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Saint-Étienne, France

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. Source

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. Source

Heuze T.,CNRS Jean Le Rond dAlembert Institute | Leblond J.-B.,CNRS Jean Le Rond dAlembert 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. Source

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. Source

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. Source

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