Simulating the sound transmission loss of complex curved panels with attached noise control materials using periodic cell wavemodes

International audienceThe sound transmission loss of complex curved aircraft panels under diffuse acoustic field excitation is experimentally and numerically studied. Two different aircraft sidewall panels are considered: a thick composite sandwich panel and a thin aluminium panel with stiffening elements (stringers and frames). Both bare configuration and with attached soundproofing material are tested in laboratory conditions in coupled rooms. The numerical approach relies on a wave finite element method including modal order reduction at cell scale and an extension based on the transfer matrix method, for the inclusion of poroelastic treatments. The results obtained show that the proposed numerical scheme is efficient for predicting the sound transmission loss of such complex structures

Stacking layer sequence effects for glass fibre/epoxy resin cross-ply laminates

This work describes the effect of the stacking sequence over the distribution of the deformation and stress fields through the thickness of the laminate. The laminates are made of epoxy resin and glass fibres, having the ratio of 0 to 90° plies equal to 1. This stacking sequence is applied to obtain composite laminates with different thicknesses. The study presented in this paper is focused on the linear static behaviour of the cross/ply laminates by means of finite-element models developed using the commercial codes ANSYS 6.1 and LUSAS 15.3. The numerical models represent three-point bending loading cases. A viscoelastic analysis of the laminates based on the correspondence principle is also performed. The results from the finite element models show good agreement with those obtained using the Classical Laminate theory, while the viscoelastic storage modulus and loss factors distribution indicate the best stacking sequences for structural dynamics applications, such as spring leaves for novel car suspension systems.Оцінюється вплив послідовності укладання шарів ламіната на розподіл полів деформацій і напружень по його товщині. Ламінатні зразки складаються із шарів епоксидної смоли і скловолокна, при цьому співвідношення шарів з орієнтацією волокон від 0 до 90° дорівнює одиниці. Таке співвідношення шарів використовувалося при виготовленні ламінатів різної товщини. Описано напружено-деформований стан багатошарових ламінатів при лінійному статичному навантаженні за допомогою скінченноелементних моделей стандартних програмних пакетів ANSYS 6.1 та LUSAS 15.3. Числове моделювання виконано для триточкового згину ламіната. Проведено розрахунок матеріалу у в ’язко-пружному стані, що базується на принципі подібності. Результати розрахунків методом скінченних елементів добре узгоджуються з отриманими у рамках класичної теорії ламінатів. Для конкретних значень модулей в ’язко-пружності і розподілу різних параметрів визначено послідовність укладання шарів стосовно динамічних задач для таких конструкцій, як ламінатні ресори для нових автомобільних підвісних систем.Оценивается влияние последовательности укладки слоев ламината на распределение полей деформаций и напряжений по его толщине. Ламинатные образцы состоят из слоев эпоксидной смолы и стекловолокон, причем соотношение слоев с ориентацией волокон от 0 до 90° равно единице. Такое соотношение слоев использовалось при изготовлении ламинатов различной толщины. Описано напряженно-деформированное состояние многослойных ламинатов при линейном статическом нагружении с помощью конечноэлементных моделей стандартных программных пакетов ANSYS 6.1 и LUSAS 15.3. Численное моделирование выполнено для случая трехточечного изгиба ламината. Выполнен расчет материала в вязкоупругом состоянии, основанный на принципе подобия. Результаты расчета методом конечных элементов хорошо согласуются с полученными в рамках классической теории ламинатов. Для конкретных значений модулей вязкоупругости и распределения различных параметров определена оптимальная последовательность укладки слоев применительно к динамическим задачам для таких конструкций, как ламинатные рессоры для новых автомобильных подвесных систем

NUMERICAL MODELING OF A TIMOSHENKO FGM BEAM USING THE FINITE ELEMENT METHOD

In this paper, a finite element procedure for static analysis of functionally graded material (FGM) beam is presented. The material properties of the beam are assumed to vary continuously along the beam thickness by a power-law distribution. The assumed field displacements equations of the beam are represented by Euler-Bernoulli and first order shear deformation theories. A simply supported beam subjected to uniform load for different length-to-thickness ratio has been chosen. The influences of span-to-depth and the volume fraction index on the mid plane deflections, and stresses distribution along the thickness of the beam are examined. The obtained results are compared with the existing solutions to verify the validity of the developed theorie

