

Open AccessArticle

The Standard for Assessing Water Resistance Properties of Lubricating Grease Using Contact Angle Measurements

by Koottaparambil Lijesh, Roger A. Miller, Raj Shah, Khosro Shirvani and Michael M. Khonsari

Lubricants 2023, 11(10), 440; https://doi.org/10.3390/lubricants11100440 - 12 Oct 2023

Cited by 1 | Viewed by 1655

Abstract

Many grease-lubricated machines operate in wet environments, and are vulnerable to contamination because of water exposure. Reports suggest that even the presence of 1% water in grease reduces the life of a bearing by 90%. Nevertheless, only a few qualitative tests and standards [...] Read more.

Many grease-lubricated machines operate in wet environments, and are vulnerable to contamination because of water exposure. Reports suggest that even the presence of 1% water in grease reduces the life of a bearing by 90%. Nevertheless, only a few qualitative tests and standards are available to characterize the water resistance properties of greases. In this paper, we propose a standard for evaluating the water resistance properties of greases by studying their hydrophobic and hydrophilic nature via a custom-designed apparatus for measuring the grease contact angle. In this approach, a water droplet is dispensed onto the surface of the grease and the contact angle of the droplet is studied. For this purpose, an apparatus was designed, built, and tested with twelve different greases. To validate the efficacy of the test method and setup, tests were performed at two different locations by independent operators. From the obtained contact angle values, the authors propose categorizing a grease’s water-resistance properties into five different grades that can be set as guidelines for the industrial user when selecting a grease for machinery operation in a wet environment. The classification of the water-repellent properties of greases, using the proposed standard is compared with existing ASTM standards used for evaluation of grease properties in the presence of water. Full article

(This article belongs to the Special Issue Grease II)

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13 pages, 5008 KiB

Open AccessArticle

Research on Wear of Micro-Textured Tools in Turning GH4169 during Spray Cooling

by Jingshu Hu, Jiaxuan Wei, Xinmin Feng and Zhiwei Liu

Lubricants 2023, 11(10), 439; https://doi.org/10.3390/lubricants11100439 - 12 Oct 2023

Viewed by 1017

Abstract

In this study, the wear resistance of micro-textured tools was explored. Micro-textured tools with different morphologies were used in turning GH4169 during spray cooling. The tool wear on the rake face of the different micro-texture morphologies was investigated through simulation and experiments. Firstly, [...] Read more.

In this study, the wear resistance of micro-textured tools was explored. Micro-textured tools with different morphologies were used in turning GH4169 during spray cooling. The tool wear on the rake face of the different micro-texture morphologies was investigated through simulation and experiments. Firstly, based on the existing research on bionics, micro-textures with five different morphologies were designed on the rake face of carbide tools. A simulation model of cutting GH4169 during spray cooling was established, and the tools with designed micro-textures were used in it. The influence of the different micro-texture morphologies on the tool wear was analyzed. Secondly, the designed micro-textured tools with five different morphologies were produced using a femtosecond laser. Cutting experiments were conducted using the micro-textured tools during spray cooling. The wear area of the rake face was measured based on the infinitesimal method, and the optimal morphology with the best anti-wear ability was obtained. This study provides technical support for the design and development of micro-textured tools with an improved cutting performance, and contribute to the promotion and application of micro-textured tools. Full article

(This article belongs to the Special Issue Friction and Wear of Cutting Tools and Cutting Tool Materials)

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15 pages, 6509 KiB

Open AccessArticle

Investigation of the Material Elasto-Plastic Response under Contact Indentation: The Effect of Indenter Material

by Davide Tonazzi, Francesco Piva, Alexandre Mondelin, Gwenolè Le Jeune, Yves Mahéo and Francesco Massi

Lubricants 2023, 11(10), 438; https://doi.org/10.3390/lubricants11100438 - 11 Oct 2023

Viewed by 1417

Abstract

When dealing with joints and bearings, high pressures localised at the contact interface lead to residual plastic strain. The present paper combines numerical simulations and experimental tests to investigate the role of the material constitutive law in the indentation process. Numerical indentation tests [...] Read more.

