Tribology of Electric Vehicles

A special issue of Lubricants (ISSN 2075-4442).

Deadline for manuscript submissions: 31 August 2025 | Viewed by 5322

Special Issue Editors


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Guest Editor
Tribology Research and Evaluations, Fuels and Lubricants Division, Southwest Research Institute, San Antonio, TX, USA
Interests: tribology; electric vehicles; EV fluids; rheology

E-Mail Website
Guest Editor
Tribology Research and Evaluations, Fuels and Lubricants Division, Southwest Research Institute, San Antonio, TX, USA
Interests: tribology; electric vehicles; EV fluids; rheology

Special Issue Information

Dear Colleagues,

The shift towards electrification in the automotive industry has presented new challenges in the field of lubrication. While the number of moving parts in a battery electric vehicle (BEV) has reduced significantly versus those in internal combustion engine (ICE) vehicles, the tribological concerns facing electric vehicles (EVs) reach beyond traditional ICE vehicles. BEVs are significantly heavier than ICE vehicles, placing more load on the wheel bearings and tires. In addition, the driveline fluids, historically made to protect gears from scuffing and pitting and provide traction characteristics for clutches, now have to operate at greatly increased rotational speeds, operate in an environment with stray electric currents, and in many cases act as a coolant in direct contact with the motor and inverter. They must also continue to protect the gears from pitting and scuffing. These challenging requirements have created a need for new base fluids and additives.

Traditional test methods for ICE fluids are not entirely suitable for understanding the behavior of EV fluids. Early research has shown that the presence of the electric field has an effect on material performance in terms of friction and wear. Fluid properties such as viscosity are also affected. This collection of manuscripts will present various approaches to studying EV fluid and grease properties. Test method development, analysis of initial findings, and thoughtful discussions will be presented.

Dr. Peter M. Lee
Dr. Carlos Sanchez
Guest Editors

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Keywords

  • tribology
  • electric vehicles
  • EV fluids
  • rheology

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Published Papers (3 papers)

