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Fadaei Naeini, V., Björling, M., Larsson, J. A. & Larsson, R. (2025). Tribochemistry of glycerol-water mixtures confined between ferrous substrates: An atomic-scale concept by reactive molecular dynamics simulation. Tribology International, 202, Article ID 110322.
Open this publication in new window or tab >>Tribochemistry of glycerol-water mixtures confined between ferrous substrates: An atomic-scale concept by reactive molecular dynamics simulation
2025 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 202, article id 110322Article in journal (Refereed) Published
Abstract [en]

In this study, non-equilibrium molecular dynamics (NEMD) simulations with a reactive force field were used to investigate the tribochemical properties of glycerol, with and without water, confined between two ferrous surfaces. The results demonstrated that glycerol significantly reduced friction on α-Fe slabs more effectively than on functionalized amorphous magnetite. A numerical method was introduced to identify the interface region and evaluate the dissociated surface atoms. It was found that the dissociation rate of glycerol molecules increased with applied normal pressure and shear stress. Additionally, the production rate of water molecules from glycerol dissociation was consistently positive for all solutions above 80 % wt. The assumption of linear velocity distribution across the film thickness was validated for all systems studied.

Place, publisher, year, edition, pages
Elsevier Ltd, 2025
Keywords
Glycerol, Dissociation rate, Mechanochemistry, Reactive MD simulation
National Category
Physical Chemistry Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Applied Physics; Machine Elements
Identifiers
urn:nbn:se:ltu:diva-110498 (URN)10.1016/j.triboint.2024.110322 (DOI)2-s2.0-85206239912 (Scopus ID)
Funder
The Kempe Foundations, JCK-1903.2Knut and Alice Wallenberg Foundation
Note

Validerad;2024;Nivå 2;2024-11-26 (hanlid);

Full text license: CC BY 4.0

Available from: 2024-10-22 Created: 2024-10-22 Last updated: 2024-11-26Bibliographically approved
Higashitani, Y., Kawabata, S., Björling, M. & Almqvist, A. (2024). A traction coefficient formula for EHL point contacts operating in the linear isothermal region. Tribology International, 193, Article ID 109452.
Open this publication in new window or tab >>A traction coefficient formula for EHL point contacts operating in the linear isothermal region
2024 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 193, article id 109452Article in journal (Refereed) Published
Abstract [en]

Many mechanical systems including rolling/sliding parts, require traction data across a spectrum of operating conditions to predict their motion effectively. Numerous studies have examined the thermal effects and shear-thinning concerning the traction curve, but only a few have focused on the traction coefficient in the linear isothermal regime for low SRR. In this work, we investigate traction coefficient characteristics of EHL point contacts in the linear isothermal regime, over a wide range of operational conditions. To this end, we conduct numerical simulations utilizing a fully-coupled finite element-based model, resulting in a prediction formula for the traction coefficient slope. With this formula, the traction coefficient slope could be predicted for the operating conditions considered.

Place, publisher, year, edition, pages
Elsevier, 2024
Keywords
Modelling, Lubrication, EHL, Friction, Traction, FEM, Rolling/sliding, Machine Element
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-104213 (URN)10.1016/j.triboint.2024.109452 (DOI)001196823200001 ()2-s2.0-85185836521 (Scopus ID)
Note

Validerad;2024;Nivå 2;2024-03-28 (signyg);

Full text license: CC BY 4.0;

Funder: DENSO CORPORATION; 

This article has previously appeared as a manuscript in a thesis.

Available from: 2024-02-07 Created: 2024-02-07 Last updated: 2024-08-22Bibliographically approved
Prajapati, D. K., Hansen, J. & Björling, M. (2024). An assessment of the effect of surface topography on coefficient of friction for lubricated non-conformal contacts. Frontiers in Mechanical Engineering, 10, Article ID 1360023.
Open this publication in new window or tab >>An assessment of the effect of surface topography on coefficient of friction for lubricated non-conformal contacts
2024 (English)In: Frontiers in Mechanical Engineering, E-ISSN 2297-3079, Vol. 10, article id 1360023Article in journal (Refereed) Published
Abstract [en]

