Influence of Process Parameters on the Deformation of Copper Foils in Flexible-Pad Laser Shock Forming

This paper investigates a new microforming technique, Flexible-Pad Laser Shock Forming (FPLSF), to produce mi-crofeatures on metallic foils without rigid punches and dies. FPLSF uses the laser-induced shock pressure and a flexi-ble-pad to plastically deform metal foils into hemispherical microcraters. In order to understand the deformation characteristics of metal foils in FPLSF, it is necessary to analyze the influence of process parameters on the foil deformation. In this paper, the effects of parameters such as the flexible-pad thickness, confinement layer medium, confinement layer thickness and the number of laser pulses on the depth, diameter and shape of the craters formed on copper foils were investigated. It is found that the flexible-pad thickness should be greater than its threshold value to maximize the deformation of foils. By comparing two different confinement media, namely water and glass, it is observed that hemispherical craters were formed on the copper foils at different laser fluence values tested when using water as the confinement; whereas shockwave ripples were formed on the copper foil at higher laser fluence while using the glass confinement. Using water as confinement medium, an increase in confinement thickness from 4 mm to 7 mm resulted in 48% increase of the crater depth at 7.3 J/cm2. However, at 13.6 J/cm2, reduction in crater depth was observed for thickness greater than 6 mm after an initial increasing trend. Regarding the number of pulses, it is found that increasing the number of pulses from 1 to 3 resulted only in a small increase (less than 1%) in crater depth at 7.3 J/cm2 and 13.6 J/cm2 laser fluence whereas 19.3% increase in depth was observed at larger laser fluence (20.9 J/cm2). It is also observed that the optimum number of pulses to achieve maximum deformation is varying with the laser fluence

Intercompréhension et analogies entre langues voisines : entre transparences et opacités. Le cas des séquences figées

Notre contribution a pour objectif d'examiner les mécanismes cognitifs en jeu dans le cadre de la compréhension en langues voisines et de montrer l'efficience de l'approche par analogie, en prenant pour support de démonstration la question des séquences figées. Après avoir rappelé l'inefficacité de l'approche analytique (médiatisée ou non médiatisée) en compréhension des langues voisines, nous étudierons les diverses relations analogiques qui existent entre les séquences figées équivalentes entre langues voisines et montrerons comment la pratique de l'intercompréhension par approche analogique permet d'accéder, avec plus d'efficience et de subtilité que toute autre approche, à la signification des séquences figées en langues étrangères. Chemin faisant, se renforceront (1) le sentiment que les séquences figées entre langues voisines sont massivement plus transparentes qu'elles ne le paraissent au premier abord, (2) la confirmation que l'approche systémique par analogie constitue l'approche la plus efficiente pour une éducation à l'intercompréhension et au plurilinguisme, et (3) plus largement la piste selon laquelle l'approche systémique par analogie se révèlerait être un vecteur essentiel favorisant l'inclusion culturelle et sociale lors de mobilités dans des espaces européens linguistiquement voisins.The aims of our contribution is to examine the cognitive mechanisms at stake in the frame of the comprehension of neighboring languages and to show the efficiency of the approach by analogy, by means of the example set by phraseological collocations. After recalling the inefficiency of an analytic approach in the understanding (mediatized or non mediatized) between neighboring languages, we will study the various relationships of analogy between equivalent phraseological collocations among neighboring languages. Besides, we will show how the practice of mutual comprehension through an analogical approach provides access, more efficiently and subtly than any other approach, to the meaning of fixed phrases in foreign languages. This sets the stage to strengthen (1) the feeling that the phraseological collocations between neighboring languages are massively more transparent than they appear at first, (2) the confirmation that the systemic approach by analogy is the most efficient approach for an education to intercomprehension and multilingualism, and (3) beyond this, the avenue according to which the systemic approach by analogy could be an essential vector helping cultural and social inclusion during mobility in European territories where are spoken neighboring languages

