Programmation robotique en utilisant la méthode de maillage et la simulation thermique du procédé de la projection thermique

L objectif de cette étude est d améliorer l extension du logiciel de programmation hors-ligne RobotStudio existante et de développer une nouvelle stratégie pour générer la trajectoire du robot par rapport aux paramètres essentiels de projection thermique. Notamment, l historique de la température par rapport à la trajectoire générée est prise en compte dans cette étude.L extension logicielle Thermal Spray Toolkit (TST) intégrée dans le cadre de RobotStudio est spécialement développée pour générer la trajectoire du robot en projection thermique. L amélioration de l extension TST dans la nouvelle version de RobotStudio est mise au point sur deux modules principaux :PathKit : génération de la trajectoire sur des pièces complexes.ProfileKit : modélisation du cordon singulier du dépôt et prédiction de son épaisseur en fonction des paramètres opératoires.Les déficiences existantes de l extension TST impliquent de mettre en œuvre une méthode plus avancée qui permettra de générer la trajectoire du robot en utilisant le maillage pour le calcul d élément finis. Ainsi, l opération de projection thermique pourra être menée. Dans cette étude, la méthodologie de maillage est introduite afin de fournir une stratégie de choix de points de trajectoire et l obtention d orientations de ces points de trajectoire sur la surface à revêtir. Un module dit MeshKit est donc ajouté dans l extension TST afin de lui apporter ces fonctionnalités nécessaires.Un couplage entre la trajectoire du robot et la répartition de chaleur du substrat a été développé, ce qui permet d étudier l évolution de température pendent le processus de projection thermique.The objective of this study is to improve the add-in package of off-line programming software RobotStudio and to develop a new strategy for generating the robot trajectory according to the kinematic parameters of thermal spraying. The computed temperature evolution relative to the generated robot trajectory on the coating surface is also considered in this study.The add-in package Thermal Spray Toolkit (TST) integrated in RobotStudio is developed to generate the robot trajectory for thermal spraying. The improved TST for new version of RobotStudio is composed of two principle modules:PathKit: generation of robot trajectory on the free-form coating surface.ProfileKit: modeling the coating profile and prediction the coating thickness based on kinematic parameters.The existing deficiency of TST leads to the development of an advanced robot trajectory generation methodology. In this study, the new approach implements the robotic trajectory planning in an interactive manner between RobotStudio and the finite element analysis software (FES). It allows rearranging the imported node created on the surface of workpiece by FES and in turns generating the thermal spraying needed robot trajectories.A coupling between the robot trajectory and the heat distribution on the substrate has been developed, which allows analyzing the temperature evolution during the thermal spray process, it helps to minimize thermal variations on the substrate and to select the appropriate execution sequence of trajectory.BELFORT-UTBM-SEVENANS (900942101) / SudocSudocFranceF

Minority-spin conduction in ferromagnetic Mn5_5Ge3_3Cx_x and Mn5_5Si3_3Cx_x films derived from anisotropic magnetoresistance and density functional theory

The anisotropic magnetoresistance (AMR) of ferromagnetic Mn$_5$Ge$_3$C$_x$ (0 $\le$ x $\le$ 1) and Mn$_5$Si$_3$C$_x$ (0.5 $\le$ x $\le$ 1) thin films was investigated and compared with density functional theory calculations from which the spin-split electronic density of states at the Fermi level and the spin polarization were obtained. The isostructural compounds exhibit different AMR behavior. While only Mn5Si3C0.5 shows a positive AMR ratio and a positive spin polarization, the negative AMR ratio of all other compounds is due to a negative spin polarization. The correlation between the sign of the AMR and the degree of spin polarization is in agreement with theoretical calculations of the AMR ratio indicating that the magnetoelectronic transport in both compounds is dominated by minority-spin conduction. The dominating role of minority-spin conduction remains unaffected even after incorporation of carbon into the crystalline lattice which weakens both AMR and spin polarization

Phase transitions associated with magnetic-field induced topological orbital momenta in a non-collinear antiferromagnet

Resistivity measurements are widely exploited to uncover electronic excitations and phase transitions in metallic solids. While single crystals are preferably studied to explore crystalline anisotropies, these usually cancel out in polycrystalline materials. Here we show that in polycrystalline Mn3Zn0.5Ge0.5N with non-collinear antiferromagnetic order, changes in the diagonal and, rather unexpected, off-diagonal components of the resistivity tensor occur at low temperatures indicating subtle transitions between magnetic phases of different symmetry. This is supported by neutron scattering and explained within a phenomenological model which suggests that the phase transitions in magnetic field are associated with field induced topological orbital momenta. The fact that we observe transitions between spin phases in a polycrystal, where effects of crystalline anisotropy are cancelled suggests that they are only controlled by exchange interactions. The observation of an off-diagonal resistivity extends the possibilities for realising antiferromagnetic spintronics with polycrystalline materials.Comment: 4 figures, 1 tabl

Neutron powder-diffraction study of phase transitions in strontium-doped bismuth ferrite: 1. Variation with chemical composition

We report results from a study of the crystal structure of strontium-doped BiFeO3 using neutron powder diffraction and the Rietveld method. Measurements were obtained over a wide range of temperatures from 300–800 K for compositions between 10–16% replacement of bismuth by strontium. The results show a clear variation of the two main structural deformations – symmetry-breaking rotations of the FeO6 octahedra and polar ionic displacements that give ferroelectricity – with chemical composition, but relatively little variation with temperature. On the other hand, the antiferromagnetic order shows a variation with temperature and a second order phase transition consistent with the classical Heisenberg model. There is, however, very little variation in the behaviour of the antiferromagnetism with chemical composition, and hence with the degree of the structural symmetry-breaking distortions. We therefore conclude that there is no significant coupling between antiferromagnetism and ferroelectricity in Sr-doped BiFeO3 and, by extension, in pure BiFeO3

ATP Binding and Channel Activation in P2X Receptors

Purinergic P2X receptors are a family of nonselective cation channels gated by extracellular adenosine 5′-triphosphate. They are important drug targets primarily because of their involvement in neuropathic pain and inflammation. ATP binds allows Na+ and Ca2+ to pass through the channel pore, thus causing membrane depolarization and affecting various downstream Ca2+-dependent signaling processes. A concerted effort by investigators over the last two decades has culminated in significant advances in our understanding of where ATP binds and how ATP binding leads to channel opening and ion flux. The recent publication of the crystal structures for both the closed and open channel conformations of the zebrafish P2X4 receptor sheds new light on how P2X receptors work. In this review, we will attempt to present the existing functional data regarding ATP binding with the available crystal structure data and different experimental approaches that have been used to explore the ATP-binding sites

Programmation robotique hors-ligne et contrôle en temps réel des trajectoires (développement d une extension logicielle de "Robotstudio" pour la projection thermique )

Cette étude s inscrit dans le cadre de l amélioration et de la maîtrise de l utilisation d un robot appliquée à la projection thermique sur des formes de géométrie complexe. Différentes voies ont été étudiées pour mener à bien ce projet. Sur la base d une structure logicielle dénommée (RobotStudio ), une trousse à outil dédiée à la projection thermique dite Thermal Spray Toolkit a été développée. Cette trousse à outil comporte trois modules ( PathKit , MonitorKit , ProfileKit ) qui fournissent respectivement les créations de la trajectoire robot, le contrôle du robot en ligne et l analyse du profil du dépôt dans un environnement de projection thermique. Dans un premier temps, les principes de l extension logicielle pour RobotStudio ont été étudiés et la structure globale du programme d extension a été établie. Puis, des méthodes et protocoles de communication ont été analysés et testés pour la connexion avec le robot. Plusieurs expérimentations ont été effectuées pour tester les fonctionnalités et la stabilité du logiciel développé. Les résultats présentés montrent que ce développement est bien adapté à la génération et l optimisation de trajectoires robot hors-ligne pour la projection thermique.The aim of this study was to improve robot trajectories control during the thermal spraying process on complex geometric objects. Many researches have been done to support this project. A commercial software (RobotStudio ) has been installed and the robot off-line programming has been tested and achieved. A toolkit dedicated to thermal spray called Thermal Toolkit Spray was developed on the platform RobotStudio . This toolkit consists of three modules ( PathKit , MonitorKit , ProfileKit ) which respectively provide the generation of the robot trajectory, the real-time monitoring of the robot and the analysis of the profile of the deposit.Initially, the principles of the add-in program for RobotStudio were studied and the structure of the software was established. Then, the methods and communication protocols were analyzed and tested for the connection with the robot. Several experiments were carried out to test the software functions and its stability. The results show that this development can perfectly be used to create, optimize and monitor the robot program in the whole process of thermal spraying.BELFORT-BU L. FEBVRE (900102102) / SudocBELFORT-UTBM-SEVENANS (900942101) / SudocSudocFranceF

Physical Deposition Profile Based Toolpath Generation and Optimization for Additive Volume Building in Hybrid Additive Manufacturing

In hybrid additive manufacturing (HAM), toolpaths affect the volume building and removing during the sequential or iterative hybrid processing since they control the deposition nozzle or cutting tools. In sequential hybrid additive manufacturing, toolpaths for additive manufacturing module define the volume directly determines of the shape accuracy and volume building time. In this paper, we report a new toolpath generation and optimization method for a developing cold spraying - based HAM process’s additive processing module. This method adopts a valid physical deposition profile to set scanning parameters and then applies an evolutionary optimization algorithm to minimize the total scanning length for building a set of ordered disconnected volumes on a predefined base. The propose method is illustrated by a complex tree shape model and validated by three selected numerical examples. It has potential to help save spraying raw materials and time as well as improve shape accuracy.Mechanical Engineerin