Saint-Étienne, France
Saint-Étienne, France

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Pop O.,University of Limoges | Dubois F.,University of Limoges | Meite M.,ENISE | Absi J.,University of Limoges
Advanced Materials Research | Year: 2013

In this paper a new formalism based on the complementarity between the optical full field techniques and integral invariant Mtheta is proposed in order to evaluate the fracture parameters in cracked specimen made of wood, under mixed mode loadings. The coupling between the experimental and numerical approaches allows identifying the fracture parameters in terms of energy release rate without any material elastic properties such as the elastic modulus and the Poisson's ratio. The proposed formalism allows also determining, in addition with the fracture parameters, the local elastic properties in terms of reduced elastic compliance. The fracture mixed mode tests are realized using a Single Edge Notch sample made in Douglas with the Arcan fixtures and dried to 11% moisture content and the crack is cutting in Radial-Longitudinal system. © (2013) Trans Tech Publicutions, Switzerland.

Meite M.,ENISE | Dubois F.,University of Limoges | Pop O.,University of Limoges | Absi J.,University of Limoges | Dopeux J.,PFT
WCTE 2014 - World Conference on Timber Engineering, Proceedings | Year: 2014

This paper develops a new method based on a strong coupling between experimental full-fields information of Digital Images Correlation (DIC) and numerical modeling by Finite Element Method (FEM) to analyse in another way, fracture problems in Timber structure subjected to complex loading of mixed-mode in service conditions. To better apprehend wood material fracture behavior, cracked specimens were made of Douglas fir and undergo complex loading in tension for different mixity ratio β (for instance β= 0°,15°,45°,L,90°) involving the crack to be therefore likely under mixed-mode (I+II) loading at the crack tip (Fig.1).

Underwood L.,University of Canterbury | Schumacher J.,TU Darmstadt | Burette-Pommay J.,ENISE | Jermy M.,University of Canterbury
Sports Engineering | Year: 2011

The speed attained by a track cyclist is strongly influenced by aerodynamic drag, being the major retarding force in track events of more than 200 m. The aims of this study were to determine the effect of changes in shoulder and torso angles on the aerodynamic drag and power output of a track cyclist. The drag of three competitive track cyclists was measured in a wind tunnel at 40 kph. Changes in shoulder and torso angles were made using a custom adjustable handlebar setup. The power output was measured for each position using an SRM Power Meter. The power required by each athlete to maintain a specific speed in each position was calculated, which enabled the surplus power in each position to be determined. The results showed that torso angle influenced the drag area and shoulder angle influenced the power output, and that a low torso angle and middle shoulder angle optimised the surplus power. However, the lowest possible torso angle was not always the best position. Although differences between individual riders was seen, there was a strong correlation between torso angle and drag area. © 2011 International Sports Engineering Association.

Bottger P.H.M.,ETH Zurich | Bottger P.H.M.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Gusarov A.V.,ENISE | Shklover V.,ETH Zurich | And 2 more authors.
International Journal of Thermal Sciences | Year: 2014

This study aims at the theoretical examination of the anisotropy of thermal conductivity F = κ||/κ⊥ that could be engineered in hard multilayer coatings, prepared using arc-evaporation. High values of F and thereby high lateral heat dissipation can reduce detrimental thermal gradients that emerge during cutting and friction processes in hard coatings. As coating deposition is widely done using arc-evaporation that leads to inclusion of droplets of different shapes and material in the coating, it is further evaluated to which extent F is be affected by these inclusions. The ideal continuous anisotropic medium with inclusions can be described using the effective medium Maxwell Garnett Approximation (MGA). A deposited multilayer structure presents a particular case with a limited number of layers inducing anisotropy and is simulated using the Finite Element Method (FEM) and compared to the idealized MGA predictions. The results show that the effect of droplets on the anisotropy F is strongly dependent on droplet shape, material and orientation. For spherical droplets at concentrations that are usually observed in arc-evaporation coatings, the value of F decreases linearly, proportional to the droplet concentration and almost independent of droplet thermal conductivity for regularly experimentally encountered droplet materials. When ellipsoidal droplets are considered, F depends strongly on the material and orientation of the droplets. The effects of finite thermal interface resistance between individual layers and around the droplet inclusions are evaluated separately and are found to be generally beneficial. This study shows that creating multilayers with high anisotropy of thermal conductivity should be possible even in the presence of unavoidable droplet inclusions. Furthermore, controlling metal droplet formation upon arc-evaporation of hard coatings can be used as a tool to engineer the anisotropy of thermal conductivity in arc-deposited multilayer coatings. © 2013 Elsevier Masson SAS. All rights reserved.

Thomas M.,ONERA | Malot T.,ENSAM | Aubry P.,CEA Saclay Nuclear Research Center | Colin C.,MINES ParisTech | And 2 more authors.
Materials at High Temperatures | Year: 2016

This paper deals with the prospects for additive manufacturing (AM) of bulk TiAl alloys. A number of AM processes have already been explored in the literature for these intermetallic alloys. The main trend developed in published works concerns a strong crack sensitivity of this relatively brittle material due to rapid successive heating and cooling cycles. Optimised processing conditions have already been achieved for producing sound and crack-free TiAl materials by means of EBM and laser metal deposition processes. This experimental work was particularly focused on the third process, i.e. selective laser melting, to produce fully dense TiAl parts. A series of beads, surface layers and cubes have been manufactured to investigate the microstructural evolution. Post-heat treatments allowed a uniform microstructure to be restored for the intermetallic TiAl alloy. © 2016 Informa UK Limited, trading as Taylor & Francis Group.

