Reinforced Poly Ether Ether Ketone with 30% of Carbon Fiber (PEEK CF30) offer several thermo-mechanical advantages over standard materials and alloys which make them better candidates in different applications. However, the hard and abrasive nature of the reinforcement fiber is responsible for rapid tool wear and high machining costs. It is very important to find highly effective ways to machine that material. Accordingly, it is important to predict forces when machining fiber matrix composites because this will help to choose perfect tools for machining and ultimately save both money and time. In this study, Artificial Neural Network (ANN) was applied to predict the cutting force components in turning operations of PEEK CF30 using TiN coated cutting tools under dry conditions where the machining parameters are cutting speed ranges, feed rate, and depth of cut. For this study, the experiments have been conducted using full factorial design experiments (DOEs) on CNC turning machine. The results indicated that the well-trained (ANN) model could be able to predict the cutting force components in turning of Carbon Fiber Reinforcement Polymer (CFRP) composites. Complementary results that were not used during derivation of the ANN model have enabled one to assess the validity of the obtained predictions.

New laboratory tests are presented for the experimental evaluation and assessment of the piezoceramic shunted damping (PSD) concept for cantilever Aluminium thin (long) beams bonded symmetrically on their upper/lower surfaces with single pairs of small piezoceramic patches. Following these tests outcome, the PSD efficiency measure is proposed to be the so-called modal effective electromechanical coupling coefficient, which is post-processed from free-vibrations analyses under short-circuit and open-circuit electrodes of the patches. For this purpose, the tests are numerically modelled, analysed, and correlated using ABAQUS® commercial finite element (FE) code. Good tests/models correlations were reached after FE models electromechanical updating. This is attributed to the refined FE models in the sense that they have considered realistic and desirable features such as, electrodes equipotentiality, piezoceramic patches poling orientations (same/opposite), and the corresponding (parallel/series) electric wiring (connections).

In the case of dense and homogeneous canopies, it is well-known that canopy flows are similar to mixing layer flows (so-called mixing layer analogy). When the canopy becomes sparser, a transition between the mixing layer and the boundary layer perturbed by interactions between element wakes occurs. This transition has still to be fully understood and characterized. An experimental work has been developed in order to study this transition for various density canopies.

On s’intéresse au problème de l’optimisation multidisciplinaire, lorsque les disciplinessont prises en compte par des critères qui sont des fonctionnelles de solutionsdistribuées d’équations aux dérivées partielles. Pour le cas de deux disciplines, onpropose une stratégie dans laquelle l’optimisation est décomposée en deux phases : (a) unephase d’optimisation coopérative au cours de laquelle les critères sont améliorés à chaqueitération, et (b) une phase d’optimisation concurrentielle réalisée par un jeu de Nashassocié à un partage adapté des variables.

The problem of the squeezing of a fluid film with a complex rheology is studied. Thefluid is represented by the Phan-Tien and Tanner (PTT) constitutive equation. The goal ofthe paper is to develop an analytical approach which allows one to describe and quantifythis process, which is often present in classical lubrication problems, but particularlyin human joints. The present approach can potentially supplement time-consuming and costlypurely numerical methods which are also susceptible to misleading artifacts. A parametricstudy reveals the effect of fluid elasticity compared to viscous effects and someexplanation is suggested as to their possible links with joint diseases.

Dans cet article, nous présentons une méthodologie numérique pour l'analyse des vibrations non-linéaires des plaques sandwich constituées d'une couche viscoélastique intercalée entre deux parements élastiques. Les modèles de von Karman pour les couches élastiques et de Mindlin pour la couche viscoélastique ont été adoptés. Cette méthode est basée sur une discrétisation par éléments finis et la technique de la balance harmonique couplée à la méthode de Galerkin à un mode. Ainsi, les vibrations non-linéaires des plaques sandwich viscoélastiques ont été modélisées par une simple équation d'amplitude complexe, qui est obtenue par le calcul numérique de deux coefficients complexes. Le premier coefficient permet d'estimer l'amortissement et la fréquence dans le cas linéaire, tandis que le second rend compte des effets non-linéaires en grands déplacements. Les formulations de la pulsation et du facteur de perte en fonction de l'amplitude ont été données analytiquement.Pour valider ce modèle, le calcul numérique d'amortissement dans les cas linéaire et non-linéaire et les courbes de réponses pour différentes structures sandwich viscoélastiques (poutres, plaques) ont été présentés et favorablement comparés à des résultats de la littérature et de l'expérience.