When dealing with joints and bearings, high pressures localised at the contact interface lead to residual plastic strain. The present paper combines numerical simulations and experimental tests to investigate the role of the material constitutive law in the indentation process. Numerical indentation tests between similar materials showed a good agreement with the experiments when classical material laws recovered from tensile-compressive tests on bulk samples were accounted for. On the other hand, when simulating indentation between different materials in contact, the comparison between the numerical and experimental results highlighted the limits of using classical material laws. Bilinear material laws were then derived for different steel materials (ASP 2060 PM, 100Cr6, 440C, Marval X12, and Z15 CN17-03) in contact with a ceramic indenter, leading to the correct simulation of the residual indentation profiles (error less than 5%). The proposed approach to determine suitable material laws for indentation between dissimilar materials can be further applied when dealing with applications involving contacts undergoing local plastic deformation. Full article

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14 pages, 4017 KiB

Open AccessArticle

Influence of Dry-Film Lubricants on Bond Strength and Corrosion Behaviour of 6xxx Aluminium Alloy Adhesive Joints for the Automotive Industry

by Ralph Gruber, Tanja Denise Singewald, Thomas Maximilian Bruckner, Laura Hader-Kregl, Martina Hafner and David Stifter

Lubricants 2023, 11(10), 437; https://doi.org/10.3390/lubricants11100437 - 11 Oct 2023

Viewed by 1271

Abstract

In the automotive industry, the application of dry lubricants on aluminium is indispensable for achieving a high-quality forming behaviour. To provide a short production time, these forming aids are not removed during the joining step. The aim of this study is the characterisation [...] Read more.

In the automotive industry, the application of dry lubricants on aluminium is indispensable for achieving a high-quality forming behaviour. To provide a short production time, these forming aids are not removed during the joining step. The aim of this study is the characterisation of the influence of dry lubricants on the bond strength and the corrosion resistance of a 6xxx aluminium alloy for automotive applications. For this purpose, samples with a well-defined surface were coated with 1 g/m² dry lubricant and joined with a commercial thermosetting 1K epoxy structural adhesive. The bond strength was measured with lap shear tests. To evaluate the corrosion resistance of the adhered aluminium samples, an immersion test in a 5 wt.% NaCl solution was used. Based on the fracture pattern analysis, the corrosion behaviour could be described, and the possible corrosion mechanisms are proposed. The influence of the load quantity of the dry lubricants is observed microscopically and mechanically. The environmentally induced degradation process of the adhesive is examined by an investigation of the volumetric change during the testing and with scanning electron microscopy. Using a simulation, the changes in the adhesive polymer matrix at the metal–adhesive interface caused by the dry lubricants are examined using polymer test procedures like dynamic mechanical analysis, differential scanning calorimetry and tensile tests. The results show a significant effect of the forming aid on the corrosion resistance of the adhered aluminium samples against the corrosive infiltration of the metal–adhesive interface. Full article

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21 pages, 6435 KiB

Open AccessArticle

Change in Time of the Value of Dry and Lubricated Friction Coefficients for Surfaces Generated by Different Processing Methods

by Gheorghe Nagîț, Andrei Marius Mihalache, Oana Dodun, Adelina Hrițuc, Laurențiu Slătineanu and Vasile Merticaru

Lubricants 2023, 11(10), 436; https://doi.org/10.3390/lubricants11100436 - 09 Oct 2023

Viewed by 1025

Abstract

The surfaces of the mechanical parts involved in friction processes are made using different processing methods. Each of these processing methods leads to a certain profile of the asperities of the generated surfaces. When such surfaces are subjected to friction processes, it is [...] Read more.

