Les Artigues-de-Lussac, France
Les Artigues-de-Lussac, France

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Bernard B.,CEA Le Ripault | Bianchi L.,CEA Le Ripault | Malie A.,SNECMA | Joulia A.,Safran | Remy B.,LEMTA
Journal of the European Ceramic Society | Year: 2016

Suspension plasma spraying (SPS) is used to perform enhanced YSZ coating with columnar microstructure for thermal barrier coating (TBC) applications. By combination of plasma flow, substrate preparation, suspension formulation and injection or coating kinematic management it is possible to tune SPS coating structure from widely-separated columns to a significantly more compact columnar structure. Among these parameters, substrate roughness control, combined with an adapted coating growth velocity, are identified as the most relevant. An analytical approach is presented to describe columns growth based on coating image analysis. It allows to give the expression of the lateral and normal growth speeds responsible of the columnar structure. © 2015 Elsevier Ltd.

Meraghni F.,Arts et Metiers ParisTech | Nouri H.,Arts et Metiers ParisTech | Bourgeois N.,LEM3 | Czarnota C.,LEMTA | Lory P.,Renault S.A.
Procedia Engineering | Year: 2011

The work deals with the parameters identification and the experimental validation of a phenomenological model for fatigue anisotropic damage in short glass fiber reinforced polyamide (PA6-GF30). The damage fatigue model has been formulated in terms of strain energy and was implemented into the finite element code ABAQUS/Standard through a user defined material subroutine UMAT. The present paper focuses mainly on the identification strategy based on homogeneous and heterogeneous fatigue tests. Damage parameters governing longitudinal and transversal damage (dLL and dTT) are identified from homogeneous tension-tension fatigue tests performed in both material directions. The damage parameters governing the shear induced damage (dLT) are identified using heterogeneous fatigue tests carried out on a specific configuration. This heterogeneous fatigue test gives rise to non-uniform distributions of the in-plane strain components: εLL, εTT and εLT. Heterogeneous strain fields are measured by the digital image correlation technique (DIC) during the fatigue test. The in-plane strain components are coupled to numerical computations through an inverse method to determine the parameters set governing the shear induced damage. The comparison between the damage model predictions and the damage curves obtained from fatigue tests shows a good agreement in both material directions. © 2011 Published by Elsevier Ltd.

Cesard V.,INRS | Cesard V.,Institute for Radiological Protection and Nuclear Safety | Belut E.,INRS | Prevost C.,Institute for Radiological Protection and Nuclear Safety | And 2 more authors.
Annals of Occupational Hygiene | Year: 2013

The intention of this article is to compare the containment performance of a Type II microbiological safety cabinet (MSC) confronted with the simultaneous generation of a saline nanoparticle aerosol and a tracer gas (SF6). The back dissemination coefficient, defined as the ratio of the pollutant concentration measured outside the enclosure to the pollutant flow rate emitted inside the enclosure, is calculated in order to quantify the level of protection of each airborne contaminant tested for three enclosure operating configurations: an initial configuration (without perturbations), a configuration exposing a dummy in front of the enclosure (simulation of an operator), and a configuration employing the movement of a plate in front of the enclosure (simulation of human movement). Based on the results of this study, we observed that nanoparticulate and gaseous behaviours are strongly correlated, thus showing the predominance of air-driven transport over particle-specific behaviour. The average level of protection afforded by the MSC was found systematically slightly higher for the nanoaerosol than for the gas in the studied configurations (emission properties of the source, operating conditions, and measurement protocols). This improved protection efficiency, however, cannot be considered as a warrant of protection for operators since operating condition and ventilation parameters are still more influential on the containment than the pollutant nature (i.e. nanoaerosol or gas). © 2012 The Author 2012. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.

