Discrete ply model of circular pull-through test of fasteners in laminates

In aeronautical structures, assemblies with thin laminates are becoming increasingly usual, especially for fuselage design. In these structures, out-of-plane loads can appear in bolted joints and can lead to progressive punching of the fastener’s head in the laminate resulting, in some cases, in a failure mode called pull-through [1]. This complex phenomenon, which occurs in assemblies, was studied firstly by using a simplified ‘‘circular’’ pull-through test method. Qualitative micrographic examinations showed damage very similar to that observed in impacted specimens. The research presented here extends the Discrete Ply Model Method (DPM) developed by Bouvet et al. [2] to this case. The finite elements model is based on a particular mesh taking ply orientations into account. Cohesive elements are placed at the interfaces between solid elements to represent matrix cracks and delamination, thus allowing the natural coupling between these two damage modes to be represented. The model shows good correlation with test results, in terms of load/displacement curve, and correct prediction of the damage map until failure, including the splitting phenomenon

Elaboration du premier programme d'éducation thérapeutique du patient en cancérologie à l'hôpital Paul Brousse, IMMPaCT (aboutissement du parcours d'une interne en pharmacie)

PARIS-BIUP (751062107) / SudocSudocFranceF

The withdrawal of the lower limit of the Posidonia oceanica seagrass meadow in the Bay of Hyères (NW Mediterranean) : a combination of natural and human-induced recent and ancient phenomena ?

International audienceThe Posidonia oceanicaseagrass meadows are very sensitive to disturbance of human or natural origin. Here we consider the losses of the seagrass localizednear the lower limit of the meadowinthe Bay of Hyères(France). Samples of dead mattewere taken nearand beyond the current lower limit of the meadow, between 26 and 37 m depth. Radiocarbon 14C analyses were used for dating the withdrawal. The death of P. oceanicapossibly occurred between 160±100 (-29 m) and 1050±110 years BP (-37 m). The deeper and the further from the shore the sampled dead mattewas, the more ancient it was. This withdrawal appears to be a general feature, which concerns both highly human-impacted areas (Bay of Hyères)and pristine areas, such as Port-Cros Island (National Park). Several non-mutually exclusive hypotheses might explain this recent vs. ancient and actual vsapparent withdrawal: (i)trawling;(ii)post mortem erosion of the roof ofthe dead matte, by hydrodynamismor trawling; (iii)compaction of dead matteover time; (iv)current andancient rise in sea level; (v)current and past climate changeand/or (vi)human induced changes (e.g. turbidity).The lower limit withdrawal is more markedin highly human-impacted areas than in pristine areas, whereitmayreflect global forcings such as sea level rise, warmingandclimate episodes

Te-rich Ge-As-Se-Te bulk glasses and films for future infrared integrated optics

International audienc

Application of high-performance computing to a bolt static tensile test

International audienceFaced with an increasingly fast-changing market, airplane manufacturers have to reduce the development time of their new programs whilst dealing with more and more complex composite structures. The European project Maaximus (More Affordable Aircraft Structure Lifecycle through eXtended, Integrated & Mature nUmerical Sizing) aims at providing methods and tools to enable the fast development and right-first-time validation of a highly optimized composite airframe. In this context, accurate models of fasteners are crucial to ensure correct structure modeling at a higher level. The present study focuses on the mechanical behavior of a threaded assembly subjected to an axial tensile load. After a review of the state-of-the-art in this domain, the first part of the paper shows what benefits can be expected from explicit simulation for large quasistatic models. Parallelization strategies for High-Performance Computing (HPC) are presented, bringing out the need for consistency between the parallelization strategy and the computation structure. These simulation techniques are then applied to the modeling of a tensile test of a fastener. The results of corresponding experiments for two fastener diameters are presented. A successful correlation between simulations and experiments is found, both qualitatively and quantitatively. This study shows the efficiency of a well-chosen resolution algorithm in a coherent HPC environment for solving large non-linear models

Leaf bud endodormancy release in peach trees : evaluation of temperature models in temperate and tropical climates

International audienc

Modélisation par éléments cohésifs de l'essai d'arrachement de fixations dans un stratifié

National audienceDans les structures aéronautiques, il est de plus en plus fréquent de voir des assemblages mettant en jeu des stratifiés d'épaisseur faible. Dans certains cas comme les jonctions en L, des efforts hors plan apparaissent au niveau de l'assemblage qui peuvent conduire à un mode de rupture appelé quelque fois déboutonnage mais plus couramment par l'anglicisme " pull-through ". Ce mode de rupture est généré par le poinçonnement progressif du stratifié par la tête de la fixation avec parfois au final le passage complet de la tête au travers du stratifié [1]. Des analyses micrographiques qualitatives ont montré que ces endommagements étaient très similaires à ceux observés en impact. De ce fait, il a été envisagé d'étendre l'approche développée par Bouvet et al. [2] à cette problématique. Le modèle éléments finis est basé sur un maillage particulier qui suit les orientations des plis. Des éléments cohésifs sont disposés aux interfaces des éléments volumiques pour pouvoir représenter la fissuration matricielle ou le délaminage et permettre un couplage naturel entre ces deux endommagements. Le modèle permet une bonne comparaison avec les essais réalisés en terme de graphe effort d'arrachement/déplacement de la tête de vis ainsi qu'une prédiction correcte des cartographies d'endommagement

Identification of the Cauliflower mosaic virus receptor in its insect vector et characterisation of the acrostyle : antibodies library and peptide array approaches

National audienc

Approches du repos d'une espèce tempérée, le pêcher, en région tropicale et perspectives de son contrôle rationnel

National audienc