Tribology: Latest Advances and Prospects

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Applied Sciences applsci	2.5	5.3	2011	17.8 Days	CHF 2400
Vibration vibration	1.9	3.2	2018	22 Days	CHF 1600
Lubricants lubricants	3.1	3.6	2013	16.7 Days	CHF 2600

13 pages, 1605 KiB

Open AccessArticle

Identification by GC-MS Analysis of Organics in Manufactured Articles through a D-Optimal Design

by Monica Romagnoli, Valeria Polliotto, Eugenio Alladio and Marco Pazzi

Appl. Sci. 2022, 12(14), 7320; https://doi.org/10.3390/app12147320 - 21 Jul 2022

Cited by 1 | Viewed by 1587

Many manufactured articles are made of composite materials often bonded by a phenolic resin. Through a D-optimal design, we optimized a method to characterize phenolic resins after the extraction process by GC-MS analysis. The study was conducted on three different phenolic resins and [...] Read more.

Many manufactured articles are made of composite materials often bonded by a phenolic resin. Through a D-optimal design, we optimized a method to characterize phenolic resins after the extraction process by GC-MS analysis. The study was conducted on three different phenolic resins and four manufactured articles with the same inorganic composition and different analyzed binders. Moreover, three cardanol resins that differ in their production systems were analyzed to see if there were differences between them. Through Soxhlet extraction with dichloromethane or acetone, it is possible to differentiate the raw materials through characteristic compounds and to identify them in the manufactured articles. Full article

(This article belongs to the Topic Tribology: Latest Advances and Prospects)

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19 pages, 6366 KiB

Open AccessArticle

Automatic Transmission Fluids in Electrified Transmissions: Compatibility with Elastomers

by Alejandro García-Tuero, Beatriz Ramajo, Guillermo D. Valbuena, Alfonso Fernández-González, Rafael Mendoza, Alberto García and Antolin Hernández Battez

Appl. Sci. 2022, 12(12), 6213; https://doi.org/10.3390/app12126213 - 18 Jun 2022

Viewed by 2190

Abstract

The location of the electric motor (EM) inside the transmission in an electric vehicle requires the compatibility of the automatic transmission fluids (ATFs) with the materials of the EM and the transmission. This work studies the compatibility of four conventional ATFs with three [...] Read more.

The location of the electric motor (EM) inside the transmission in an electric vehicle requires the compatibility of the automatic transmission fluids (ATFs) with the materials of the EM and the transmission. This work studies the compatibility of four conventional ATFs with three elastomers: fluoroelastomer (FKM), ethylene-propylene-diene monomer (EPDM), and vinyl-methyl silicone rubber (silicone). Changes in volume, hardness, tensile strength, and elongation at break of the elastomers after aging in the ATFs were measured, and additional Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric and derivative thermogravimetric (TGA and DTGA) tests were performed. The four ATFs showed high or medium compatibility with FKM and silicone, and low compatibility with EPDM. This low compatibility was related to changes in the composition and crystalline structure of the elastomer. The non-compatibility of the EPDM with the oils from Group III was also proven. Full article

(This article belongs to the Topic Tribology: Latest Advances and Prospects)

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17 pages, 8989 KiB

Open AccessArticle

Thermal Effects in Slender EHL Contacts

by Marko Tošić, Roland Larsson and Thomas Lohner

Lubricants 2022, 10(5), 89; https://doi.org/10.3390/lubricants10050089 - 6 May 2022

Cited by 8 | Viewed by 3470

Abstract

This study deals with experimental and numerical analysis of the thermal effects of slender elastohydrodynamically lubricated (EHL) contacts under high sliding. Thereby, the entrainment direction is along the major axis of the contact ellipse. Film thickness measurements were carried out on an optical [...] Read more.

This study deals with experimental and numerical analysis of the thermal effects of slender elastohydrodynamically lubricated (EHL) contacts under high sliding. Thereby, the entrainment direction is along the major axis of the contact ellipse. Film thickness measurements were carried out on an optical EHL tribometer with a glass disk and steel roller. Numerical EHL solutions were obtained with consideration for non-Newtonian rheology and thermal effects. The results show that thermal effects can result in a strong viscosity wedge diverting oil flow to the contact sides. For high positive sliding, in which the glass disk moves faster, the influence of entrainment speed on minimum film thickness is almost negligible, while the film thickness shows a continuous decrease in gap length direction. Full article

(This article belongs to the Topic Tribology: Latest Advances and Prospects)

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13 pages, 2182 KiB

Open AccessArticle

Compatibility of Automatic Transmission Fluids with Structural Polymers Used in Electrified Transmissions

by Alberto García, Guillermo D. Valbuena, Alejandro García-Tuero, Alfonso Fernández-González, José L. Viesca and Antolin Hernández Battez

Appl. Sci. 2022, 12(7), 3608; https://doi.org/10.3390/app12073608 - 1 Apr 2022

Cited by 8 | Viewed by 2848

Abstract

The use of the electric motor (EM) inside the transmission in electric vehicles (EVs) requires compatibility between the automatic transmission fluids (ATFs) and the materials of the EM and the transmission. The goal of this work is to study the compatibility of four [...] Read more.