Jamali-Zghal N.,Ecole des Mines de Nantes | Amponsah N.Y.,University of Florida | Lacarriere B.,Ecole des Mines de Nantes | Le Corre O.,Ecole des Mines de Nantes | Feidt M.,LEMTA
Journal of Cleaner Production | Year: 2013

The aim of this paper is to study via environmental indicators to which extent, replacing fossil fuel with biomass for heating is an environmentally friendly solution. The environmental impact of using biomass depends mostly on the transportation process. Authors define the notion of maximum supply distance, beyond which biomass transportation becomes too environmentally intensive compared to a fossil fuel fired heating system. In this work a carbon footprint analysis and an emergy evaluation, has been chosen to study the substitution of wood for natural gas. The comparative study seeks to examine, via the two approaches, two heating systems: one is fired with wood, transported by trucks and the other one is fired with natural gas transported by pipelines. The results are expressed in terms of maximum supply distance of wood. In the emergy evaluation it represents the maximum supply distance permitting wood to be more emergy saving than natural gas. In the carbon footprint analysis, it represents the maximum supply distance permitting wood to be a carbon saving alternative to natural gas. Furthermore, the unification of carbon footprint and emergy evaluation permits to define, for both approaches, the minimumtheoretical wood burner first law efficiency that allows, CO2 or emergy to be saved, when there is no wood transport. In order to identify the impacts of the main parameters of the study a sensitivity analysis has been carried out. The case study investigated in thispaper showsthat there is a large gapbetween the results.Themaximum supply distances calculated via carbon footprint and emergy evaluation are about 5000 km and 1000 km, respectively, anthe minimum theoretical wood burner efficiencies are about 5% and 54%, respectively. © 2012 Elsevier Ltd. All rights reserved.

Ganghoffer J.-F.,LEMTA
International Journal of Engineering Science | Year: 2012

The surface growth of biological tissues is presently analyzed at the continuum scale of tissue elements, adopting the framework of the thermodynamics of surfaces. Growth is assumed to occur in a moving referential configuration (called the natural configuration), considered as an open evolving domain exchanging mass, work, and nutrients with its environment. The growing surface is endowed with a superficial excess concentration of moles, which is ruled by an appropriate kinetic equation. From a thermodynamic framework of surface growth, the equilibrium equations are derived in material format from a suitable thermodynamic potential, highlighting the material surface forces for growth based on a surface Eshelby stress. Those forces depend upon a surface Eshelby stress, the curvature tensor of the growing surface, the gradient of the chemical potential of nutrients, and a surface force field. Application of the developed formalism to bone external remodeling highlights the interplay between transport phenomena and generation of surface mechanical forces. The model is able to describe both bone growth and resorption, according to the respective magnitude of the chemical and mechanical contributions to the material surface driving force for growth. © 2011 Elsevier Ltd. All rights reserved.

Ganghoffer J.-F.,LEMTA
Journal of the Mechanics and Physics of Solids | Year: 2010

The growth of biological tissues is here described at the continuum scale of tissue elements. Relying on a previous work in Ganghoffer and Haussy (2005), the rephrasing of the balance laws for tissue elements under growth in terms of suitable Eshelby tensors is done in the present contribution, considering successively volumetric and surface growth. Balance laws for volumetric growth are written in both compatible and incompatible configurations, highlighting the material forces for growth associated to Eshelby tensors. Evolution laws for growth are written from the expression of the local dissipation in terms of a relation linking the growth velocity gradient to a growth-like Eshelby stress, in the spirit of configurational mechanics. Surface growth is next envisaged in terms of phenomena taking place in a varying reference configuration, relying on the setting up of a surface potential depending upon the surface transformation gradient and to the normal to the growing surface. The balance laws resulting from the stationnarity of the potential energy are expressed, involving surface Eshelby tensors associated to growth. Simulations of surface growth in both cases of fixed and moving generating surfaces evidence the interplay between diffusion of nutrients and the mechanical driving forces for growth. © 2010 Elsevier Ltd. All rights reserved.