Determining an accurate state of lubrication is of utmost importance for the precise functionality of machine elements and to achieve elongated life and durability. In this work, a homogenized mixed-lubrication model is developed to study the effect of surface topographies on the coefficient of friction. Various measured real surface topographies are integrated in the model using the roughness homogenization method. The shear-thinning behavior of the lubricant is incorporated by employing the Eyring constitutive relation. Several Stribeck curves are generated to analyze the effect of roughness lays and root mean square (RMS) roughness on the coefficient of friction. The homogenized mixed lubrication model is validated against experimental rolling/sliding ball-on-disc results, and a good agreement between simulated and experimental coefficient of friction is found.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2024
Keywords
mixed-lubrication, coefficient of friction, surface roughness lay, roughness homogenization, shear thinning, two-scale modeling, non-conformal contacts
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-104358 (URN)10.3389/fmech.2024.1360023 (DOI)001160493900001 ()2-s2.0-85184727548 (Scopus ID)
Funder
The Kempe Foundations, SMK-2043
Note

Validerad;2024;Nivå 2;2024-04-02 (signyg);

Full text license: CC BY

Available from: 2024-02-22 Created: 2024-02-22 Last updated: 2024-04-02Bibliographically approved
Higashitani, Y., Kawabata, S., Björling, M. & Almqvist, A. (2024). Computational domain optimization for circular EHL contacts. Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, 238(12), 1512-1530
Open this publication in new window or tab >>Computational domain optimization for circular EHL contacts
2024 (English)In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 238, no 12, p. 1512-1530Article in journal (Refereed) Published
Abstract [en]

This paper introduces an optimized computational domain for fully flooded circular elastohydrodynamic lubrication (EHL) contacts, enhancing the accuracy of numerical calculations of pressure and oil film thickness. First, the computational domain was configured based on Kapitza's analytical solution. Then, a resolution sensitivity study for the mesh of the 2D computational domain for the Reynolds equation was conducted to investigate the effect of mesh resolution on the accuracy of the numerical solution. Subsequently, the impact of the size of the full 3D computational domain on the simulation's accuracy and computational efficiency was analyzed. The main result is the 3D computational domain, which automatically adapts to operating conditions within the piezoviscous rigid, the isoviscous rigid, the piezoviscous elastic, and the isoviscous elastic regions, as well as in the transition regions between them. This results in a model which provides accurate predictions across a wide range of operational conditions. Another outcome is a new approximate expression for the central oil film thickness, showing a maximum relative difference of less than 4.6% compared to the numerical model.

Place, publisher, year, edition, pages
Sage Publications, 2024
Keywords
Point contacts, fully-coupled finite-element approach, elastohydrodynamic lubrication, oil film thickness, numerical starvation
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-104212 (URN)10.1177/13506501241264085 (DOI)001288890800001 ()2-s2.0-85200969602 (Scopus ID)
Note

Validerad;2024;Nivå 2;2024-11-11 (joosat);

Funder: Denso Corporation;

This article has previously appeared as a manuscript in a thesis.

Available from: 2024-02-07 Created: 2024-02-07 Last updated: 2024-11-20Bibliographically approved
Chen, J., Björling, M., Marklund, P. & Shi, Y. (2024). Effect of anti-icing coating functional groups on ice adhesion. Applied materials today, 39, Article ID 102264.
Open this publication in new window or tab >>Effect of anti-icing coating functional groups on ice adhesion
2024 (English)In: Applied materials today, ISSN 2352-9407, Vol. 39, article id 102264Article in journal (Refereed) Published
Abstract [en]

Unwanted ice build-up is a ubiquitous phenomenon in nature, which creates a series of catastrophic impacts on a wide range of human activities. Various anti/de-icing materials have been proposed for dealing with icing issues. Superhydrophobic anti/de-icing coatings have been widely reported since it has high efficiency and can be achieved in different ways. The surface functional groups have a significant influence on surface energy which is related to surface wettability. However, the influence of the coating surfaces functional groups on the anti-/de-icing properties is still not well studied. To investigate this influence, different groups with different hydrophilicity have been introduced to 3,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluorooctyl acrylate (TFOA) to fabricate several branch copolymer ice-phobic coatings. The anti-icing performance and the influence of group radius and interaction were studied. The acrylic acid TFOA showed a great superhydrophobic property (over 150° water contact angle), lower ice adhesion strength (<50 kPa), and lower wear depth compared with other copolymer coatings. The mechanism was studied via the molecular dynamic calculation carried out in ChemDraw software. The interaction between hydrophobic and hydrophilic groups and the steric length of the hydrophilic groups influence the surface structure and surface element distribution, further influencing the ice adhesion strength.