The use of the electric motor (EM) inside the transmission in electric vehicles (EVs) requires compatibility between the automatic transmission fluids (ATFs) and the materials of the EM and the transmission. The goal of this work is to study the compatibility of four conventional ATFs with three structural polymers (PEEK, PTFE, and PA66) and the feasibility of using them in EVs with the EM located inside the transmission. Changes in volume, hardness, tensile strength, and elongation at break were determined in the polymers after ageing in the ATFs. The polymers were aged in each ATF at 100 °C for periods of time of 168, 336, 504, and 672 h. Complementary tests such as XRD, FT-IR, and DSC were performed to explain the changes found in the measured mechanical properties. PEEK and PTFE showed very low variations in their mechanical properties, while PA66 showed significant changes in elongation at break. The XRD, FT-IR, and DSC tests revealed a change in the crystalline structure of PEEK and PA66. The FT-IR results showed that the polymers were affected more by the time of ageing than by the type of ATF. All of the ATFs showed high compatibility with PEEK and PTFE, and medium compatibility with PA66. Full article

(This article belongs to the Topic Tribology: Latest Advances and Prospects)

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16 pages, 2821 KiB

Open AccessTechnical Note

The Investigation of Viscometric Properties of the Most Reputable Types of Viscosity Index Improvers in Different Lubricant Base Oils: API Groups I, II, and III

by Seyed Ali Khalafvandi, Muhammad Ali Pazokian and Ehsan Fathollahi

Lubricants 2022, 10(1), 6; https://doi.org/10.3390/lubricants10010006 - 3 Jan 2022

Cited by 7 | Viewed by 5362

Abstract

Four commercial viscosity index improvers (VII) have been used to investigate the behavioral differences of these compounds in three types of universally applicable base oils. The used VIIs are structurally three types of co-polymer: ethylene-propylene, star isoprene, and two di-block styrene-isoprene. After dissolving [...] Read more.

Four commercial viscosity index improvers (VII) have been used to investigate the behavioral differences of these compounds in three types of universally applicable base oils. The used VIIs are structurally three types of co-polymer: ethylene-propylene, star isoprene, and two di-block styrene-isoprene. After dissolving of different amounts of VIIs in different base oils, the kinematic viscosities at two standard temperatures were determined and the intrinsic viscosities were calculated according to Huggins method, then the effects of changes in base oil and polymer type were investigated. Intrinsic viscosities as criteria for polymer molecules sizes were found to be higher at lower temperature than at higher temperature. Dependence of intrinsic viscosity on the polymer molecular weight was observed. In the previous works, one or two types of VIIs were studied in only one type of base oil and/or solvent, not different base oils. Furthermore, different ranges of temperatures and concentrations not necessarily applied ranges were selected, but in this work, common base oils and most commercial VIIs were used and the viscometric properties were compared at two temperatures. Viscosities at these temperatures are used for determining VI and definition of lubricant’s viscosity grades. VI improvement is the main cause of VII usage. Full article

(This article belongs to the Topic Tribology: Latest Advances and Prospects)

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17 pages, 5629 KiB

Open AccessArticle

Non-Hertzian Elastohydrodynamic Contact Stress Calculation of High-Speed Ball Screws

by Tiewei Sun, Min Wang, Xiangsheng Gao and Yingjie Zhao

Appl. Sci. 2021, 11(24), 12081; https://doi.org/10.3390/app112412081 - 18 Dec 2021

Cited by 4 | Viewed by 3648

Abstract

In order to eliminate the calculation error of the Hertzian elastohydrodynamic contact stress due to the asymmetry of the contact region of the helix raceway, a non-Hertzian elastohydrodynamic contact stress calculation method based on the minimum excess principle was proposed. Firstly, the normal [...] Read more.