Developments in finite element simulations of continuous casting

peer reviewedTwo complementary approaches of steel continuous casting modelling using the finite element code LAGAMINE have been developed in the M&S Department. We propose here a description of the context in which the study started, then a description of both macroscopic and mesoscopic approaches. The first one describes the whole continuous casting process, from the free surface in the mould and through the entire machine, including thermal and mechanical behaviour of the steel. The second approach focuses on the prediction of cracks and is developed at the grain scale. Some results are also presented for both models

ETUDE DES INTERACTIONS ENTRE LES CYCLODEXTRINES ET LES MEMBRANES LIPOSOMALES OU BIOLOGIQUES

Résumé : A ce jour, l’utilité des cyclodextrines comme adjuvant pharmaceutique n’est plus à démontrer. En biologie cellulaire, la méthyl-b-cyclodextrine est un outil couramment utilisé par les expérimentateurs. La déstructuration qu’elle induit au niveau des microdomaines membranaires que sont les radeaux lipidiques ou les cavéoles est mise à profit pour l’étude des fonctions cellulaires qui y sont associées.Le but de notre recherche est d’étudier les interactions de différentes cyclodextrines couramment utilisées dans le domaine pharmaceutique avec les constituants des membranes liposomales ou biologiques afin de mieux comprendre les conséquences de ces interactions au niveau cellulaire.L’hypothèse d’une interaction des cyclodextrines avec les constituants lipophiles des membranes cellulaires a souvent été énoncée pour expliquer la cytotoxicité de certains dérivés.Nous avons pu montrer à l’aide de liposomes unilamellaires utilisés comme modèles membranaires, que l’interaction des cyclodextrines avec leurs constituants, en particulier le cholestérol, est en relation avec une perte de l’intégrité de la membrane. Ces premières études nous ont permis de prédire quels seraient les dérivés qui induiraient la cytotoxicité la plus importante.La cytotoxicité importante de certains dérivés méthylés (D.S. proche de 2) a été corrélée avec une capacité d’extraction du cholestérol cellulaire relativement élevée. A l’inverse, nous avons montré que les dérivés faiblement substitués extraient peu le cholestérol, ce qui permet d’expliquer la meilleure tolérance observée au niveau biologique avec la Crysmeb et l’HP-b-CD.Nous nous sommes ensuite intéressés à l’effet de la b-CD et de ses dérivés méthylés sur la déstructuration des microdomaines membranaires. Nous avons étudié la relation entre leur capacité de déstructuration des cavéoles et d’extraction du cholestérol cellulaire. Une extraction relativement élevée du lipide induit un effet important au niveau des microdomaines voire très important dans le cas de la Dimeb, le dérivé ayant l’effet le plus délétère sur l’intégrité des membranes artificielles et biologiques. Un effet moins marqué a également pu être corrélé avec une extraction plus faible du cholestérol par certains dérivés (Crysmeb, Trimeb).Les taux d’extraction du cholestérol cellulaire mesurés sont en bonne corrélation, mis à part pour la Trimeb et la b-CD, avec les résultats des diagrammes de solubilité. La capacité de solubilisation du cholestérol par les cyclodextrines est en accord avec les interactions plus ou moins importantes observées en RMN. Les résultats de mesure de l’intégrité des membranes artificielles correspondent à ceux obtenus avec les membranes biologiques excepté pour la b-CD, cette dernière n’ayant pu être testée dans les mêmes conditions que les autres cyclodextrines sur les liposomes.Il est maintenant admis que les cyclodextrines pourraient avoir un intérêt thérapeutique potentiel. En effet, la modulation des taux de cholestérol par l’utilisation de cyclodextrines pourrait être mise à profit pour traiter des maladies ou infections impliquant ces microdomaines membranaires. Summary :Nowadays, the usefulness of cyclodextrins as pharmaceutical adjuvants is obvious. In cell biology, methyl-b-CD is a tool commonly used by scientists. The disruption of membrane microdomains (such as lipid rafts and caveolae) caused by cyclodextrins is used to study cellular functions.The aim of this research is to study the interactions of various cyclodextrins currently used in pharmaceutical development with the components of liposomal and biological membranes for a better understanding of the consequences of these interactions at the cell level.The hypothesis of an interaction between cyclodextrins and lipophilic components of cell membranes has often been suggested to explain the cytotoxicity of some cyclodextrin derivatives.Using unilamellar liposomes as model membranes, this research has shown that the interaction between cyclodextrins and their components, especially cholesterol, is linked with a loss of membrane integrity. This preliminary study has allowed predicting which derivatives will be the most cytotoxic.The high cytotoxicity of some methylated derivatives (D.S. close to 2) has been correlated with a relatively strong extraction capacity of cell cholesterol. On the other hand, it has been shown that low substituted derivatives do not extract much cholesterol, which is in agreement with the better biological compatibility observed with Crysmeb and HP-b-CD.The research has then focused on the effect of b-CD and its methylated derivatives on membrane microdomains disruption. The relation between caveolae disruption and cell cholesterol extraction capacities has been studied. A relatively strong extraction of the lipid highly disturbs the microdomains and this effect is even more important for Dimeb, the derivative showing the highest loss of integrity of artificial and biological membranes. A less marked effect has also been correlated with the lowest cholesterol extraction capacities of some derivatives (Crysmeb, Trimeb).The measured cell cholesterol extraction rates are in good correlation, except for Trimeb and b-CD, with the results of the solubility diagrams. The cholesterol solubilisation capacity of cyclodextrins is in accordance with the intensity of the interactions observed by NMR. The effects on the integrity of artificial membranes correspond to those obtained with biological membranes except for b-CD, which was not tested on liposomes in the same conditions as those used for the other cyclodextrins. It is now agreed that cyclodextrins could have a therapeutical potential. Indeed, the modulation of cholesterol levels could be applied for treating raft-related infections and diseases

