Time-dependent sensitivity and uncertainty analyses of an agro-climatic model for the water status management of vineyard

International audienceThis work describes the global sensitivity analysis (SA) of an agro-climatic model embedded in a decision support system (DSS) for the water status management of vineyard in the Languedoc-Roussillon region, France

Numerical Validation of Multiphysic Imperfect Interfaces Models

We investigate some mathematical and numerical methods based on asymptotic expansions for the modeling of bonding interfaces in the presence of linear coupled multiphysic phenomena. After reviewing new recently proposed imperfect contact conditions (Serpilli et al., 2019), we present some numerical examples designed to show the efficiency of the proposed methodology. The examples are framed within two different multiphysic theories, piezoelectricity and thermo-mechanical coupling. The numerical investigations are based on a finite element approach generalizing to multiphysic problems the procedure developed in Dumont et al. (2018)

A Multi-Scale Model of Soft Imperfect Interface with Nonlocal Damage

International audienceThe aim of this paper is to propose a model of bonded interface including nonlocal damage and unilateral conditions. The model is derived from the problem of a composite structure made by two adherents and a thin adhesive. The adhesive is damaged at microscopic level and is subjected to two regimes, one in traction and one in compression. The model of interface is derived by matched asymptotic expansions. In this paper, two cases corresponding to the two regimes are discussed. Moreover, this model can be considered as a model of contact with adhesion and unilateral constraint. At the end of the paper, a simple numerical example is presented to show the evolution of the model

Well-posedness result for a system of random heat equation coupled with a multiplicative stochastic Barenblatt equation

In this paper, a stochastic nonlinear evolution system under Neumann boundary conditions is investigated. Precisely, we are interested in finding an existence and uniqueness result for a system of random heat equation coupled with a Barenblatt's type equation with a multiplicative stochastic force in the sense of Itô. To do so, we investigate in a first step the case of an additive noise through a semi-implicit in time discretization of the system. This allows us to show the well-posedness of the system in the additive case. In a second step, the derivation of continuous dependence estimates of the solution with respect to the data allows us to show the desired existence and uniqueness result for the multiplicative case

Automatic multigrid mesh refinement strategy for precise localized stress concentration simulation

L'interaction mécanique pastille-gaine est un phénomène se produisant dans les réacteurs à eau pressurisée et pouvant mettre à défaut l'intégrité de la gaine entourant le combustible. Dans cet article, la méthode multigrille Local Defect Correction (LDC) est utilisée afin d'améliorer la précision de la simulation de ce phénomène. A partir d'un maillage initial, cette méthode consiste à ajouter récursivement des sous-grilles locales dans des zones où une solution précise est recherchée. Afin de détecter automatiquement les zones à raffiner, la méthode LDC est couplée avec l'estimateur d'erreur a posteriori de type Zienkiewicz et Zhu. Cet estimateur se base sur le fait que les contraintes obtenues par la méthode des éléments finis sont discontinues entre éléments. Il permet ainsi de détecter les zones de singularité de contraintes. La stratégie proposée permet de raffiner automatiquement le maillage dans les zones de concentration de contraintes et également d'arrêter le raffinement quand la solution est suffisamment précise ou lorsque le raffinement n'apporte plus d'amélioration de la solution. Les résultats numériques obtenus sur des cas tests 2D élastiques avec discontinuité de chargement montrent l'efficacité de cette stratégie mais également les limites de l'estimateur d'erreur a posteriori de type Zienkiewicz et Zhu

GFRP beams by bonding simple panels: a low-cost design strategy

Although traditional materials (steel, concrete, timber and masonry) still dominate the building industry, new materials are constantly being explored by engineers and scientists. For instance, the use of the so-called FRPs (Fibre-Reinforced Polymers) is gradually spreading worldwide. FRPs can be qualified as non-corrosive, high mechanical strength and lightweight materials. They have achieved in the last few years a relevant role as a building material for applications regarding both the strengthening and the realization of full-composite structures. Examples of applications of FRPs are numerous [1],[2]. The first buildings made from FRP profiles were single-storey gable frames used in the electronics industry for Electromagnetic Interference (EMI) test laboratories. A five-storey building, named the Eyecatcher Building was erected for the Swiss Building Fair in 1998. The most cost-effective way of producing FRPs is the automated process of pultrusion. This process optimizes the production of bars and thin/thick-walled profiles with both closed and open cross-sections which are constant over the length. Because the industrial process is optimized for mass pultrusion of a limited number of shapes, it is difficult to produce complex shapes with standard cost targets. A low-cost design strategy inspired by modularity, able to exploit the immediate availability of “ready-to-use” standard components, plays a crucial role for the large-scale viability of FRP structures. The idea discussed in this paper is focused exactly on the possibility of achieving a complex FRP shape by bonding an appropriate number of simple pultruded shapes with a common epoxy glue. For example, a generic I-profile may be obtained by bonding three rectangular panels (the top/bottom flanges and the web panel), rather than via a unique pultrusion application. In addition, web-to-flange junctions may also be strengthened by bonding appropriate angle profiles. In this view, the possibility of considering composite profiles of a generic cross-section from simple rectangular panels would be an interesting constructive simplification. For this reason, the authors have recently initiated a large experimental investigation, still under development, in order to compare the flexural behaviour of pultruded FRP profiles with that of bonded FRP profiles. The results have shown the possibility of achieving a very good performance, in terms of both failure load and flexural stiffness, allowing us to consider the bonding system proposed as highly competitive in the field of construction of pultruded profiles