In order to eliminate the calculation error of the Hertzian elastohydrodynamic contact stress due to the asymmetry of the contact region of the helix raceway, a non-Hertzian elastohydrodynamic contact stress calculation method based on the minimum excess principle was proposed. Firstly, the normal contact stresses of the screw raceway and the nut raceway were calculated by the Hertzian contact theory and the minimum excess principle, respectively. Subsequently, the Hertzian solution and the non-Hertzian solution of the elastohydrodynamic contact stress could be determined by the Reynolds equation under different helix angles and screw speeds. Finally, the friction torque test of the double-nut ball screws was designed and implemented on a self-designed bed for validation of the proposed method. The comparison showed that the experimental friction torque was the good agreement with the simulated friction torque, which verified the effectiveness and correctness of the non-Hertzian elastohydrodynamic contact stress calculation method. Under the large helix angle, the calculation accuracy of asperity contact stress for the non-Hertzian solution was more accurate than that of the Hertzian solution at the contact region of ball screws. Therefore, the non-Hertzian elastohydrodynamic contact stress considering the asymmetry of the raceway contact region could more accurately analyze the wear depth of the high-speed ball screws. Full article

(This article belongs to the Topic Tribology: Latest Advances and Prospects)

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15 pages, 4966 KiB

Open AccessArticle

A Local Adaptive Mesh Refinement for JFO Cavitation Model on Cartesian Meshes

by Wanjun Xu, Kang Li, Zhengyang Geng, Mingjie Zhang and Jiangang Yang

Appl. Sci. 2021, 11(21), 9879; https://doi.org/10.3390/app11219879 - 22 Oct 2021

Cited by 5 | Viewed by 2363

Abstract

Nonuniform mesh is beneficial to reduce computational cost and improve the resolution of the interest area. In the paper, a cell-based adaptive mesh refinement (AMR) method was developed for bearing cavitation simulation. The bearing mesh can be optimized by local refinement and coarsening, [...] Read more.

Nonuniform mesh is beneficial to reduce computational cost and improve the resolution of the interest area. In the paper, a cell-based adaptive mesh refinement (AMR) method was developed for bearing cavitation simulation. The bearing mesh can be optimized by local refinement and coarsening, allowing for a reasonable solution with special purpose. The AMR algorithm was constructed based on a quadtree data structure with a Z-order filling curve managing cells. The hybrids of interpolation schemes on hanging nodes were applied. A cell matching method was used to handle periodic boundary conditions. The difference schemes at the nonuniform mesh for the universal Reynolds equation were derived. Ausas’ cavitation algorithm was integrated into the AMR algorithm. The Richardson extrapolation method was employed as an a posteriori error estimation to guide the areas where they need to be refined. The cases of a journal bearing and a thrust bearing were studied. The results showed that the AMR method provided nearly the same accuracy results compared with the uniform mesh, while the number of mesh was reduced to 50–60% of the number of the uniform mesh. The computational efficiency was effectively improved. The AMR method is suggested to be a potential tool for bearing cavitation simulation. Full article

(This article belongs to the Topic Tribology: Latest Advances and Prospects)

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17 pages, 6688 KiB

Open AccessArticle

A Novel Approach of Studying the Fluid–Structure–Thermal Interaction of the Piston–Cylinder Interface of Axial Piston Pumps

by Junjie Zhou, Tianrui Li and Dongyun Wang

Appl. Sci. 2021, 11(19), 8843; https://doi.org/10.3390/app11198843 - 23 Sep 2021

Cited by 6 | Viewed by 2418

Abstract

The friction in the swash plate type axial piston pumps is mainly influenced by the fluid film in the friction interface. The piston–cylinder interface is one of the key friction interfaces in the pumps. The film geometry is determined by the gap between [...] Read more.

The friction in the swash plate type axial piston pumps is mainly influenced by the fluid film in the friction interface. The piston–cylinder interface is one of the key friction interfaces in the pumps. The film geometry is determined by the gap between the piston and the cylinder. The dimensions of the parts determine the gap geometry, and the deformation of the structure also influences the gap geometry. The fluid viscosity is strongly influenced by temperature. Thus, a novel approach of studying the fluid film, the structure, and temperature interaction is provided in this paper. A full and quick fluid–structure–thermal interaction simulation is realized. Then, a dynamic model of the piston–cylinder interface, which integrated the fluid–structure–thermal interacting effects, has been developed. Finally, an approach for calculating the extra friction force between the piston and the cylinder is provided. Compared with the measurement data, the simulation results of the axial friction force achieve a good fit. The present work allows a fast prediction and detailed support for designing the piston–cylinder interfaces. Full article

(This article belongs to the Topic Tribology: Latest Advances and Prospects)

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17 pages, 5087 KiB

Open AccessArticle

Numerical Investigation of Erosion Wear Characteristics of Hydraulic Spillway

by Cong Zhang, Yuqi Zhang, Huadong Zhao, Mao Wang and Tongtong Wang

Appl. Sci. 2021, 11(17), 8118; https://doi.org/10.3390/app11178118 - 31 Aug 2021

Viewed by 1856

Abstract

There are many sand-laden waters in China, and the wear of hydraulic structures caused by sand-laden water diversion has been paid more and more attention. Taking the spillway of a reservoir as the research object, the numerical model of erosion wear caused by [...] Read more.