The surfaces of the mechanical parts involved in friction processes are made using different processing methods. Each of these processing methods leads to a certain profile of the asperities of the generated surfaces. When such surfaces are subjected to friction processes, it is possible to produce a change in time in the magnitude of the friction coefficient. For experimental research, the outer cylindrical surfaces of some steel test samples were generated using various machining methods such as turning, grinding, ball and diamond burnishing, and vibroburnishing. Later, using a device adapted to a lathe, experimental tests were carried out following the time variation of the value of the friction coefficient under conditions of dry friction and lubricated friction, respectively. The results of the experimental tests were processed mathematically, being determined by empirical mathematical models that highlight the influence of the final processing methods of the surface, the presence of the lubricant, and the test duration on the variation of the friction coefficient. It was found that first, there is an increase over time in the values of the friction coefficient, and then the values of this coefficient stabilize at certain values. The increase in the coefficient of friction until reaching the stabilization value takes place in a proportion of approximately 148–305%. Full article

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14 pages, 7280 KiB

Open AccessArticle

Simulation Study on the Influence of a Laser Power Change on the Residual Stress of a Laser-Melting RuT300 Valve Seat

by Wendan Tan and Ming Pang

Lubricants 2023, 11(10), 435; https://doi.org/10.3390/lubricants11100435 - 09 Oct 2023

Viewed by 942

Abstract

In order to effectively suppress the cracking induced by the excessive residual stress of a laser-melting RuT300 valve seat, the influence of a laser power change on the residual stress was studied by constructing a finite element simulation model of a new power [...] Read more.

In order to effectively suppress the cracking induced by the excessive residual stress of a laser-melting RuT300 valve seat, the influence of a laser power change on the residual stress was studied by constructing a finite element simulation model of a new power valve seat. The absorption rate of the laser energy on the surface of the material and the change in thermophysical parameters with temperature were taken into account in the model. The results show that the melting and phase-change-hardening areas can be obtained by the laser-melting process. With the increase in laser power, the peak temperature of the molten pool increased almost linearly. The melting zone area and the phase-change-hardening zone depth increased. When the laser power was increased from 2000 to 2600 W, the peak temperature of the laser-melting RuT300 valve seat increased from 2005.09 to 2641.93 °C, the maximum depth of the melting area increased from 0.55 to 0.86 mm, the maximum width of the melting area increased from 3.42 to 4.21 mm, and the maximum depth of the phase-change-hardening area increased from 0.55 to 0.64 mm. The circumferential residual tensile stress in the melting area was much higher than in the radial and axial directions. Along the laser scanning direction, the residual stress in the melting area increased as a whole, and the residual stress in the laser-scanning finishing area greatly increased. With the increase in laser power, the circumferential residual stress at the previous scanning moment decreased, and at the closing moment of the scan, the circumferential residual stress increased with the increase in laser power. Full article

(This article belongs to the Special Issue Recent Advances in High Temperature Tribology)

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15 pages, 14704 KiB

Open AccessArticle

Friction and Wear Characteristics of Fe₃O₄ Nano-Additive Lubricant in Micro-Rolling

by Yuchuan Zhu, Hongmei Zhang, Na Li and Zhengyi Jiang

Lubricants 2023, 11(10), 434; https://doi.org/10.3390/lubricants11100434 - 08 Oct 2023

Cited by 2 | Viewed by 1172

Abstract

As nanotechnology has developed, some nano-additives have been employed to improve the performance of lubricants. The mechanisms of nano-additives still need to be investigated. The wear characteristics of Fe₃O₄ nano-additive lubricant were investigated in this study. Different diameters of Fe [...] Read more.

