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Concept

Lubrication

Related publications (26)

Computational fluid dynamics simulations of the heat transfer properties of graphene-based nanolubricants and application to hydrodynamic lubrication

Roberto Guarino

In this paper, we consider experimental data available for graphene-based nanolubricants to evaluate their convective heat transfer performance by means of computational fluid dynamics (CFD) simulations. Single-phase models with temperature-dependent prope ...

Aip Publishing2024

Fault roughness controls injection-induced seismicity

Lei Wang, Simon Guérin-Marthe

Surface roughness ubiquitously prevails in natural faults across various length scales. Despite extensive studies highlighting the important role of fault geometry in the dynamics of tectonic earthquakes, whether and how fault roughness affects fluid-induc ...

National Academy of Sciences2024

Influence of Viscous Lubricant on Nucleation and Propagation of Frictional Ruptures

Marie Estelle Solange Violay, François Xavier Thibault Passelègue, Federica Paglialunga

Fluids are pervasive in the Earth's crust and saturate fractures and faults. The combination of fluids and gouge layers developing along faults can generate fluids of different viscosities. Such viscous fluids were found to influence the reactivation, fric ...

2023

Thermal management for gas lubricated, high-speed turbomachinery

Jürg Alexander Schiffmann, Wei Liu, Luis Eric Olmedo Ocampo, Wanhui Liu

High-speed turbomachinery is commonly designed to achieve high power densities. Limited space for active cooling results in a challenging thermal management. A thermal modeling approach leveraging modern declarative programming capabilities is presented, y ...

2023

Modeling the origins of adhesive wear across scales

Son-Jonathan Pham-Ba

Friction and wear occur at every interface between solid materials. In the design of mechanical devices, it is desirable to be able to quantify and control the amount of friction and wear, as well as predict their evolution with time. ``Tribology'' is the ...

EPFL2022

The Role of Geometrical Parameters in the Lubrication of the Swiss Lever Escapement

Stefano Mischler, Alejandro Roda Buch, Sandra Guadalupe Maldonado

The lubrication regimes of a contact pair escapement-ruby pallet of a Swiss lever escapement have been investigated combining the theory of fluid lubrication with a well-established kinematic and inverse dynamic multibody model. The kinematic analytical re ...

2021

A Simple Mechanistic Model for Friction of Rough Partially Lubricated Surfaces

Jean-François Molinari, Tobias Brink, Gianluca Costagliola

We report experimental measurements of friction between an aluminum alloy sliding over steel with various lubricant densities. Using the topography scans of the surfaces as input, we calculate the real contact area using the boundary element method and the ...

2021

Experimental Investigation of a Small-Scale Organic Rankine Cycle Turbo-Generator Supported on Gas-Lubricated Bearings

Jürg Alexander Schiffmann, Kévin Rosset

Waste heat recovery (WHR) is expected to contribute to reducing CO2 emissions from trucks. Organic Rankine cycle (ORC) systems show the highest potential for this application, but still lack efficient small-scale expansion devices, in practice. A novel tur ...

2021

A parameter-free mechanistic model of the adhesive wear process of rough surfaces in sliding contact

Jean-François Molinari, Tobias Brink, Lucas Henri Galilée Frérot

In order to develop predictive wear laws, relevant material parameters and their influence on the wear rate need to be identified. Despite decades of research, there is no agreement on the mathematical form of wear equations and even the simplest models, s ...

2021

Onset of sliding across scales: How the contact topography impacts frictional strength

Jean-François Molinari, Ramin Aghababaei, Fabian Barras

When two solids start rubbing together, frictional sliding initiates in the wake of slip fronts propagating along their surfaces in contact. This macroscopic rupture dynamics can be successfully mapped on the elastodynamics of a moving shear crack. However ...

