Applied electrotribology R&D for your company

Electrotribology: analysis method and programmable friction

The "Sustainable Lubricants and Tribochemistry" team at Fraunhofer IWM is dedicated to the development of innovative approaches in tribology, with a particular focus on the field of electrotribology. This interdisciplinary approach combines electrical engineering and tribology for the optimization and analysis of tribosystems.

What is electrotribology?

Electrotribology studies the interactions between moving surfaces and a lubricant under the influence of electric current or potential. This discipline is of crucial importance for industries such as electric mobility and wind turbines, where electric fields can influence the effectiveness of lubricants.

Our research fields include:

• Electrochemical analyses: We use electrical currents or voltages to investigate the processes of corrosion and the interactions between lubricants and surfaces. On this basis, we identify additives that meet the specific requirements of different applications.
• Targeted improvement of tribological properties: Through the targeted application of electrical currents or voltages, we optimize tribological systems to improve friction and wear behaviour. This includes increasing performance and efficiency through improved interactions between lubricants, additives and surfaces.
• Investigation of current as a cause of damage: we investigate the effects of parasitic electrical currents on tribological systems and identify mechanisms such as electrical breakdown in rolling bearings. Our aim is to minimize damage and increase the reliability of machines and components through targeted additives and innovative solutions.

Electrotribology R&D services for your company

Tribological standard tests

• Combination of electrochemical methods with tribological tests in order to carry out electro-tribological investigations on common model test systems (e.g. pin-disk, ball-plate) during rotation or oscillation.
• Specification of electrical voltages or currents with a potentiostat
• Electrically insulated test benches

Tribological component testing and system analysis

• Measurement of breakdown stress in plain and roller bearings
• Targeted influencing of the tribological behavior in plain bearings by specifying electrical voltages
• Comparisons with the state of the art technology
• Service life assessment

Damage and material analysis

• Electrotribological surface damage (including electropitting)
• High-resolution surface analysis (SEM-EDX, XPS)
• Lubricant decomposition (IR spectroscopy, rheology)
• Corrosion (including current-voltage curves, cyclovoltammetry, electrochemical impedance spectroscopy (Enabling Innovation))

Development of testing techniques

• Adaptation of electrotribological measurements to customer-specific load and test geometries
• Application-oriented electrotribological characterization in rolling and plain bearings

Development of tribosystems and material substitution

• Development of electrically conductive model lubricants
• Electrochemical and electrotribological testing of a wide range of materials (polymers, metals, ceramics) and lubricants
• Identification of suitable additives by investigating the tribological mechanisms

Programmable friction

The "Programmable Friction" research cluster is investigating the control of friction using external triggers in order to autonomously set the optimum friction value during the operation of a clutch or bearing, for example. In contrast to the one-off adjustment of the lubricant, this offers enormous advantages for the efficiency and service life of applications. Our aim is to program friction systems in such a way that they are operated in the optimum tribological state across the entire range of application parameters.

Particular attention is paid to novel approaches that make it possible to control friction properties using optical or electrostatic stimuli. These external switches specifically influence the interface chemistry and make it possible to dynamically adjust friction coefficients and positioning.

example, our research on electrically programmable friction is based on the use of ionic liquids that specifically change friction by electrically polarizing the friction surfaces. Another approach is to control friction via optically switchable lubricants and surfaces by using light as a trigger. By developing such innovative solutions, we are helping to improve the performance and efficiency of mechanical systems.

Website:

Fraunhofer cluster of excellence Programmable Materials CPM, Programmable Friction

Electrotribological characterization of e-fluids and lubricating greases 

E-fluids and lubricating greases are essential in modern electric drives: they lubricate gears and bearings and cool the electric motor. In high-voltage environments, they protect against corrosion and short circuits. A key problem is the build-up of electrical charges, which can lead to breakdowns and damage.

Our innovative method for the electrotribological characterization of lubricants enables us to precisely analyse the breakdown stress in rolling bearings. We have found that lower lubricant temperatures reduce the breakdown voltage. A higher viscosity at cooler temperatures increases the lubricant film thickness and increases the electrical resistance, which delays the breakdown.

The aim is to investigate the electro-tribological properties of various lubricants and to correlate their electrical conductivity and viscosity. In this way, we lay the foundation for the development of e-fluids and lubricating greases with optimized tribological and electrochemical properties - for reliable performance of your electric drives.

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Electrotribology publications

• Lubricants | Free Full-Text | Investigation of Programmable Friction with Ionic Liquid Mixtures at the Nano- and Macroscales (mdpi.com)
• Tribological performance of electrically conductive and self-lubricating polypropylene–ionic-liquid composites - RSC Advances (RSC Publishing) DOI:10.1039/D3RA00712J
• Towards programmable friction: control of lubrication with ionic liquid mixtures by automated electrical regulation | Scientific Reports (nature.com)
• Galvanically induced potentials to enable minimal tribochemical wear of stainless steel lubricated with sodium chloride and ionic liquid aqueous solution | Friction (springer.com)
• Influence of electric potentials on the tribological behaviour of silicon carbide - ScienceDirect
• Influence of Electrochemical Potentials on the Tribological Behavior of Silicon Carbide and Diamond-Coated Silicon Carbide | Journal of Bio- and Tribo-Corrosion (springer.com)
• Influence of electric potentials on friction of sliding contacts lubricated by an ionic liquid - Physical Chemistry Chemical Physics (RSC Publishing) DOI:10.1039/C4CP05965D

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