As nanotechnology has developed, some nano-additives have been employed to improve the performance of lubricants. The mechanisms of nano-additives still need to be investigated. The wear characteristics of Fe₃O₄ nano-additive lubricant were investigated in this study. Different diameters of Fe₃O₄ nanoparticles were mixed in basic oil using an ultrasonic mixer. The new lubricant was used for analytical tests at room temperature. The results showed that nano-lubricants with 20 nm nanoparticles increase the oil film strength. The coefficient of friction was reduced when 20 nm diameter 8 wt% Fe₃O₄ nanoparticles were mixed with lubricants. The effect of surfactants and nanoparticles in the base oil was measured using numerical simulation methods. The adsorption capacity of the lubricants was significantly improved by Fe₃O₄ nanoparticles, particularly when looking at the small relative atomic mass of the metal. The 8 wt% Fe₃O₄ lubricant exhibited optimal tribological properties when applied in micro-rolling tests. The results showed that the surface quality of the rolled samples was significantly improved, and the rolling force was dramatically reduced. At the same time, the shapes of the samples were effectively controlled in the rolling process. Therefore, Fe₃O₄ nanoparticles can improve the friction and wear characteristics of lubricants. Full article

(This article belongs to the Special Issue Progress and Challenges in Lubrication: Green Tribology)

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16 pages, 8312 KiB

Open AccessArticle

Tribological Performance of Steel/W-DLC and W-DLC/W-DLC in a Solid–Liquid Lubrication System Additivated with Ultrathin MoS₂ Nanosheets

by Meirong Yi, Taoping Wang, Zizheng Liu, Jin Lei, Jiaxun Qiu and Wenhu Xu

Lubricants 2023, 11(10), 433; https://doi.org/10.3390/lubricants11100433 - 07 Oct 2023

Cited by 1 | Viewed by 961

Abstract

In this paper, MoS₂ nanosheets with an ultrathin structure were fabricated using a solvothermal method and further added into PAO oil, which was further combined with W-DLC coating to constitute a solid–liquid lubricating state. The influences of MoS₂ concentration, applied load [...] Read more.

In this paper, MoS₂ nanosheets with an ultrathin structure were fabricated using a solvothermal method and further added into PAO oil, which was further combined with W-DLC coating to constitute a solid–liquid lubricating state. The influences of MoS₂ concentration, applied load and counter surfaces on the lubricating of the solid–liquid hybrid lubricating system were explored through a ball-on-disk tribometer. The friction results indicated that the steel/W-DLC and W-DLC/W-DLC tribopairs lubricated with ultrathin MoS₂ possessed better friction reduction and wear resistance behaviors in comparison to pure PAO oil. However, compared to the steel/steel couple case, the prepared MoS₂ nanosheets exhibited a more efficient lubricating effect for the W-DLC/W-DLC couple. The beneficial boundary lubricating impact of MoS₂ nanosheets on self-mated W-DLC coated rubbing surfaces could be attributed to the tribochemical reaction between MoS₂ and doping W element in DLC, resulting in a formation of a thin tribofilm at both counterparts. Meanwhile, the extent of graphitization of W-DLC film induced by friction was alleviated because of the lubrication and protection from the formation of MoS₂-based tribofilm at both counterparts. Full article

(This article belongs to the Special Issue Functional Lubricating Materials)

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12 pages, 14397 KiB

Open AccessArticle

Effect of Argon Flow Rate on Tribological Properties of Rare Earth Ce Doped MoS₂ Based Composite Coatings by Magnetron Sputtering

by Changling Tian, Haichao Cai, Yujun Xue, Lulu Pei and Yongjian Yu

Lubricants 2023, 11(10), 432; https://doi.org/10.3390/lubricants11100432 - 07 Oct 2023

Cited by 1 | Viewed by 1040

Abstract

Exploring the doping components of the coating is of great significance for improving the tribological properties of the MoS₂-based coating. The optimization of magnetron sputtering process parameters can also improve the coating quality. In this paper, the effects of working gas [...] Read more.