Bluman G.,Mathematics Building | Ganghoffer J.F.,LEMTA
Archives of Mechanics | Year: 2011

NONLOCALLY RELATED SYSTEMS for the Euler and Lagrange systems of two-dimensional dynamical nonlinear elasticity are constructed. Using the continuity equation, i.e., conservation of mass of the Euler system to represent the density and Eulerian velocity components as the curl of a potential vector, one obtains the Euler potential system that is nonlocally related to the Euler system. It is shown that the Euler potential system also serves as a potential system of the Lagrange system. As a consequence, a direct connection is established between the Euler and Lagrange systems within a tree of nonlocally related systems. This extends the known situation for one-dimensional dynamical nonlinear elasticity to two spatial dimensions. © 2011 by IPPT PAN.

Ganghoffer J.-F.,LEMTA
International Journal of Engineering Science | Year: 2010

The connections between the notion of Eshelby tensor and the variation of Hamiltonian like action integrals are investigated, in connection with the thermodynamics of continuous open bodies exchanging mass, heat and work with their surrounding. Considering first a homogeneous representative volume element (RVE), it is shown that a possible choice of the Lagrangian density is the material derivative of a suitable thermodynamic potential. The Euler equations of the so built action integral are the state laws written in rate form. As the consequence of the optimality conditions of the resulting Jacobi action, the vanishing of the surface contribution resulting from the general variation of this Hamiltonian action leads to the well-known Gibbs-Duhem condition. A general three-field variational principle describing the equilibrium of heterogeneous systems is next written, based on the zero potential, the stationarity of which delivers a balance law for a generalized Eshelby tensor in a thermodynamic context. Adopting the rate of the grand potential as the lagrangian density, a generalized Gibbs-Duhem condition is obtained as the transversality condition of the thermodynamic action integral, considering a solid body with a movable boundary. The stationnarity condition of the surface part of the thermodynamic action traduces a relationship between the virtual work of the field variables and the virtual work of the material forces at the moving boundary. This framework is applied to the volumetric growth of spherical tissue elements due to the diffusion of nutrients, whereby a growth model relating the growth velocity gradient to a growth like Eshelby stress built from the grand potential is set up. © 2010 Elsevier Ltd. All rights reserved.

Fiers B.,LEMTA | Ferschneider G.,French Institute of Petroleum | Maillet D.,LEMTA
International Journal of Heat and Mass Transfer | Year: 2010

This paper is devoted to modelling of the thermal interface condition between a solid wall and a granular porous bed through which a fluid flows. Far from the wall, the porous medium, a bed of monodisperse glass beads, is homogeneous. An average enthalpic temperature, based on spatial averaging of the local field over a representative elementary volume, is defined, and a corresponding heat equation can be derived: it uses a Darcy velocity, dispersion coefficients that depend on this velocity, and two volumetric heat capacities (fluid and solid). The presence of a solid wall modifies the local arrangement of the beads, with a porosity that varies with the distance to the wall. In a plug flow situation in the core of the bed, the local velocity becomes larger in the near-wall region, creating a channelling effect that affects the wall-to-porous medium heat transfer. This transfer is studied, for transient wall heating, using heat transfer models of increased complexity and specific analytical methods. Finally a reduced model is proposed for this channelling effect, with its advection component that modifies heat transfer between wall and core region in a way that cannot be modelled by a single heat transfer coefficient. © 2010 Elsevier Ltd. All rights reserved.

Ganghoffer J.-F.,LEMTA
Mechanics Research Communications | Year: 2011

Surface growth is presently described as the motion of a moving interface of vanishing thickness, physically representing the generating cells, separating a zone not yet affected by growth from a domain in which growth has occurred. The jump conditions of density, velocity, momentum, energy, and entropy over the moving front are expressed from the general balance laws of open systems in both physical and material format. The writing of the jump of the internal entropy production in material format allows the identification of a driving force for surface growth, thermodynamically conjugated to the material velocity of the moving front. © 2011 Elsevier Ltd. All rights reserved.

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