There are many sand-laden waters in China, and the wear of hydraulic structures caused by sand-laden water diversion has been paid more and more attention. Taking the spillway of a reservoir as the research object, the numerical model of erosion wear caused by sediment-laden particle flows on the spillway was established by using the computational fluid dynamics (CFD) method, VOF (Volume of Fluid) multiphase flow model and DPM (Discrete Phase Model). Through the simulation analysis of the spillway’s overall erosion, the distribution of the spillway erosion wear was obtained. Then, according to the main wear parts, the single variable, such as sediment diameter, sediment concentration, flow velocity and gate opening degree, was changed to study the erosion amount of the spillway and the distribution law of the spillway erosion parts. The results show that the main erosion sites of the spillway are at the bottom of the gate chamber and the middle section of the spillway. The maximum erosion increases linearly with the increase in sediment concentration. With the increase in sediment concentration, the sediment concentration changed from 1 kg/m³ to 6 kg/m³, and the maximum erosion of the spillway increased from 2.58 × 10⁻⁷ kg/m² to 1.53 × 10⁻⁶ kg/m². The erosion at the bottom of the spillway and gate leaf increases first and then decreases with the increase in sediment diameter and reaches the maximum value when the particle size is 0.002 mm. The erosion at the bottom of the spillway and the gate leaf increases with different growth trends as the flow velocity increases, when the flow velocity increases from 2 m/s to 9 m/s and the maximum erosion amount at the bottom of the spillway increases from 3.66 × 10⁻⁷ kg/m² to 1.14 × 10⁻⁶ kg/m², and the maximum erosion of the gate leaf increased from 1.66 × 10⁻⁸ kg/m² to 8.98 × 10⁻⁶ kg/m². The erosion amount at the bottom of the spillway increases with the increase in the gate opening between 0 and 3 m and tends to be stable when the gate opening is greater than 3 m. The maximum erosion position moves to the rear part of the spillway with the change in the gate opening. The change in the gate opening has no obvious effect on the erosion amount of the gate leaf but only changes the area of the gate erosion part. Thus, the erosion wear distribution of spillway under different work conditions is summarized, and the qualitative study between the erosion wear and the distribution of sediment diameter, sediment concentration, flow velocity and gate opening degree is made. Full article

(This article belongs to the Topic Tribology: Latest Advances and Prospects)

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15 pages, 2873 KiB

Open AccessFeature PaperArticle

Transient Nanoscale Tribofilm Growth: Analytical Prediction and Measurement

by Michael Leighton, Nick Morris and Homer Rahnejat

Appl. Sci. 2021, 11(13), 5890; https://doi.org/10.3390/app11135890 - 24 Jun 2021

Cited by 3 | Viewed by 1778

Abstract

A new method for the simultaneous in situ measurement and characterisation of molybdenum-based tribofilms is presented, based on lateral force microscopy. The simultaneity of measurements is crucial for a fundamental understanding of the tribochemical phenomena. A new analytical method is also presented, which [...] Read more.

A new method for the simultaneous in situ measurement and characterisation of molybdenum-based tribofilms is presented, based on lateral force microscopy. The simultaneity of measurements is crucial for a fundamental understanding of the tribochemical phenomena. A new analytical method is also presented, which combines a BET multi-layer adsorption/desorption model for boundary-active lubricant species-surface combination with the modified shear-promoted thermal activation Arrhenius equation. Therefore, the expounded method integrates the mechanical, physical and chemical aspects of the adsorption-bonding process as a detailed multi-step phenomenon. The method provides detailed explanations of the measured tribofilm growth, in a fundamental manner, not hitherto reported in the literature. Therefore, the combined experimental methodology and modelling approach provides a significant advance in the understanding of tribofilm formation. Furthermore, the developed model has the potential to explain the behaviour of many complex lubricant formulations and the resulting multi-species tribofilms, generated through synergistic and/or antagonistic constituent adsorption and shear-promoted activation. Full article

(This article belongs to the Topic Tribology: Latest Advances and Prospects)

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