Exploring the doping components of the coating is of great significance for improving the tribological properties of the MoS₂-based coating. The optimization of magnetron sputtering process parameters can also improve the coating quality. In this paper, the effects of working gas flow rate on the microstructure in a vacuum chamber, nano-hardness, and tribological properties of Ce-Ti/MoS₂ coatings were studied using DC and RF unbalanced co-sputtering technology. It is found that the coating structure was coarse and porous when the Ar flow rate was excessive (70 sccm), significantly affecting the mechanical properties; there are pit defects on the surface of the coating when the flow rate is just minor (30 sccm), and the coating easily falls off during the friction process. When the flow rate is 40~60 sccm, the coating grows uniformly, the hardness reaches 7.85 GPa at 50 sccm, and the wear rate is only 4.42 × 10⁻⁷ mm³ N⁻¹ m⁻¹ at 60 sccm. The coating doped with Ce and Ti is an approximate amorphous structure. Under appropriate gas flow rate conditions, the friction induces a transfer film with a layered structure, and the MoS₂ (002) crystal plane orientation is arranged in parallel at the edge of the wear debris, effectively reducing the shear force during sliding and reducing wear. Based on rare earth doping, this study improves the tribological properties by optimizing the working gas parameters, which plays a reference role in preparing high-quality MoS₂-based coatings. Full article

(This article belongs to the Special Issue Tribology of 2D Nanomaterials)

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21 pages, 11116 KiB

Open AccessArticle

An AI-Extended Prediction of Erosion-Corrosion Degradation of API 5L X65 Steel

by Ariel Espinoza-Jara, Igor Wilk, Javiera Aguirre and Magdalena Walczak

Lubricants 2023, 11(10), 431; https://doi.org/10.3390/lubricants11100431 - 05 Oct 2023

Viewed by 1059

Abstract

The application of Artificial Neuronal Networks (ANN) offers better statistical accuracy in erosion-corrosion (E-C) predictions compared to the conventional linear regression based on Multifactorial Analysis (MFA). However, the limitations of ANN to require large training datasets and a high number of inputs pose [...] Read more.

The application of Artificial Neuronal Networks (ANN) offers better statistical accuracy in erosion-corrosion (E-C) predictions compared to the conventional linear regression based on Multifactorial Analysis (MFA). However, the limitations of ANN to require large training datasets and a high number of inputs pose a practical challenge in the field of E-C due to the scarcity of data. To address this challenge, a novel ANN method is proposed, structured to a small training dataset and trained with the aid of synthetic data to produce an E-C neural network (E-C NN), applied for the first time in the study of E-C wear synergy. In the process, transfer learning is applied by pre-training and fine-tuning the model. The initial dataset is created from experimental data produced in a slurry pot setup, exposing API 5L X65 steel to a turbulent copper tailing slurry. To the previously known E-C scenario for selected values of flow velocity, particle concentration, temperature, pH, and the content of the dissolved

C u^{2 +}

, new experimental data of stand-alone erosion and stand-alone corrosion is added. The prediction of wear loss by E-C NN considers individual parameters and their interactions. The main result is that E-C ANN provides better prediction than MFA as evaluated by a mean squared error (MSE) values of 2.5 and 3.7, respectively. The results are discussed in the context of the cross-effect between the proposed prediction model and the resulting estimation of relative contribution to E-C synergy, which is better predicted by the E-C NN. The E-C NN model is concluded to be a viable alternative to MFA, delivering similar prediction with better sensitivity to E-C synergy at shorter computation times when using the same experimental dataset. Full article

(This article belongs to the Special Issue Recent Advances in Machine Learning in Tribology)

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18 pages, 5009 KiB

Open AccessArticle

Tribological Behavior Characterization and Fault Detection of Mechanical Seals Based on Face Vibration Acceleration Measurements

by Qingfeng Wang, Yunfeng Song, Hua Li, Yue Shu and Yang Xiao

Lubricants 2023, 11(10), 430; https://doi.org/10.3390/lubricants11100430 - 05 Oct 2023

Cited by 1 | Viewed by 1051

Abstract

A mechanical seal is a common type of rotating shaft seal in rotating machinery and plays a key role in the fluid seal of rotating machinery, such as centrifugal pumps and compressors. Given the performance degradation caused by the wear to the face [...] Read more.