Place, publisher, year, edition, pages
Elsevier, 2024
Keywords
Radius, Hydrogen bond, van der Walls gap, Ice adhesion
National Category
Manufacturing, Surface and Joining Technology
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-105227 (URN)10.1016/j.apmt.2024.102264 (DOI)001251708000001 ()2-s2.0-85194943479 (Scopus ID)
Funder
Swedish Research Council Formas, 2019–00904, 2022–01988, 2022–01047Swedish Research Council, 2019–04941
Note

Validerad;2024;Nivå 2;2024-06-10 (hanlid);

Full text license: CC BY

Available from: 2024-04-24 Created: 2024-04-24 Last updated: 2024-11-20Bibliographically approved
Mehamud, I., Björling, M., Marklund, P., An, R. & Shi, Y. (2024). Enhanced Machine Condition Monitoring Based on Triboelectric Nanogenerator (TENG): A Review of Recent Advancements. Advanced Sustainable Systems, Article ID 2400575.
Open this publication in new window or tab >>Enhanced Machine Condition Monitoring Based on Triboelectric Nanogenerator (TENG): A Review of Recent Advancements
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2024 (English)In: Advanced Sustainable Systems, E-ISSN 2366-7486, article id 2400575Article, review/survey (Refereed) Epub ahead of print
Abstract [en]

Intelligent machine condition monitoring is desirable to enable Industry 4.0 and 5.0 to create sustainable products and services via the integration of automation, data exchange, and human–machine interface. In the past decades, huge progress has been achieved in establishing sustainable machine condition monitoring systems via various sensing technologies. Yet, the dependence on external power sources or batteries for sensing and data communication remains a challenge. In addition, energy harvesting and sensing are dynamically growing research fields introducing various working mechanisms and designs for improved performance, flexibility, and integrability. Recently, triboelectric nanogenerators (TENG) have been applied as a new technology for energy harvesting and sensing to monitor machine performance. This manuscript presents the potential application of TENG for self-powered sensors and energy harvesting technology for machine condition monitoring, where the developmental aspects of TENG-based devices including the robustness of design and device integration to machine elements are reviewed. For better comparison, the performance of various reported devices is summarized. Simultaneously, the advanced results achieved in employing TENGs for various condition analysis techniques and self-powered wireless communication for machine condition monitoring are discussed. Finally, the challenges, and key strategies for utilizing TENGs for machine condition monitoring in the future, are presented. 

Place, publisher, year, edition, pages
John Wiley and Sons Inc, 2024
Keywords
condition monitoring, energy harvesting, self-powered, TENG, triboelectric nanogenerator
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Energy Engineering
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-110240 (URN)10.1002/adsu.202400575 (DOI)001319583300001 ()2-s2.0-85204779577 (Scopus ID)
Funder
Swedish Research Council, 2019–04941, 2023–04962
Note

Full text license: CC BY

Available from: 2024-10-16 Created: 2024-10-16 Last updated: 2024-11-20
Shi, Y., Björling, M. & Larsson, R. (2024). Glycerol-based lubricants for electric vehicles. In: Leonardo I. Farfan-Cabrera, Ali Erdemir (Ed.), Electric Vehicle Tribology: Challenges and Opportunities for a Sustainable Transportation Future: (pp. 291-301). Elsevier
Open this publication in new window or tab >>Glycerol-based lubricants for electric vehicles
2024 (English)In: Electric Vehicle Tribology: Challenges and Opportunities for a Sustainable Transportation Future / [ed] Leonardo I. Farfan-Cabrera, Ali Erdemir, Elsevier , 2024, p. 291-301Chapter in book (Other academic)
Place, publisher, year, edition, pages
Elsevier, 2024
Keywords
DLC, Glycerol, lubrication, superlubricity, water
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-108663 (URN)10.1016/B978-0-443-14074-7.00017-0 (DOI)2-s2.0-85199048493 (Scopus ID)978-0-443-14074-7 (ISBN)
Available from: 2024-08-21 Created: 2024-08-21 Last updated: 2024-08-21Bibliographically approved
Chen, J., Parsi, P. K., Marklund, P., Björling, M. & Shi, Y. (2024). Graphene-enhanced, wear-resistant and thermal-conductive, anti-/de-icing Gelcoat composite coating. Advanced Composites and Hybrid Materials, 7(1), Article ID 9.
Open this publication in new window or tab >>Graphene-enhanced, wear-resistant and thermal-conductive, anti-/de-icing Gelcoat composite coating
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2024 (English)In: Advanced Composites and Hybrid Materials, ISSN 2522-0128, Vol. 7, no 1, article id 9Article in journal (Refereed) Published
Abstract [en]