CONTRIBUTION A L’IMPLEMENTATION DE LOIS DE COMPORTEMENT SOUS PLAXIS. - CAS DES MATERIAUX VISQUEUX –

L’objectif principal de ce travail se veut une contribution à la programmation des lois rhéologiques et de leur implémentation sur des codes de calcul dynamiques tel que PLAXIS par le biais d’une DLL « Dynamic Link Library ». La première tâche est consacrée à la compréhension et à la maîtrise de la technique de programmation dynamique à travers les DLL (moyennant un langage de programmation sous une plate forme Windows). Il a été question d’implémenter des lois simples de types élastique linéaire (isotrope et orthotrope), et ce en situation drainée ou non drainée. Afin de pouvoir prédire le comportement des matériaux visqueux, Il a été procédé à la programmation de la loi viscoplastique de Lemaitre pour le fluage ainsi que l’implémentation de la loi viscoplastique de Koppejan modifiée. Ces lois ont été validées par une série de simulations. Ces dernières ont été soumises, par la suite, à la confrontation d’une part avec les modèles existants et d’autre part avec une solution analytique de référence.    The objective of this work is to provide a contribution to the programming of rheological laws and implement then on dynamic design cods standards such as PLAXIS through a DLL “Dynamic Link Library”. The first task of this work is to understand and master the technique of dynamic programming through DLLs (using a programming language under Windows platform). In order to familiarize with this technique, we started by implementing simple laws such as linear elastic isotropic model and linear elastic orthotropic model, in a drained and undrained situation. In order to predict the behavior of viscous materials, we programmed Lemaitre’s viscoplastic law for creep computation, as well as the implementation the viscoplastic relationship of law of Koppejan modified. These laws were validated by modeling a series of simulation tests which were then compared with existing models or with analytical solution reference

Etude théorique du comportement des tirants d’ancrage dans un sol pulvérulent

Les tirants d‟ancrages sont connus depuis plusieurs dizaines d'années. En particulier, ils sont souvent appliqués avec succès pour la stabilisation des talus rocheux. Depuis les années 60, les tirants d‟ancrage sont utilisés dans les terrains meubles par utilisation de l'injection. Le principe de base consiste à mobiliser un certain volume du terrain, la difficulté principale dans la compréhension d‟un tel mécanisme réside dans le nombre élevé de variable : Résistance du sol, résistance de l‟acier, dimensions des perforations, caractéristique du coulis d‟injection, angle de frottement et dilatance. Ce travail présente les résultats de l‟étude théorique du comportement des tirants d‟ancrage dans un sol pulvérulent qui consiste à déterminer un modèle basé sur l‟approche cinématique de la théorie de l‟analyse limite, dans le cas du critère de Mohr-Coulomb. La comparaison des résultats obtenus avec l‟approche théorique et l „approche empirique laisse conclure que le type de rupture du sol obtenu autour du tirant est proche de la réalité.Mots clés : Tirants D’ancrage Modèle - Approche Cinématique - Analyse Limite -Géotechnique

An experimental and numerical analysis of concrete walls exposed to fire

International audienceTo evaluate the performance of concrete load bearing walls in a structure under horizontal loads after being exposed to real fire, two steps were followed. In the first step, an experimental study was performed on the thermo-mechanical properties of concrete after heating to temperatures of 200-1000°C with the purpose of determining the residual mechanical properties after cooling. The temperature was increased in line with natural fire curve in an electric furnace. The peak temperature was maintained for a period of 1.5 hour, then allowed to cool gradually in air at room temperature. All specimens were made from calcareous aggregate to be used for determining the residual properties: compressive strength, static and dynamic elasticity modulus by means of UPV test, including the mass loss. The concrete residual compressive strength and elastic modulus values were compared with those calculated from Eurocode and other analytical models from other studies, and were found to be satisfactory. In the second step, experimental analysis results were then implemented into structural numerical analysis to predict the post-fire load-bearing capacity response of the walls under vertical and horizontal loads. The parameters considered in this analysis were the effective height, the thickness of the wall, various support conditions, and the residual strength of concrete. The results indicate that fire damage does not significantly affect the lateral capacity and stiffness of reinforced walls for temperature fires up to 400°C

Verification of the fire resistance of reinforced concrete columns

This paper is devoted to nonlinear numerical modeling of reinforced concrete columns subjected to fire. In this work we analyze reinforced concrete columns loaded by eccentric compressive forces and exposed to a standard fire. That the columns have an extremely important role in building, the verification of fire resistance in fire conditions is crucial. The analysis is divided into two steps. In the first step we make the thermal study of column. It follows the temperatures depending of time that we use in the second stage for the mechanical study, where we get the variation of different parameters such as bending moment, stresses, displacements and tangent modulus