Hybrid (bolted/bonded) joints applied to aeronautic parts : analytical one-dimensional models of a single-lap joint

The load transfer in hybrid (bolted/bonded) single-lap joint is complex due to the association of two different transfer modes (discrete and continuous) through elements with different stiffness. Analytical methods exist for these two different modes, when considered separately. In this paper two one-dimensional elastic analytical models are presented for the determination of the load transfer in single lap configuration. The first one is developed by using the integration of the local equilibrium equations. From this first method an elastic-plastic approach is presented. The second one uses the Finite Element Method, introducing a new element called “bonded-bar”. These models are robust, easy to use and provide the same results. They allow to analyze the load transfer and to evaluate different geometric and mechanical parameters’ influence. Thus they represent the first step for the design of a hybrid joint able to replace its bolted equivalent used on aircraft

Faisabilité d'assemblages mixtes boulonnés-collés en aéronautique

L'idée de l'assemblage hybride est de réduire le transfert aux fixations sous charge de fatigue, de manière à dépalcer le site critique en zone non trouée tout en garantissant la tenue aux charges extrêmes

Contribution aux assemblages hybrides boulonnés collés aéronautiques : modélisation analytique unidimensionnelle en simple cisaillement

Le calcul du transfert de charge dans les jonctions a été traité par des approches analytiques d’une part dans le cas des jonctions boulonnées et d’autre part dans celui des jonctions collées. Dans cet article, nous étudions le cas d’une jonction hybride boulonnée collée qui associe les deux modes de transfert (discret et continu) dans une configuration en simple cisaillement. Nous présentons une modélisation analytique monodimensionnelle qui prend en compte la rigidité des différents composants. Simple à mettre en oeuvre, elle permet d’analyser le transfert de charge et d’évaluer l’influence des différents paramètres géométriques et mécaniques. Son exploitation est intéressante dans le cadre du pré-dimensionnement d’une jonction hybride apte à remplacer son équivalent boulonné sur avion

Using lasers for cleaning ceramic and plaster patrimonial objects

International audienceTraditional cleaning techniques (sandblasting, chemical, ...) turn out to be ineffective or damaging on some ceramics and plaster objects. It's especially true on outdoor ceramics covered with black crust or indoor biscuits wares and plasters exposed to dust and repeated handling. The use of lasers to remove dirt, such as for stone, has then been considered. This paper study the behavior of these materials under the impact of different type of lasers irradiation (Nd:YAG first and third harmonic, excimer,...). According to the type of dirt and underlying material, the effectiveness of cleaning depends on the laser wavelength and its energy density. The results are satisfactory with no damage and no coloration change on plaster cleaning by Nd:YAG third harmoni

PLM-based approach for collaborative design between OEM and suppliers : case study of aeronautic industry.

To achieve different assembly operations on the aircraft structure, the aeronautic OEM needs to create and manage various fixture tools. To cope with these needs, the OEM begun to adopt the supplier integration into the tooling development process. This paper presents a conceptual PLM-based approach to support new business partnership of different suppliers. The new business partnership aims to improve the role of supplier in the different tasks of design, configuration and fabrication of the tooling. The use of the PLM concepts is proposed to enhance the collaboration between OEM and the equipment's suppliers. UML models are proposed to specify the structure of the PLM solution. These models describe the relation between the aircraft assembly project, and the tooling design process

Changes in urine composition after trauma facilitate bacterial growth.

International audienceUNLABELLED: ABSTRACT: BACKGROUND: Critically ill patients including trauma patients are at high risk of urinary tract infection (UTI). The composition of urine in trauma patients may be modified due to inflammation, systemic stress, rhabdomyolysis, life support treatment and/or urinary catheter insertion. METHODS: Prospective, single-centre, observational study conducted in patients with severe trauma and without a history of UTIs or recent antibiotic treatment. The 24-hour urine samples were collected on the first and the fifth days and the growth of Escherichia coli in urine from patients and healthy volunteers was compared. Biochemical and hormonal modifications in urine that could potentially influence bacterial growth were explored. RESULTS: Growth of E. coli in urine from trauma patients was significantly higher on days 1 and 5 than in urine of healthy volunteers. Several significant modifications of urine composition could explain these findings. On days 1 and 5, trauma patients had an increase in glycosuria, in urine iron concentration, and in the concentrations of several amino acids compared to healthy volunteers. On day 1, the urinary osmotic pressure was significantly lower than for healthy volunteers. CONCLUSION: We showed that urine of trauma patients facilitated growth of E. coli when compared to urine from healthy volunteers. This effect was present in the first 24 hours and until at least the fifth day after trauma. This phenomenon may be involved in the pathophysiology of UTIs in trauma patients. Further studies are required to define the exact causes of such modifications

Pre-Hawking Radiation from a Collapsing Shell

We investigate the effect of induced massive radiation given off during the time of collapse of a massive spherically symmetric domain wall in the context of the functional Schr\"odinger formalism. Here we find that the introduction of mass suppresses the occupation number in the infrared regime of the induced radiation during the collapse. The suppression factor is found to be given by $e^{-\beta m}$, which is in agreement with the expected Planckian distribution of induced radiation. Thus a massive collapsing domain wall will radiate mostly (if not exclusively) massless scalar fields, making it difficult for the domain wall to shed any global quantum numbers and evaporate before the horizon is formed.Comment: 10 pages, 3 figures. We updated the acknowledgments as well as added a statement clarifying that we are following the methods first laid out in Phys. Rev. D 76, 024005 (2007

Approche couplée essais-calculs pour l’analyse du comportement des assemblages boulonnés en composites stratifiés

Approche couplée essais-calculs pour l’analyse du comportement des assemblages boulonnés en composites stratifiés

Electroweak Baryogenesis and Standard Model CP Violation

We analyze the mechanism of electroweak baryogenesis proposed by Farrar and Shaposhnikov in which the phase of the CKM mixing matrix is the only source of $CP$ violation. This mechanism is based on a phase separation of baryons via the scattering of quasiparticles by the wall of an expanding bubble produced at the electroweak phase transition. In agreement with the recent work of Gavela, Hern\'andez, Orloff and P\`ene, we conclude that QCD damping effects reduce the asymmetry produced to a negligible amount. We interpret the damping as quantum decoherence. We compute the asymmetry analytically. Our analysis reflects the observation that only a thin, outer layer of the bubble contributes to the coherent scattering of the quasiparticles. The generality of our arguments rules out any mechanism of electroweak baryogenesis that does not make use of a new source of $CP$ violation.Comment: 36 pages, in LaTeX, one LaTeX figure included, 5 others available upon request, SLAC-PUB-647

Séquenceur mémoire pour applications multimédias temps réel gérant les séquences d'accès indéterministes

Dans le domaine du traitement du signal et de l'image, les applications multimédias sont souvent caractérisées par un grand nombre d'accès aux données. Pour la plupart de ces applications, les accès aux données structurées (tableaux, vecteurs) sont réguliers et périodiques. Dans ces conditions, il est possible et efficace de générer des contrôleurs pipeline d'accès à la mémoire. Cette technique est utilisée afin d'améliorer les accès en mode pipeline autorisés par les mémoires actuelles. On utilise pour cela des composants matériels dédiés pour générer les adresses et pour packer/dépacker les données. Dans cet article nous présentons l'architecture d'un séquenceur mémoire qui permet de prendre en compte de manière efficace les accès prédictibles aussi bien que les séquences d'accès non prédictibles (calculs d'adresses dynamiques) de manière pipeline