Wind power is considered as a sustainable and environmentally friendly energy source. However, the occurrence of icing poses significant challenges to energy production, particularly in frigid regions during the winter season. Conventional strategies employed for preventing and removing ice formation have proven inadequate due to their inability to satisfy intricate requirements or their high energy consumption. In this study, a commercial gelcoat coating was adopted as an anti-/de-icing coating by introducing different concentrations of graphene and boron nitride into the gelcoat coating through physical mixing. Extensive investigations were conducted on the correlation between anti-/de-icing, wear resistance, and thermal conductivity. Notably, the incorporation of nanoparticles induced a rise in the surface roughness, resulting in prolonged resistance to water icing on the coated surface. The wear resistance and thermal conductivity of the composite coating were enhanced through the inclusion of boron nitride and graphene. The building of thermal conductive particle networks improved thermal conductivity which can lead to improved heat transfer and heat distribution. At the same time, the enhanced gelcoat composite coating exhibited exceptional passive anti-/de-icing performance and wear resistance. This coating can replace commercial coatings to improve anti-/de-icing efficiency for the existing active heating anti-/de-icing techniques available in the market.

In this study, we aimed to enhance the wear resistance, thermal conductivity, and anti-/de-icing properties of a gelcoat composite coating by incorporating graphene and boron nitride. The gelcoat graphene coating showed better performance than the gelcoat boron nitride coating and pure gelcoat coating. The improved wear resistance of the gelcoat graphene coating can be attributed to the two-dimensional layer structure of graphene, while the addition of graphene resulted in a threefold increase in the thermal conductivity of the gelcoat composite coating compared to the pure gelcoat coating. The gelcoat composite coatings exhibited a high-water contact angle and low ice adhesive force. It was observed that as the surface roughness increased, the water contact angle also increased. The increase in ice adhesion after abrasion proves that abrasion is always detrimental to de-icing. Despite the extension of icing delay time, the large number of grooves and bumps created by wear results in stronger mechanical interlocking. It is worth mentioning that gelcoat graphene coating still demonstrated lower ice adhesive strength than gelcoat boron nitride coating and pure gelcoat coating. Overall, we successfully developed a gelcoat graphene coating with improved thermal conductivity, wear resistance, and low ice adhesive properties. This novel composite coating has the potential to significantly enhance the efficiency of existing heating technologies for anti-/de-icing applications, thereby reducing energy consumption associated with the turbine blades’ anti-/de-icing system.

Place, publisher, year, edition, pages
Springer Nature, 2024
Keywords
Graphene, Wear, Coating, Anti-/de-icing
National Category
Manufacturing, Surface and Joining Technology
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-103447 (URN)10.1007/s42114-023-00820-3 (DOI)001137939500002 ()2-s2.0-85181582111 (Scopus ID)
Funder
Swedish Research Council Formas, 2019–00904Swedish Research Council, 2019– 04941Swedish Energy Agency, 2018–003910Interreg Nord, 20202472
Note

Validerad;2024;Nivå 2;2024-04-02 (hanlid);

Full text license: CC BY 4.0

Available from: 2024-01-02 Created: 2024-01-02 Last updated: 2024-08-22Bibliographically approved
Johansson, P., Marklund, P., Björling, M. & Shi, Y. (2024). Mechanisms behind the environmental sensitivity of carbon fiber reinforced polytetrafluoroethylene (PTFE). Friction, 12(5), 997-1015
Open this publication in new window or tab >>Mechanisms behind the environmental sensitivity of carbon fiber reinforced polytetrafluoroethylene (PTFE)
2024 (English)In: Friction, ISSN 2223-7690, E-ISSN 2223-7704, Vol. 12, no 5, p. 997-1015Article in journal (Refereed) Published
Abstract [en]