A mechanical seal is a common type of rotating shaft seal in rotating machinery and plays a key role in the fluid seal of rotating machinery, such as centrifugal pumps and compressors. Given the performance degradation caused by the wear to the face of the contact mechanical seal during operation and the lack of effective predictive maintenance monitoring methods and evaluation indexes, a method for measuring the acceleration of the mechanical seal face’s vibration was pro-posed. The influence of face performance degradation and rotational speed change on the tribo-logical regime of the mechanical seal was investigated. The proposed fault detection model based on support vector data description (SVDD) was constructed. A mechanical seal face degradation test rig verifies the usability of the proposed method. The results show that in the mixed lubrication (ML) regime, the vibration sensitivity of the face increases with the increase in rotational speed. With the decrease in the face performance, the vibration-sensitive characteristic parameters of the face in-crease and change from the ML regime to the boundary lubrication (BL) regime. The incipient fault detection model can warn about incipient faults of mechanical seals. Here, the axial detection result predicted that maintenance would be required 10.5 months earlier than the actual failure time, and the radial and axial detection results predicted required maintenance 12 months earlier than the actual failure. Full article

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27 pages, 18120 KiB

Open AccessArticle

Research on the Service Condition Monitoring Method of Rolling Bearings Based on Isomorphic Data Fusion

by Yanfei Zhang, Yang Liu, Mingqi Yang, Xiaoyang Feng, Qianxiang Zhu and Lingfei Kong

Lubricants 2023, 11(10), 429; https://doi.org/10.3390/lubricants11100429 - 04 Oct 2023

Cited by 1 | Viewed by 865

Abstract

In order to solve the problem that it is difficult for a single sensor to accurately characterize the running state of rotating bearings under complex working conditions, this paper proposes a data-level fusion method based on multi-source isomorphic sensors to monitor spindle bearings. [...] Read more.

In order to solve the problem that it is difficult for a single sensor to accurately characterize the running state of rotating bearings under complex working conditions, this paper proposes a data-level fusion method based on multi-source isomorphic sensors to monitor spindle bearings. First, new vibration signals in the X,Y,Z direction were obtained through the process of decomposing, de-noise, and reconstructing. Second, the PCA algorithm was used to select the time-domain and frequency-domain features of the vibration signals, construct the feature matrix, and perform dimensionality reduction in the feature matrix. Finally, the entropy weight method was introduced to obtain the initial weights of the three directions as the inputs of the adaptive function. The chaotic particle swarm optimization algorithm proposed in this paper helps particles jump out of the local optimum. Chaotic mapping is used to initialize the velocity and position of the particles, which calculates globally optimal weights in three directions. In order to extract bearing signal features more accurately and efficiently, a DenseNet and Transformer (DAT) feature extraction model is proposed to deal with the complex changes and noise interference of bearing signals. Through the open data set of Jiangnan University and the data collected by our own experimental platform, the maximum accuracy of the DAT model was verified to be 100%. Full article

(This article belongs to the Special Issue Advances in Bearing Lubrication and Thermodynamics 2023)

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16 pages, 10380 KiB

Open AccessArticle

A Contribution to Experimental Identification of Frequency-Dependent Dynamic Coefficients of Tilting-Pad Journal Bearings with Centered and Off-Centered Pivot

by Philipp Zemella, Daniel Vetter, Thomas Hagemann and Hubert Schwarze

Lubricants 2023, 11(10), 428; https://doi.org/10.3390/lubricants11100428 - 03 Oct 2023

Viewed by 942

Abstract

Linearized dynamic bearing parameters and models are of essential interest for rotordynamic analyses in machine design. This paper experimentally studies the impact of pad preload and pivot offset on the frequency-dependent characteristics of dynamic stiffness (K) and damping coefficients (C) of a KC-model [...] Read more.