AMER PHYSICAL SOC2021

Nonlinear study on a rigid rotor supported by herringbone grooved gas bearings: Theory and validation

Jürg Alexander Schiffmann, Patrick Hubert Wagner, Philipp Kaspar Bättig, Wanhui Liu

The nonlinear behavior of a rigid rotor supported by herringbone grooved journal gas bearings (HGJBs) was investigated in this study. The two-dimensional narrow groove theory (2D-NGT) was adopted to model the HGJBs. A set of integrated rotor-bearing state ...

2021

Adhesive wear regimes on rough surfaces and interaction of micro-contacts

Jean-François Molinari, Son-Jonathan Pham-Ba

We develop an analytical model of adhesive wear between two unlubricated rough surfaces, forming micro-contacts under normal load. The model is based on an energy balance and a crack initiation criteria. We apply the model to the problem of self-affine rou ...

2021

Tribological properties of gold matrix composite coatings with carbon nanocapsules containing ionic liquid lubricants

Stefano Mischler, Anna Neus Igual Muñoz

Self-lubricating, gold matrix composite coatings were produced by electrochemical codeposition of carbon nanocapsules filled with ionic liquid (IL) from a colloidal galvanic bath on a nickel electrode. The tribological response of the composite coatings wa ...

ELSEVIER2020

Instability of a thin viscous film flowing under an inclined substrate: steady patterns

François Gallaire, Gioele Mariano Nicolò Balestra, Pier Giuseppe Ledda, Gaëtan Pierre Clément Lerisson

The flow of a thin film coating the underside of an inclined substrate is studied. We measure experimentally spatial growth rates and compare them to the linear stability analysis of a flat film modelled by the lubrication equation. When forced by a statio ...

Cambridge University Press2020

Tribological Approach to the Watch Movements

Valentine Agnès Madeleine Magnin

Mechanical watches are complex and sensitive systems that have to maintain a faultless precision over their lifetime. However, this precision can be altered by disturbances occurring during the functioning time, such as friction, lubricant drying, or wear, ...

EPFL2020

Extended Windage Loss Models for Gas Bearing Supported Spindles Operated in Dense Gases

Jürg Alexander Schiffmann, Kévin Rosset

Generic models are proposed to evaluate the skin friction coefficient acting on enclosed rotating disks and cylinders under various flow regimes. In particular, a model taking into account the inner radius of the disk is developed. The models are compared ...

2020

An Instrumented High-Speed Rotor with Embedded Telemetry for The Continuous Spatial Pressure Profile Measurement in Gas Lubricated Bearings: A Proof of Concept

Jürg Alexander Schiffmann, Karim Magdi Zakaria Abdelrahman Shalash

Pressure is one of the constitutional quantities governing the flow field in gas lubricated bearings. Knowledge of the pressure is of principal importance in the fundamental understanding of such bearings and for the calibration of reduced order models. Th ...

2020

Tribocorrosion of a CoCrMo alloy in sulfuric acid - Glycerol mixtures

Stefano Mischler, Shoufan Cao

This work reports on the tribocorrosion properties of a CoCrMo alloy sliding under imposed passive potential against alumina in sulfuric acid-glycerol mixtures exhibiting different viscosities and thus, in principle, lubrication properties. As expected, we ...

ELSEVIER SCIENCE SA2020

A Review of Grooved Dynamic Gas Bearings

Jürg Alexander Schiffmann, Eliott Philippe Guenat, Lili Gu

This paper offers an extensive review of publications dealing with the modeling, the design and the experimental investigation of grooved dynamic gas lubricated bearings. Recent years have witnessed a rise in small-scale and high-speed turbomachinery appli ...

2020

Advanced design methods and non-ideal gas lubrication applied to aerodynamic bearings

Eliott Philippe Guenat

Clean and energy-efficient turbomachinery are playing an increasingly important role in the decarbonization of heating systems, waste heat recovery and transportation, as the use of small-scale heat pumping and fuel cells spreads. Such machines typically e ...

EPFL2020