Molecular and Continuum Models for Lubricants

To accelerate cost-intensive development processes and complement experimental characterizations, we develop multiscale computer models for lubricants ranging from the atomic to the continuum scale. Our models cover a broad spectrum of processes: from the chemical interaction between additives and surfaces to piezoviscosity and shear thinning through to elastohydrodynamics. A particular focus is on lubrication conditions where conventional continuum models reach their limits due to very thin films or high pressures.

• Development of constitutive models for density, viscosity and surface slip
• Development of kinetic models for surface adsorption
• Development of material models such as constitutive equations for the rheology and tribochemistry of lubricants (including solid lubricants) under high pressures and integration into continuum methods
• Molecular dynamics simulations of lubricants under extreme loads (e.g. in rolling bearings and gear pairings)
• Evaluation and optimization of lubricants with respect to their electrotribological suitability as well as development of targeted formulations taking into account electric fields and specific operating conditions
• Qualification and substitution of lubricant additives to enhance the performance of tribological components in a sustainable way.

Reference Projects

LubeTwin

Development of the continuum-physics core of a digital twin for tribological contacts under boundary and mixed lubrication conditions

The ERC-funded LubeTwin project aims to optimize lubrication in machines and technical systems that rely on highly loaded friction contacts. At the heart of the project is the development of a digital twin that models all lubrication regimes - from dry friction to hydrodynamic lubrication. Using advanced molecular dynamics simulations and machine learning, LubeTwin aims to link the atomic processes of friction with macroscopic friction in technical components. This approach is intended to make friction-inducing mechanisms - which are difficult to study experimentally - computationally accessible.

Project Profile: LubeTwin

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Recon

Molecular Dynamics and Continuum Modeling of Highly Sheared Lubricant Films in Boundary Friction

Modern high-performance machines, from electric motors to wind turbine gearboxes, subject lubricants to extreme conditions: pressures in the gigapascal range, shear rates exceeding one million per second, and lubricant films as thin as a single molecule. In this extreme regime, classical computational models fail. The project uses molecular dynamics simulations to develop a physically sound continuum model for precisely this critical lubrication regime, enabling an extension of the engineering-grade Reynolds equation for application in this extreme regime.

Project Profile: ReCon

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Lube.Life

Sensor-based electronic system for the sustainable use of lubricants in industrial plants

The Lube.Life project targeted the development of an innovative approach to predict the behaviour of lubricants under demanding operating conditions. Sensor data, predictive online algorithms and simulated analytical data, including infrared spectra, are combined to provide a comprehensive evaluation of the lubricant. Since contamination, challenging environmental conditions or unplanned operating states can increase a lubricant's potential for damage, the latter is continuously determined online. Particular attention is paid to trigger factors, such as contaminants or compounds formed through chemical reactions, that significantly influence the damage potential.

Project Profile: Lube.Life

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CNTLub

Solid-State Lubrication Using Carbon Nanotubes: Fundamental Understanding of Transfer Layer Formation and Sliding Mechanisms Through Atomistics and Experimental Nanoanalytics

Investigation of the lubrication mechanisms of carbon nanotubes (CNTs) under high-load tribological conditions through multiscale analyses ranging from atomistics to macroscopic applications, with the aim of developing fluid-free, high-performance lubrication systems.

Project Profile: CNTLub

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GraLub

Mechanisms of Graphite Lubrication in Rolling Contacts

Investigation of transfer layer formation and sliding mechanisms of graphite as a solid lubricant in heavily loaded rolling contacts through multiscale experiments and atomistic simulations, with the goal of developing practical concepts for lifetime lubrication of heavily loaded rolling bearings.

Project Profile: GraLub

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PTFELub

Polytetrafluoroethylene Lubrication of Radial Roller Bearings: Controlling Lubricant Transfer Through Cage Design Based on Materials-Specific Requirements

The solid lubricant polytetrafluoroethylene (PTFE) is frequently used in low-load rolling contacts when the use of conventional liquid lubricants is ruled out due to operating conditions such as vacuum or high temperatures. For use in high-load rolling contacts, however, the strength of PTFE is no longer sufficient, and lifetime lubrication is no longer possible. In rolling bearings, a technical solution to compensate for PTFE loss is continuous relubrication, achieved by incorporating PTFE reservoirs into the rolling bearing cage so that lubricant is gradually transferred to the rolling elements. Additionally, the strength of PTFE can be increased by blending it with the high-performance polymer PEEK. As part of the project, the lubrication mechanisms of PTFE were investigated both experimentally (RWTH Aachen) and via atomistic simulations (Fraunhofer IWM), and the feasibility of delivering PTFE to rolling bearings via a transfer film generated between the rolling elements and the cage was demonstrated.