Delamination influence on elastic properties of laminated composites

International audienceThe present work aims to predict the behavior of effective elastic properties for laminated composites, considering localized damage in the interface between two layers. In practical terms, the damage in the adhesion, which influences the effective elastic properties of a laminate, is evaluated like a delamination between adjacent layers. Thus, the effective properties of laminated composites with different delamination extensions are calculated via finite element method and two-scale asymptotic homogenization method. It is investigated how the properties of the laminated composites are affected by the delamination extension and the thickness of the interface between layers. It is possible to conclude that the effective coefficient values decrease as the damage extension increases due to the fact that the delamination area increases. Besides, for all effective coefficients, except the effective coefficients C * 12 , C * 13 , and C * 23 , in the case without delamination, the coefficients decrease as the adhesive region thickness increases, and almost all coefficients decrease for complete separation of the interface. Numerical and analytical results are compared in order to show the potentialities and limitations of the proposed approaches. Finally, a numerical approach is used to simulate a specific case, where the interface is considered a functionally graded material

Efficacy of milbemycin oxime/afoxolaner chewable tablets (NEXGARD SPECTRA®) against Capillaria aerophila and Capillaria boehmi in naturally infected dogs

BACKGROUND: Capillaria aerophila and Capillaria boehmi parasitize the respiratory system of wild and domestic carnivores. Capillaria aerophila inhabits the trachea and bronchi of dogs and cats, while C. boehmi affects the nasal cavities and sinuses of dogs. In dogs the infection may be subclinical or characterized by varying respiratory distress.METHODS: The present study evaluated the efficacyof an oral formulation containing milbemycin oxime and afoxolaner (NEXGARD SPECTRA) in dogs naturally infected with C. aerophila and/or C. boehmi from three enzootic areas of Italy. Dogs were enrolled pending fecal examination and molecular confirmation of respiratory capillarioses. Dogs were allocated in two groups: Group 1 (G1, 25 dogs), treated with a negative control product with no anthelmintic activity (afoxolaner, NEXGARD), and Group 2 (G2, 26 dogs), treated with NEXGARD SPECTRA. At the day of treatment administration (Day 0), all dogs were clinically examined. Dogs were again subjected to clinical and fecal examinations at Days 28 (±4) and 56 (±2). The primary criterion for treatment efficacy was the reduction of fecal Capillaria egg counts in G2 compared with G1. The regression of/recovery from baseline clinical signs was considered as a further efficacy criterion.RESULTS: Percentage reduction of fecal Capillaria egg counts in the NEXGARD SPECTRA group compared to the control group was >97% on Day 28 and 100% on Day 56, respectively (p<0.05 for both time points). Twelve of the 13 dogs in the NEXGARD SPECTRA group with respiratory signs prior to treatment were free of clinical signs at the end of the study. Conversely, the six control group dogs with respiratory signs prior to treatment remained symptomatic.CONCLUSIONS: Results of the present study showed that NEXGARD SPECTRA was safe and highly efficacious in the reduction of C. aerophila and C. boehmi eggs after one treatment with a complete reduction of the egg output after the second administration associated with a recovery from respiratory signs

Shock characterization for fused silica glass direct bonding with a new experimental bench

 The fused silica glass direct bonding consists in joining two surfaces without using any adhesive. This technology is used in particular to manufacture optical systems like optical slicers or interferometers used in terrestrial optics. The final aim of this investigation consist to spatialize this technology. But the spatial environment is totally different from the terrestrial one. A satellite may undergo shocks, vibrations or thermal fatigue. It is necessary to characterize with accuracy the direct bonded interface under these solicitations to respect the European Space Agency requirements. In this context, a new test machine has been developed to characterize interface shock resistance. The new machine design is based on two principles. The first one, the Arcan assembly modified developed by Cognard, consists in loading an adhesively-bonded assembly with different loading types, tensile mode or shear mode. It is constituted by two half disks with several attachment points on their periphery. These attachment points allow installing the mount on a standard tensile testing machine. The second, the Beevers and Ellis testing machine, imposes a tension load on a specimen by the falling weight along a tube connected to the specimen. In our concept, we replaced the specimen in Beevers and Ellis machine by the Arcan assembly. A test campaign on the fused silica glass direct bonding has been performed with the new experimental device. The specimens are solicited by shocks in pure traction and shear mode. The aim consists in measuring the fracture energy. This energy is calculated in function of the mass and the drop height, and for all tests the drop height is the same to keep a constant speed. In order to complete the dynamic study, a static study is performed with the Arcan device on a standard testing machine in traction, shear and a mixed mode (I+II)

Resolution numerique de problemes de frottement de Coulomb. Acceleration de convergence par une methode multigrilles interne

SIGLEINIST T 73363 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc