Dans une opération de mise en forme, les propriétés volumiques des matériaux ne sont pas les seules garantes de la réussite du procédé. Les aspects surfaciques, en lien notamment avec les propriétés tribologiques des corps en contact (tôle, lubrifiant, outils) se révèlent tout aussi importants. Il convient en ce sens de maîtriser et optimiser autant que faire se peut les conditions de contact lors d’un glissement entre la tôle et l’outillage afin d’assurer la réussite de l’opération de formage.Ces travaux de thèse portent sur la caractérisation d’une solution alternative de lubrification, nommée AFULudine, par fonctionnalisation de surface à base de molécules organiques ; solution ayant pour ambition de se substituer aux huiles minérales chlorées, performantes dans le travail des aciers inoxydables mais particulièrement nocives pour l’environnement et difficiles d’application.Les caractérisations physico-chimiques de surface (IR, électrochimie, MEB) montrent le greffage effectif d’une couche de molécules chimisorbées en surface de l’oxyde métallique, avec une cinétique de l’ordre de quelques secondes. Celle-ci est recouverte d’amas cristallisés et formés en un second temps pendant la phase d’évaporation du solvant. Des analyses morphologiques des cristaux sont réalisées montrant que leur densité et leur structure sont intimement liées au bon comportement tribologique de la surface fonctionnalisée.Le comportement tribologique des tôles (substrat en acier inoxydable ferritique K41 – 1.4509) ainsi traitées a été investigué à la fois grâce à un tribomètre d’étirage-plan permettant de découpler les influences de différentes conditions de sollicitations, telles que la pression de contact, la montée en température des outils ou encore l’influence de la déformation plastique à coeur du matériau, mais aussi en conditions réelles, à l’aide d’une presse d’emboutissage semi-industrielle. De manière plus fondamentale, la formation et la stabilité du tribofilm créé à l’interface a été analysé par l’utilisation d’un micro-tribomètre linéaire en géométrie sphère/plan couplé à de la microscopie électronique et des analyses EDS. / During forming processes, bulk properties of material are not the only guarantee in a process achievement. Surfacicalaspects, mainly coupled with tribological properties of bodies in contact (metal sheet, lubricant, tool) prove to be alsosignificant. It is therefore necessary to control and optimize the contact conditions during a sheet/tool sliding in order toguarantee the success of a forming process.The present work concerns a green lubricant solution characterization, named AFULudine, produced by thefunctionalization of the metallic surface with organic molecules. This solution was developed in substitution to the usualmineral oils, effective in stainless steel stamping but deterious for environment.Physicochemical surface characterization (IR, electrochemistry, SEM) show that the grafting of chemisorbed molecules ontothe surface occures in few seconds. This layer is covered by physisorbed and crystallised species which appear during thesolvent evaporation time. Morphological analyses of these crystals show that both density and structure determine thetribological behavior of the functionalized surface.Sheets tribological behavior (stainless steel ferritic grade, 1.4509 - K41) after treatment, has been investigated thanks to astrip drawing tribometer, allowing to dissociate the influence of various sollicitations conditions (such as contact pressure,tools temperature or plastic deformation of the material) and on an industrial scale with an Erichsen press. Fundamentally,tribo-layerʹs formation and stability have been analysed with the use of a linear micro-tribometer (ball on plane type)coupled with electronic microscopy and EDS analyses.

<p>A battery assembly experiences both mechanical and thermal loadings during its operation. It is critical to perform the thermomechanical analysis to propose a novel design for the highest efficiency.In this study,two main goals include mechanical characterization and deformation responses for a battery cell and assembly, as well as air-cooled concepts design and analysis.Initially, the cell dimensions were measured by cell-sectioning method, and then the mechanical properties were empirically measured by both 3-point flexural, and nanoindentation experiments. Moreover, three pairs of experiments and simulations were conducted to study mechanical behaviors on both a single cell and a battery assembly. They include (1) point-force loading for single, open cell; (2) internal pressurization for single, sealed cell; and (3) internal pressurization for battery assembly.Additionally, both parametric and experimental studies were executed to design, analyze,and validate air-cooled concepts based on the idea of microchannel heatsink. The proposed concepts have the features, which are integrated into the battery cell for generating the cooling channels. A series of thermomechanical simulations and a forced convection testbed were built for computationally and empirically analyzing the performances of the concepts. The results from the mechanical characterization showed a significant difference between the actual and nominal values of both cell dimensions and mechanical properties. Therefore, the effect of the manufacturing process to such values must be considered before inputting for analyzing the deformation responses. From the thermomechanical analyses, it was found that the mechanical loading might negatively influence the thermal performance if there were not enough mechanical supports from the air-cooling structure. The impact was minimal in the tapered-channel battery assembly. This configuration also significantly reduced the temperature difference on the cell compared with other concepts and the reference design.<br></p>

Deep drawing of paperboard with rigid tools and immediate compression has only a small presence in the market for secondary packaging solutions due to a lack of understanding of the physical relations that occur during the forming process. As with other processes that deal with interactions between two solids in contact, the control of the factors that affect friction is important due to friction’s impact on runnability and process reliability. A new friction measurement device was developed to evaluate the factors influencing the friction behavior of paperboard such as under the specific conditions of the deep drawing process, which differ from the standard friction testing methods. The tribocharging of the contacting surfaces, generated during sliding friction, was determined to be a major influence on the dynamic coefficient of friction between paperboard and metal. The same effect could be examined during the deep drawing process. With increased contact temperature due to the heating of the tools, the coefficient of friction decreased significantly, but it remained constant after reaching a certain charging state after several repetitions. Consequently, to avoid ruptures of the wall during the forming process, tools that are in contact with the paperboard should be heated.

Deep drawing of paperboard with rigid tools and immediate compression has only a small presence in the market for secondary packaging solutions due to a lack of understanding of the physical relations that occur during the forming process. As with other processes that deal with interactions between two solids in contact, the control of the factors that affect friction is important due to friction’s impact on runnability and process reliability. A new friction measurement device was developed to evaluate the factors influencing the friction behavior of paperboard such as under the specific conditions of the deep drawing process, which differ from the standard friction testing methods. The tribocharging of the contacting surfaces, generated during sliding friction, was determined to be a major influence on the dynamic coefficient of friction between paperboard and metal. The same effect could be examined during the deep drawing process. With increased contact temperature due to the heating of the tools, the coefficient of friction decreased significantly, but it remained constant after reaching a certain charging state after several repetitions. Consequently, to avoid ruptures of the wall during the forming process, tools that are in contact with the paperboard should be heated.

To evaluate the influence of different normal forces and contact temperatures on the frictional behavior of paperboard during the deep drawing process, a new measurement punch was developed to measure the normal force, which induced the friction within the gap between the forming cavity and punch. The resulting dynamic coefficient of friction was calculated and reproduced via a new developed substitute test for the friction measurement device, which was first introduced in Lenske et al. (2017). The normal force within the forming gap during the deep drawing process was influenced by the blankholder force profile, the contact temperature, and the fiber direction. The friction measurements with the substitute test showed a strong dependency between the applied normal force and the dynamic coefficient of friction. Furthermore the frictional behavior was influenced by the contact temperature and the wrinkle formation.