Multi-objective constrained optimization of engine maps

International audienceNowadays, automotive manufacturers are submitted to strong constraints in engine calibration: lowest fuel consumption, emission-control legislation and driver requests for driving comfort and performances. These constraints lead to an increasingly complexity of the engines and thus an increasingly number of parameters to be tuned, making the empirical engine calibration by a scan of parameter values impossible at engine test-bench. New methodologies in automated engine calibration based on statistics and optimization have emerged in order to limit the number of experimental tests to be run. The optimization problem of engine calibration consists in the determination of engine tuning parameter maps that minimize the cumulated fuel consumption and pollutant emissions, under combustion noise constraints, on a driving cycle. The usual way to get this result is to select specific operating points representing this cycle in the engine working range and to define upper bounds applied on the different engine responses (allocations) for each of them, in order to obtain a weighted sum of these local responses respecting the global targets. The underlying problem is a multi-objective optimization problem: different compromises between fuel consumption, noise and pollutant emissions on each operating point are possible. We propose an adapted optimization method based on the MO-CMA-ES method (Multi-objective Covariance Adaptation Evolution Strategy) which takes into account the non trivial limits of the engine parameter variation domains and some robustness constraints. An other point addressed in this paper is the map optimization which consists in a global optimization of engine responses cumulated on the driving cycle. This method avoids the cumbersome choice of allocations for each considered operating point and includes directly the map regularity constraints in map parameterizations. Finally, application on real dataset obtained at automated test-bench for a diesel engine are presented

Developments in finite element simulations of continuous casting

peer reviewedTwo complementary approaches of steel continuous casting modelling using the finite element code LAGAMINE have been developed in the M&S Department. We propose here a description of the context in which the study started, then a description of both macroscopic and mesoscopic approaches. The first one describes the whole continuous casting process, from the free surface in the mould and through the entire machine, including thermal and mechanical behaviour of the steel. The second approach focuses on the prediction of cracks and is developed at the grain scale. Some results are also presented for both models

Analyse mésoscopique par éléments finis de l’endommagement à haute température des aciers microalliés de coulée continue