Linearized dynamic bearing parameters and models are of essential interest for rotordynamic analyses in machine design. This paper experimentally studies the impact of pad preload and pivot offset on the frequency-dependent characteristics of dynamic stiffness (K) and damping coefficients (C) of a KC-model for tilting-pad journal bearings. For this purpose, two four-pad test bearing configurations (preload

m = 0.17

, pivot offset 0.5 and preload

m = 0.47

, pivot offset 0.6) that differ highly with respect to the pad design parameters are investigated. Contributing effects on the results due to geometric differences are excluded as far as possible, as only one aligning ring and one pivot support design is used. The tests are conducted on a high-performance test rig for surface speeds up to 140 m/s and excitation frequencies of 500 Hz. Significant deviations between the two bearings are identified that generally match theoretically predicted differences and, therefore, contribute to the validation of dynamic bearing modeling. Full article

(This article belongs to the Special Issue Condition Monitoring and Simulation Analysis of Bearings)

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16 pages, 4691 KiB

Open AccessArticle

Characterisation of the Contact between Cross-Country Skis and Snow: On the Multi-Scale Interaction between Ski Geometry and Ski-Base Texture

by Kalle Kalliorinne, Gustav Hindér, Joakim Sandberg, Roland Larsson, Hans-Christer Holmberg and Andreas Almqvist

Lubricants 2023, 11(10), 427; https://doi.org/10.3390/lubricants11100427 - 03 Oct 2023

Cited by 1 | Viewed by 2125

Abstract

In elite endurance sports, marginal differences in finishing times drive ongoing equipment improvement to enhance athlete performance. In cross-country skiing, researchers, since the 1930s, have faced the challenge of minimising the resistance caused by friction in the contact between skis and snow. This [...] Read more.

In elite endurance sports, marginal differences in finishing times drive ongoing equipment improvement to enhance athlete performance. In cross-country skiing, researchers, since the 1930s, have faced the challenge of minimising the resistance caused by friction in the contact between skis and snow. This study was designed to evaluate the multi-scale interaction between the macro-scale ski-camber profile and the micro-scale ski-base texture. Considerations included real contact area, average interfacial separation, and total reciprocal interfacial separation between the ski and snow, which are properties that are intimately coupled to ski–snow friction. We found that both the profile of the ski camber and the texture of the ski base play decisive roles in determining viscous friction. At the same time, the texture of the ski base exerts a greater impact on the average real contact pressure, real contact area, and minimal average interfacial separation between the ski and snow than the ski-camber profile. Full article

(This article belongs to the Special Issue Multiscale and Modern Solutions in the Simulation of Lubricated Contacts)

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14 pages, 51762 KiB

Open AccessArticle

Analysis of the Effect of the Chemical Composition of Bearing Alloys on Their Wear under Wet Friction Conditions

by Marcin Madej and Beata Leszczyńska-Madej

Lubricants 2023, 11(10), 426; https://doi.org/10.3390/lubricants11100426 - 02 Oct 2023

Viewed by 982

Abstract

This paper discusses the results of a study to determine the effect of the chemical composition of two tin-based bearing alloys (B89 and B83) on their tribological properties. The tribological properties were tested using a T05 block-on-ring tester under technically dry and wet [...] Read more.

This paper discusses the results of a study to determine the effect of the chemical composition of two tin-based bearing alloys (B89 and B83) on their tribological properties. The tribological properties were tested using a T05 block-on-ring tester under technically dry and wet friction conditions. The research includes the determination of the wear rates, loss of mass, coefficients of friction, and changes in the coefficient of friction as a function of the process and material parameters. A study of the microstructure and base properties of such alloys, which affect the tribological properties and wear, are also presented. The study showed that chemical composition has a significant effect on the tribological properties; increasing the proportion and changing the morphology of the SnSb precipitates to rhomboidal in the B83 alloy results in an increase in wear resistance represented by loss of mass. Decreasing the size and proportion of these precipitates results in a stabilization of the frictional force variation and a slight decrease in the coefficient of friction. The research showed that SnSb phase precipitation is mainly responsible for the wear resistance of the investigated bearing alloys. Full article

(This article belongs to the Special Issue Tribological Properties and Failure Prediction in Mechanical Elements)

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