Project Profile: PTFELub

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SupraSlide

Supra-sliding bearings for maximum energy efficiency and precision

SupraSlide aims to bring supra-lubrication from the laboratory into industrial applications. This enables the development of simple, cost-effective sliding bearings with extremely low coefficients of friction and energy savings of up to 90%.

Project Profile: SupraSlide

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Prometheus

High-Performance Carbon Coatings for Friction-Optimized Engine Components

Development of innovative ta-C-based coatings and lubricants for the comprehensive tribological optimization of all critical engine components (valve train, piston rings, cylinder walls, connecting rods) to significantly reduce friction losses in internal combustion engines and thereby cut energy consumption and CO2 emissions by up to 40%.

Project Profile: Prometheus

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Chephren

Chemical-Physical Reduction of Friction Energy - Ultra-Smooth and Superlubricating Coatings for Component Applications

Development of high-performance ta-C-based coatings and innovative tribological systems to achieve superlubricity in machine components, with the aim of significantly reducing energy loss due to friction and thereby lowering CO₂ emissions and resource consumption.

Project Profile: Chephren

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Wear Prediction

Prediction of Wear Using Multiscale and Multiphysics Approaches

In collaboration with partners, Fraunhofer IWM has developed a methodological framework that, for the first time, enables the calculation of wear and friction in rolling bearings and gears across multiple length scales - from atoms to components. This provides a physically sound prediction method for boundary friction and wear that can be applied to other materials-lubricant combinations, thereby reducing the need for empirical testing and shortening development times.

Project Profile: Wear Prediction

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Garcia Manzano, E. J.; Sauer, F.; Haber, M.; Mukherjee, A.; Falk, K.; Schwitzke, C.; Bauer, H. J.; Moseler, M.; Schulze, V., Experimental and multiscale simulation analysis of the lubricant penetration in gear skiving, Production Engineering. Research and development 19/6 (2025) 1373-1394 Link

Peeters, S.; Garcia Manzano, E. J.; Stief, F.; Reichenbach, T.; Falk, K.; Moras, G.; Moseler, M., When wall slip wins over shear flow: A temperature-dependent Eyring slip law and a thermal multiscale model for diamond-like carbon lubricated by a polyalphaolefin oil, Tribology international 214/Part C (2026) Art. 111305, 13 pages Link

Reichenbach, T.; von Goeldel, S.; Peeters, S.; Vokolos, G.; König, F.; Jacobs, G.; Moras, G.; Moseler, M., Polytetrafluoroethylene (PTFE) Lubrication of Rolling Point Contacts by Double Transfer Films: Relationships between Friction and Lubricant Film Distribution Revealed by Spacer Layer Imaging and Molecular Dynamics, Tribology transactions 68/5 (2025) 1102-1113, 12 Seiten  Link

Kruse, L.; Falk, K.; Moseler, M., Calculating high-pressure PAO4 viscosity with equilibrium molecular dynamics simulations, Tribology letters 72 (2024) Art. 40, 15 pages Link

Codrignani, A. R.; Peeters, S.; Holey, H.; Stief, F.; Savio, D.; Pastewka, L.; Moras, G.; Falk, K.; Moseler, M., Toward a continuum description of lubrication in highly pressurized nanometer-wide constrictions: The importance of accurate slip laws, Science advances 9/48 (2023) Art. eadi264, 17 pages Link

Sauer, F.; Codrignani, A.; Haber, M.; Falk, K.; Mayrhofer, L.; Schwitzke, C.; Moseler, M.; Bauer, H.-J.; Schulze, V., Multiscale simulation approach to predict the penetration depth of oil between chip and tool during orthogonal cutting of AISI 4140, Procedia CIRP 117 (2023) 426-431 Link

Falk, K.; Savio, D.; Moseler, M., Nonempirical free volume viscosity model for alkane lubricants under severe pressures, Physical review letters 124/10 (2020) Art. 105501, 6 pages Link

Savio, D.; Falk, K.; Moseler, M., Slipping domains in water-lubricated microsystems for improved load support, Tribology international 120 (2018) 269-279 Link

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