Vilaro T.,MINES ParisTech Center of materials | Kottman-Rexerodt V.,ONERA | Thomas M.,ONERA | Colin C.,MINES ParisTech Center of materials | And 7 more authors.
Advanced Materials Research | Year: 2010

A Ti-47Al-2Cr-2Nb (at.%) material was fabricated using two laser-based methods, "Selective Laser Melting" (SLM) and "Direct Metal Deposition" (DMD), for potential uses in aircraft jet engines. Experiments were conducted under controlled atmosphere by changing the processing parameters. Optimal parameters were searched for this relatively low ductility material to prevent cracking due to built-up residual stresses during fast cooling. It was observed that these non-equilibrium cooling conditions were fast enough to generate ultra fine and metastable structures exhibiting high microhardness values. Post heat-treatments were successfully used to restore homogeneous lamellar or duplex microstructures and to relieve the residual stresses. A comparison of these two methods is provided in terms of powder requirements and of process parameters to achieve noncracked structures and fully dense materials. © (2010) Trans Tech Publications.

Attia Y.,Jean Monnet University | Joliveau T.,Jean Monnet University | Favier E.,ENISE
Lecture Notes in Geoinformation and Cartography | Year: 2014

The aim of this chapter is to describe a new method for assigning a geographical position to an urban picture. The method is based only on the content of the picture. The photograph is compared to a sample of geolocated 3D images generated automatically from a virtual model of the terrain and the buildings. The relation between the picture and the images is built through the matching of detected lines in the photograph and in the image. The lines extraction is based on the Hough transform. This matching is followed by a statistical analysis to propose a probable location of the picture with an estimation of accuracy. The chapter presents and discusses the results of an experiment with data about Saint-Etienne, France and ends with proposals for improving and extending the method. © Springer International Publishing Switzerland 2014.

Heuze T.,CNRS Jean Le Rond d'Alembert Institute | Leblond J.-B.,CNRS Jean Le Rond d'Alembert Institute | Bergheau J.-M.,ENISE
Mecanique et Industries | Year: 2011

A numerical tool for the simulation of the Friction Stir Spot Welding process is developed. The model is based on a fluid/solid coupling which describes the state of the material in the structure. The model includes the P1+/P1 finite-element, developed with a strong thermomechanical coupling, both for fluid and solid behaviours. The coupling, associated with an Arbitrary Eulerian Lagrangian approach, is implemented in a new option of the finite element code SYSWELD®. We present here a first simulation of the Friction Stir Spot Welding process. © AFM, EDP Sciences 2011.

Direct numerical solution of the radiation transfer equation is often easier than implementation of its differential approximations with their cumbersome boundary conditions. Nevertheless, these approximations are still used, for example, in theoretical analysis. The existing approach to obtain a differential approximation based on expansion in series of the spherical harmonics is revised and expansion in series of the eigenfunctions of the scattering integral is proposed. A system of eigenfunctions is obtained for an arbitrary phase function, and explicit differential approximations are built up to the third Chapman-Enskog order. The results are tested by its application to the problem of a layer. The third-order Chapman-Enskog approximation is found to match the boundary conditions better than the first-order one and gives considerably more accurate value for the heat flow. The accuracy of the both first-and third-order heat flows generally increases with the optical thickness. In addition, the third-order heat flow tends to the rigorous limit value when the optical thickness tends to zero. © 2011 American Society of Mechanical Engineers.

Gusarov A.V.,ENISE
Journal of Quantitative Spectroscopy and Radiative Transfer | Year: 2013

The multiphase model, where each phase is characterized by its own average radiation intensity, is known to be perspective and useful to take into account the dependent scattering. It has not been applied to statistically anisotropic materials, which is a serious theoretical gap. The system of equations for radiation transfer in layered two-phase systems is derived in the assumption of geometrical optics. No internal scattering in the layers is considered. The obtained model is validated by comparison with the known rigorous solutions for the reflectance/transmittance problem. The results of the model for a single optical window are rigorous in the four limiting cases of small and high internal transmittance and surface reflectivity. The model is not precise but still reasonable at intermediate values of these two parameters. In the case of multiple windows, the initial distribution of the radiative energy between phases has a small impact on the calculated reflectance and transmittance. The variations of the reflectance and transmittance due to the variation of the initial distribution decrease with the number of windows. Chapman-Enskog expansion of the model equations for emitting media gives the generalized Fourier law for radiative heat transfer. Radiative interaction between phases is shown to depend on the specific surface of interfaces. In the case of the same refractive index of the phases and completely transparent interfaces, the radiative thermal conductivity tensor is obtained, and its anisotropy factor is calculated for gray media. © 2012 Elsevier Ltd.

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