International audienceCommercially pure copper was joined to a 1050 aluminum alloy by friction stir welding. A specific configuration where the tool pin was fully located in the aluminum plate was chosen. In such a situation, there is no mechanical mixing between the two materials, but frictional heating gives rise to a significant thermally activated interdiffusion at the copper/aluminum interface. This gives rise to the formation of defect-free joints where the bonding is achieved by a very thin intermetallic layer at the Cu/Al interface. Nanoscaled grains within this bonding layer were characterized using transmission electron microscopy (TEM). Two phases were identified, namely, Al2Cu and Al4Cu9 phases. The nucleation and growth of these two phases are discussed and compared to the standard reactive interdiffusion reactions between Cu and Al

Surface striations with spacing equal to feed rate per rotation and banded structures in the weld nugget are some of the striking features of friction stir welding. However, their formation is still subject to some debate. This study contributes to comprehend their formation by evaluating the possible role played by the eccentricity of the tool during the welding of an aluminium alloy and using a plasticine as its analogue. The eccentric movement is visualized to generate both surface and bulk striations in plasticine. By voluntarily using non optimized welding conditions on aluminium, the material flow has been deduced and confronted with direct visual observations through high speed camera on plasticine. In the non closed section of the weld, two lobes each with thickness equal to feed rate per rotation were observed. First lobe corresponds to flow induced by the pin and tests on plasticine showed constant volume displacement per rotation for a given tool eccentricity. The second lobe is generated by material flow from under the shoulder back to the rear of the pin. The assembling or not of these two lobs behind the pin can explain some of the characteristic patterns observed in the weld nugget such as onion rings, oxide dispersions and cavities.

International audienceWith the aim of providing better control of shooting experiments performed with replicas of prehistoric projectiles, we have conducted an instrumental archaeology study on the efficiency of prehistoric projectile points by placing emphasis on their adhesion and ballistic characteristics. In order to avoid any reproducibility problems, hafting adhesives were made with controlled mixtures of commercial rosin (also called ‘colophany’) and beeswax added as a plasticizer. An original experimental device has been developed to instrument a bow, allowing the control of both the trajectories and the velocities of the different shoots. In the course of an experimental programme on Sauveterrian microliths from the Mesolithic period of the South of France, the experimental system was applied to composite replica projectile tips of Mesolithic hunters. Arrows being shot at transparent targets were filmed in order to evaluate the penetration length and residual damage. Interestingly, this study reveals that the properties of the mixture are highly dependent on the velocity of the arrows. It was shown that—contrary to previous experiments that usually used a mixture in which rosin predominates— the most efficient adhesive is made of 70 wt% beeswax with only 30 wt% rosin. This result is of great importance for improving further shooting experiments and overcoming the problems frequently mentioned due to the loss of the flint armatures before they reach the animal target, or at least before penetration. When using this appropriate mixture, the lateral armatures are resistant to most of the shots. Experiments performed on real boars’ flesh have also shown that the presence of lateral microliths allows the laceration inflicted on the target to be enlarged. Finally, a critical parameter has been identified, which is the location on the arrow of the microlithic element

International audienceBlends of rosin and beeswax were studied in terms of their thermal and mechanical behaviors. Their glass transition and α relaxation were both characterized, either by differential scanning calorimetry or by dynamic mechanical thermal analysis. In this study, we focused particularly on the impact of the microstructure on the mechanical properties, as studied by compression, shear, and nanoindentation tests. It is shown that at room temperature, these blends exhibited a viscous behavior in both the elastic and plastic regimes. From these measurements, a superplastic behavior was highlighted for blends with more than 60 wt % rosin. This superplastic behavior constitutes a real new potential in the mechanical reliability of adhesives based on rosin, which are more generally known for their very brittle behavior. As a result, it should open the way for the design of new shapes

This paper reports on a new method based on the friction stir welding process to join dissimilar metals in butt joint configuration. Two different systems were considered: AA1050 H16 aluminium/ ASTM A284 steel and AA1050 H16/UNS C12200 H01 copper. The unthreaded steel tool pin was positioned in the aluminium plate so that it was tangential to the opposing metal. Bonding was accompanied by interfacial chemical reactions with no significant mechanical mixing. This new solid state welding process is called friction stir diffusion bonding. Room temperature cross-weld tensile strengths up to 82 MPa were obtained for both metal combinations. Microstructure characterisation suggested that higher joint strengths were associated with thinner, ,1 mm thick intermetallic reaction layers at joint interfaces.

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Peut-on espérer faire l’économie de la gestion des muscles et des fonctions dans les plans de traitement orthodontiques ou ortho-chirurgicaux ? En quoi le masseur-kinésithérapeute spécialisé peut-il aider, faciliter, stabiliser le travail de l’orthodontiste et du chirurgien maxillo-facial et éviter les récidives ? L’alignement dentaire et l’équilibre occlusal recherchés par les traitements sont en lien direct avec l’équilibre musculaire de la langue, des muscles peauciers, des muscles masticateurs, des muscles posturaux et les fonctions de la sphère oro-faciale. La réinstallation d’un équilibre entre muscles agonistes et antagonistes passe par un relâchement des muscles contracturés et par une tonification progressive des muscles déficients. La rééducation des dysfonctions oro-maxillo-faciales (linguales, labiales, jugales, masticatoires, ventilatoires) et de la posture globale, ainsi que la gestion des para-fonctions, nécessitent obligatoirement la participation active du patient pour un traitement efficace et pérenne. Cette rééducation est indispensable à l’orthopédie dento-faciale des enfants comme des adultes. L’illustration au travers de cas pratiques montrera ce que la rééducation myo-fonctionnelle peut apporter. Les résultats sont extrêmement satisfaisants pour rétablir les fonctions naturelles sous la condition d’exercices musculaires quotidiens et l’entraînement, tout au long de la journée, des bonnes postures et praxies enseignées, et cela pendant un à plusieurs trimestres sous la supervision du rééducateur.