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Research

14 pages, 9081 KiB  
Article
Non-Polar Chain-Enabled Suspension of Carbon Nanoparticles in Base Oil
by M. Humaun Kabir, Darrius Dias, Evan Johnson, Joe Kosmoski and Hong Liang
Lubricants 2024, 12(11), 373; https://doi.org/10.3390/lubricants12110373 - 29 Oct 2024
Cited by 1 | Viewed by 741
Abstract
The transition to electric vehicles (EVs) has introduced new challenges in lubrication, demanding innovative solutions to ensure consistent performance. One promising approach is the use of nanoparticle additives, which have the potential to improve lubrication performance significantly. However, achieving a stable suspension of [...] Read more.
The transition to electric vehicles (EVs) has introduced new challenges in lubrication, demanding innovative solutions to ensure consistent performance. One promising approach is the use of nanoparticle additives, which have the potential to improve lubrication performance significantly. However, achieving a stable suspension of these nanoparticles in lubricating oils remains a critical challenge, as suspension stability is essential for maintaining consistent performance and maximizing the benefits of these advanced additives. In this study, carbon nanoparticles (CNPs) were modified with dodecylamine (DDA) to achieve stable suspension in nonpolar fluids. The successful functionalization was confirmed by the FTIR results, which showed characteristic peaks of various bonding. The suspension stability tests demonstrated that DDA-CNPs remained suspended for over 60 days in the Polyalphaolefin (PAO) oil, whereas unmodified CNPs were sedimented within 3–7 days. The rheological behavior was measured under different shear rates and temperatures. Viscosity measurements indicated that DDA-CNPs maintained a lower value compared to base PAO. The lubricants’ friction coefficient (COF) was also determined under various speeds and loads. The addition of DDA-CNPs at a concentration of 0.05 wt.% resulted in a significant reduction in COF, with values decreasing by 26% compared to base PAO oil under a load of 1 N. Additionally, the COF for DDA-CNPs was consistently lower than that of PAO, with reductions ranging from 15% to 18% across all tested speeds. The Stribeck curve further highlighted the improved performance of DDA-CNPs across boundary, mixed, and hydrodynamic lubrication regimes. These findings suggest that DDA-CNPs significantly improve the lubrication performance of PAO oil, making them suitable for advanced lubrication applications in automotive and industrial systems. Full article
(This article belongs to the Special Issue Tribology of Electric Vehicles)
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22 pages, 12430 KiB  
Article
Electrification of a Mini Traction Machine and Initial Test Results
by Peter Lee, Carlos Sanchez, Michael Moneer and Andrew Velasquez
Lubricants 2024, 12(10), 337; https://doi.org/10.3390/lubricants12100337 - 30 Sep 2024
Viewed by 1285
Abstract
Electric vehicles (EVs) continue to evolve, and sales continue to increase as the world pushes toward improved sustainability. This drives the need for research to understand the unique environments in which fluids operate within the Electric Drive Units (EDUs) of EVs in order [...] Read more.
Electric vehicles (EVs) continue to evolve, and sales continue to increase as the world pushes toward improved sustainability. This drives the need for research to understand the unique environments in which fluids operate within the Electric Drive Units (EDUs) of EVs in order to improve durability and reduce frictional losses. However, for this to happen, test rigs are required to operate with an electric current passing across the test parts and through the lubricant. Very few electrified test rigs currently exist, with most being adaptations of rigs undertaken by academia and independent and national research labs. In this work, the PCS Mini Traction Machine (MTM) was modified to supply a voltage across a tribological contact. New parts for the MTM were designed in collaboration with the instrument manufacturer. Work was undertaken in both the author’s labs and the manufacturer’s labs with the aim of bringing a commercially available unit to market as quickly as possible. A test matrix was completed on the MTM utilizing a range of temperatures, loads, and voltage inputs for three different lubricants commonly used in EDUs. The test matrix consisted of 36 test conditions, with some runs performed in triplicate, resulting in 81 tests for each oil and a total matrix of 243 tests. The test matrix was run to obtain the results and to test the robustness of the rig design. After testing was completed, the MTM disc wear scars were measured. The results from these measurements indicate that the application of alternating current (AC) and direct current (DC) causes a significant increase in the wear scar compared to non-electrified test conditions. This, in turn, results in increased traction values under non-electrified conditions. It was also noted that the repeatability of the traction curves and end-of-test wear was reduced under both AC and DC electrified conditions. Full article
(This article belongs to the Special Issue Tribology of Electric Vehicles)
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16 pages, 10786 KiB  
Article
Exploring the Boundaries of Electrically Induced Bearing Damage in Grease-Lubricated Rolling Contacts
by Jack R. Janik, Sudip Saha, Robert L. Jackson and German Mills
Lubricants 2024, 12(8), 268; https://doi.org/10.3390/lubricants12080268 - 28 Jul 2024
Viewed by 2462
Abstract
As public attention is increasingly drawn toward more sustainable transportation methods, the popularity of electric vehicles (EVs) as part of the solution is rapidly expanding. Operating conditions within EVs can be severe compared to standard combustion powertrains, and the risk of electrical arcing [...] Read more.
As public attention is increasingly drawn toward more sustainable transportation methods, the popularity of electric vehicles (EVs) as part of the solution is rapidly expanding. Operating conditions within EVs can be severe compared to standard combustion powertrains, and the risk of electrical arcing across mechanical surfaces from electric leakage currents incites additional concern. This study employed a series of electro-tribological tests utilizing various moving patterns to improve understanding of the driving conditions for electrically induced bearing damage (EIBD). Rolling ball-on-disk tests were performed with different polyurea-thickened greases. Rotational tests were initially run at various speeds and test durations, but electrical damage was limited. However, electrical damage was unmistakable when a reciprocating motion was used at different track lengths and speeds. These results suggest that the conditions associated with the track length, such as the number of directional changes and speed-dependent film thickness, play a considerable role in forming electrical damage. This work provides critical insights into the mechanisms of EIBD in EVs and other electrical systems. It highlights the importance of understanding the operational conditions that contribute to EIBD, which can lead to improved designs and maintenance practices, ultimately enhancing the efficiency and lifespan of these systems. Full article
(This article belongs to the Special Issue Tribology of Electric Vehicles)
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