Publications associées à The Role of Geometrical Parameters in the Lubrication of the Swiss Lever Escapement

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

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

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

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

A Simple Mechanistic Model for Friction of Rough Partially Lubricated Surfaces

Jean-François Molinari, Julie Richard, 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

Stability and Unbalance Analysis of Rigid Rotors Supported by Spiral Groove Bearings: Comparison of Different Approaches

Jürg Alexander Schiffmann, Elia Iseli

The dynamic behavior of spiral-grooved gas bearing supported four degrees-of-freedom (DOF) rotors is investigated by means of linearized bearing force coefficients and full time-integrated transient analysis. The transient method consists of a state-space ...

2021

A lubricated tribocorrosion model incorporating surface roughness

Stefano Mischler, Shoufan Cao

This study presents an improvement of an existing tribocorrosion model developed for passive CoCrMo alloys. This model is based on an empirical formalism established by Duncan Dowson in his pioneering works on the relation between wear and elasto-hydrodyna ...

2021

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 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

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

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

Flexure Pivot Oscillators for Mechanical Watches

Etienne Frédéric Gabriel Thalmann

It appears that the concerted efforts of the watchmaking industry are leading towards a limit in mechanical watch accuracy. The general consensus in horology is that the time base's quality factor, a dimensionless number that characterizes the oscillator d ...

EPFL2020

Flexure Pivot Oscillator With Intrinsically Tuned Isochronism

Simon Nessim Henein, Mohammad Hussein Kahrobaiyan, Etienne Frédéric Gabriel Thalmann, Ilan Vardi

The most important property for accurate mechanical time bases is isochronism: the independence of period from oscillation amplitude. This paper develops a new concept in isochronism adjustment for flexure-based watch oscillators. Flexure pivot oscillators ...

2020

Parametric analysis of the elastohydrodynamic lubrication efficiency on induced seismicity

Marie Estelle Solange Violay, Chiara Cornelio

During reservoir stimulations, the injection of fluids with variable viscosities can trigger seismicity. Several fault lubrication mechanisms have been invoked to explain the dynamic stress drop occurring during those seismic events. Here, we perform a par ...

2020

Pressure Profile Measurements within The Gas Film of Journal Foil Bearings Using An Instrumented Rotor with Telemetry

Jürg Alexander Schiffmann, Karim Magdi Zakaria Abdelrahman Shalash

Foil bearings are strong candidates to support oil-free turbomachinery. Although foil bearings are a widely used technology, models describing their behavior are not validated using the film pressure, which is the fundamental variable of any fluid film bea ...

2020

Effect of Fluid Viscosity on Earthquake Nucleation

Marie Estelle Solange Violay, Chiara Cornelio

Injection of fluids in geo-reservoirs can reduce the effective stresses at depth, lubricating the nearby faults, promoting slip and, potentially, earthquakes. High-viscous fluids are often used during hydraulic fracturing and production phases in geo-reser ...

2020

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

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

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

Propagation of fluid driven fractures in transversely isotropic material

Fatima-Ezzahra Moukhtari

The propagation of fluid driven fractures is used in a number of industrial applications (well stimulation of unconventional reservoirs, development of deep geothermal systems) but also occurs naturally (magmatic dyke intrusion). While the mechanics of hyd ...

EPFL2020

Flexible support and enhanced groove geometries for gas lubricated bearings

Philipp Kaspar Bättig

Gas lubricated Herringbone-Grooved Journal Bearings (HGJB) are a promising solution to support high-speed rotors in oil-free turbo-machinery due to their compactness, relatively low losses, no need for lubrication and low wear. Gas lubricated bearings, how ...

EPFL2019

Thin Gas Film Isothermal Condensation in Aerodynamic Bearings

Jürg Alexander Schiffmann, Eliott Philippe Guenat

High-speed small-scale turbomachinery for waste heat recovery and vapor compression cycles is typically supported on gas-lubricated bearings operating close to the saturation conditions of the lubricant. Under particular conditions, the gas film might loca ...

2019