Carbon fiber reinforced polytetrafluoroethylene (CF/PTFE) composites are known for their exceptional tribological performance when sliding against steel or cast iron in inert gas environments. Compared to experiments in humid air, about an order of magnitude lower wear rate and several times lower coefficient of friction have been reported for tests conducted in dry nitrogen and hydrogen. Moreover, trace moisture has been shown to affect the friction and wear significantly of this tribosystem, although a possible effect of oxygen cannot be ruled out due to uncertainties regarding the oxygen concentrations. While several studies have pointed out the environmental sensitivity of CF/PTFE, the understanding of the underlying mechanisms are very limited. The objective of this research is to investigate the individual and combined effect of oxygen and moisture on the tribological behavior of CF/PTFE sliding against steel. Additionally, this study aims to elucidate the underlying mechanisms that govern the environmental sensitivity of the system. Climate-controlled three-pin-on-disc experiments were conducted in nitrogen atmospheres at various concentrations of oxygen and moisture. The tribological results clearly demonstrate that both moisture and oxygen contribute to increased friction and wear. However, the adverse effect was much more pronounced for oxygen than moisture. A qualitative method was developed to estimate the tribofilm coverage on the CF/PTFE surface. Results showed strong correlation between high coverage of strongly adhered tribofilm and low wear rate. Moreover, a loosely adhered tribofilm was observed on top of the CF/PTFE surface in presence of moisture. FTIR analysis indicated that the loosely adhered tribofilm found in the moisture-enriched environment contained a significant amount of adsorbed water, which may explain the lower coefficient of friction in presence of moisture compared to oxygen. The adsorbed water in the loosely adhered tribofilm could be an indication of moisture-driven lubrication by the non-graphitic carbon in the tribofilm.

Place, publisher, year, edition, pages
Springer Nature, 2024
Keywords
polymer composite, tribofilm, tribochemistry, atmosphere
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-101605 (URN)10.1007/s40544-023-0824-9 (DOI)001113623800003 ()2-s2.0-85178446936 (Scopus ID)
Note

Validerad;2024;Nivå 2;2024-04-02 (hanlid);

Full text license: CC BY 4.0

Available from: 2023-10-09 Created: 2023-10-09 Last updated: 2024-04-02Bibliographically approved
Zapata Tamayo, J. G., Björling, M., Shi, Y., Hardell, J. & Larsson, R. (2024). Micropitting performance and friction behaviour of DLC coated bearing steel surfaces : On the influence of Glycerol-based lubricants. Tribology International, 196, Article ID 109674.
Open this publication in new window or tab >>Micropitting performance and friction behaviour of DLC coated bearing steel surfaces : On the influence of Glycerol-based lubricants
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2024 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 196, article id 109674Article in journal (Refereed) Published
Abstract [en]

A better understanding about the rolling contact fatigue and micropitting performance of machine component surfaces lubricated with environmentally friendly lubricants is critical to designing and further formulating new lubricants intended to be used in rolling–sliding contacts such as those found in gear and bearing applications. In this work, the frictional behaviour and rolling contact fatigue (RCF) performance of DLC, Cr/a-WC:H/a-C:H and a-C:Cr coatings under glycerol-based lubrication in rolling sliding contact conditions have been investigated. Traction maps, Stribeck curves, and fatigue plots have been generated by using a micropitting test rig (MPR). The initiation and progression of micropitting was monitored by means of white light optical interferometry and scanning electron microscopy (SEM). Results indicated that glycerol-based lubricants exhibited a significant friction reduction as the hydrodynamic effect is enhanced at higher rolling-speeds. Under boundary lubrication the friction coefficient was significantly higher compared to the values obtained with a commercial mineral-based transmission oil. Compared to uncoated steel surfaces, DLC coatings effectively reduced the volume loss and micropitting progression. Irrespective of the coating thickness, DLC showed an excellent tribological behaviour when the base lubricant favours the onset of mild-wear, over micropitting. When the lubricant formulation favoured the onset of micropitting, the coatings tended to prematurely fail due to debonding from the substrate, and local micro-spallation. The experiments demonstrated that friction reduction does not necessarily correspond with a reduction of micropitting.

Place, publisher, year, edition, pages
Elsevier, 2024
Keywords
Micropitting, Surface coating, Glycerol, Rolling contact fatigue
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-105398 (URN)10.1016/j.triboint.2024.109674 (DOI)001232371700001 ()2-s2.0-85190736825 (Scopus ID)
Note

Validerad;2024;Nivå 2;2024-07-02 (joosat);

Full text license: CC BY 4.0;

Funder: Swedish Research Council (2017-04914, 2019-04941); Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning, Formas (2019-00904); 

Available from: 2024-05-08 Created: 2024-05-08 Last updated: 2024-07-02Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-4271-0380

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