This thesis addresses the problem of damage at elevated temperature with a view to analysing transverse cracking during the continuous casting of microalloyed steels. Based on the results of a previous project undertaken at the University of Liège to simulate the continuous casting process at the macroscopic level, the present research aims at studying the damage growth using a finite element mesoscopic approach that models the grains structure of the material. The developments are done at the mesoscopic scale using information from both the microscopic and macroscopic levels. In order to determine the constitutive laws governing the damage process at the mesoscopic scale, the physical mechanisms leading to the apparition of cracks during steel continuous casting are first investigated. It is acknowledged that in the studied temperature range (800 to 1200 °C), the austenitic grain boundary is a favourable place for cracks to initiate and propagate. The mechanisms of voids nucleation, growth and coalescence are established, the cavities evolving under diffusion and creep deformations.Having identified the damage mechanisms occurring under continuous casting conditions, a numerical approach for the modelling of these phenomena at the grain scale is proposed. The mesoscopic model, which is implemented in the Lagrangian finite element code LAGAMINE developed at the University of Liège, is built on the basis of a 2D mesoscopic cell representative of the material. The finite element discretization comprises solid elements inside the grains and interface elements on the grains boundaries. An elastic-viscous-plastic law of Norton-Hoff type, which represents the thermo-mechanical behaviour of the material, is associated to the solid elements for the modelling of the grains; and a damage law accounting for cavitation and sliding is linked to the interface elements for the modelling of the damage growth at the grains boundaries. The transfer between the macroscopic and mesoscopic scales is realised by imposing the stress, strain and temperature fields, collected during the parent macroscopic simulation, as boundary conditions on the mesosopic cell.Macroscopic experiments, analytical computations and finite element simulations, as well as literature review and microscopic analyses, are used to define the parameters of the material laws. The experimental results and the identification methodology leading to the definition of the set of parameters specific to the studied steel are described.Finally, the influence of oscillation marks and process defects on cracks formation during the industrial process of continuous casting is analysed. The results are compared with in-situ observations and cracking risk indicators computed by the macroscopic model

Incidencia en las propiedades mecánicas de muros de adobe a escala por la inclusión de tereftalato de polietileno (PET) en su composición

Se realizó la siguiente investigación con dos propósitos: mejorar la técnica de fabricación de adobe y hacer uso del reciclaje, para lo cual se fabricaron 300 adobes a escala 1:400, de los cuales 225 tenían como adición determinado porcentaje de Tereftalato de polietileno (PET). Para saber cuál es la incidencia del tereftalato de polietileno (PET) en las propiedades mecánicas de los adobes, se fabricaron 05 bloques de adobe, 05 pilas de adobe y 05 muros de adobe, sin adición alguna del tereftalato de polietileno, los cuales se sometieron a ensayos a compresión, siendo estos un resultado patrón; para continuar los ensayos se fabricaron 05 bloques de adobe, 05 pilas de adobe y 05 muros de adobe con adición de tereftalato de polietileno en diferentes porcentajes (2%, 4% y 6%), los cuales fueron sometidos a los mismos ensayos. Los resultados evidencian que existe influencia positiva del Tereftalato de Polietileno (PET) en la resistencia del adobe, presentando la mayor resistencia la presentaron bloques, pilas y muretes de adobe con un 6% de Tereftalato de Polietileno en su composición. Sin embargo, el porcentaje recomendado de PET que se adiciona a los prototipos de adobe es el 4%.The following research was carried out with two purposes: to improve the adobe manufacturing technique and make use of recycling, for which 300 adobes were manufactured at a scale of 1: 400, of which 225 had as a certain percentage percentage of Polyethylene Terephthalate (PET). To determine the incidence of polyethylene terephthalate (PET) in the mechanical properties of adobes, 05 adobe blocks, 05 adobe piles and 05 adobe walls were manufactured, without any addition of polyethylene terephthalate, which were submitted to compression tests, these being a standard result; To continue the tests, 05 adobe blocks, 05 adobe piles and 05 adobe walls were added with the addition of polyethylene terephthalate in different percentages (2%, 4% and 6%), which were subjected to the same tests. The results show that there is a positive influence of Polyethylene Terephthalate (PET) in adobe resistance, presenting the greatest resistance presented by blocks, piles and adobe walls with 6% Polyethylene Terephthalate in its composition. However, the recommended percentage of PET that is added to adobe prototypes is 4%.Tesi