This paper aims at the formulation of a computational model for the simulation of adhesion phenomena in micro-electro-mechanical systems (MEMS) under various environmental conditions. The present approach is based on finite-element (FE) simulations of a representative part of the surface. The micro-scale analyses include the contact behaviour of the asperities and different “proximity interactions” like Van der Waals and capillary forces. The model is first validated in the simple case of a sphere over a flat surface and then applied to a realistic surface sample.

We present a promising approach to reduce the difficulties associated with meshingcomplex curved domain boundaries for higher-order finite elements. In this work,higher-order XFEM analyses for strong discontinuity in the case of linear elasticityproblems are presented. Curved implicit boundaries are approximated inside an unstructuredcoarse mesh by using parametric information extracted from the parametric representation(the most common in Computer Aided Design CAD). This approximation provides local gradedsub-mesh (GSM) inside boundary elements (i.e. an element split by the curved boundary)which will be used for integration purpose. Sample geometries and numerical experimentsillustrate the accuracy and robustness of the proposed approach.

Ce travail est consacré à la présentation d'une nouvelle méthodologie de prévision de l'usinage par enlèvement de copeau. Cette méthodologie est basée sur le couplage fort entre le comportement thermo-mécanique et l'endommagement ductile. Elle utilise également une adaptation de la taille des éléments en fonction de critères physiques (endommagement, plasticité, ...) et géométriques (courbures locales, ...). Cette approche est étudiée et comparée à l'approche classique basée sur le simple écoulement visco-plastique.

Dans ce travail, nous étudions la stabilité linéaire d'une couche poreuse en rotation saturée par un ferrofluide. Le système est placé dans le champ de pesanteur et chauffé par le bas ou par le haut. L'effet de la rotation est limité à la force de Coriolis et le milieu poreux est décrit par le modèle de Brinkman. Le problème aux valeurs propres linéaire est résolu par une méthode de Galerkin modifiée. Le comportement de la différence de température critique est discuté en fonction des différents paramètres du système pour la convection oscillante et la convection stationnaire.

It was recently shown that blind source separation (BSS), as originally developed in the signal processing community, can be used in operational modal analysis to separate the responses of a structure into its individual modal contributions. This, in turn, allows the application of simple single-of-degree-freedom techniques to identify the modal parameters of interest. Several publications have recently attempted to give a posteriori physical interpretations to BSS – as initially developed in telecommunication signal processing – when applied to the field of structural dynamics. This paper proposes to follow the route the other way round. It shows that several separation criteria purposely dedicated to operational modal analysis can be deduced from general physical considerations. Three such examples are introduced, based on very different properties that uniquely characterise a structural mode. The first criterion, coined the “principle of shortest envelope”, conjectures that the envelope of a modal response has, among all possible envelopes, the shortest length. That such a principle leads to the governing differential equation of a single-degree-of-freedom oscillator is proved from calculus of variation. The second criterion, coined the “principle of minimum spectral variance”, conjectures that the frequency spectrum of a structural mode is maximally concentrated around its central frequency. Finally, the third criterion, coined the “principle of least spectral complexity”, states that a structural mode has the lowest possible entropy in the frequency domain. All three criteria can be expressed in terms of a mixing matrix whose columns contain the unknown mode shapes. The recovery of the latter is then trivially achieved by minimising the criteria. Extensive simulations show that the proposed criteria lead to figures of merit very similar to those of the state-of-the-art, while at the same time providing physical insight that other algorithms issued form the signal processing community may dramatically lack.

In the automotive industry, non-asbestos based components, such as brake pads, have beenin high demand due to environmental and human health concerns. Therefore, the purpose ofthis study is to select an alternative friction material, which is eco-aware lightweight,cost effective, and non-toxic. This will be accomplished using Cambridge EngineeringSelector (CES) Edupack software, embedded within an Eco-Audit Tool. For verification, acomparative study using the Pugh method was also investigated. The results show thatKenaf, which is a commodity plant in Malaysia, is the most suitable alternative frictionmaterial that passes all of the design stages and consumes less energy, compared toasbestos and other potential materials.

An emerging research topic in civil engineering is the dynamic interaction between crowdsand structures. Structures such as footbridges, which oscillate due to the crossing of agroup of pedestrians, or stands within stadia or concert halls, which vibrate due to therythmic movement of the audience are of particular interest. The objective of this studyis twofold: modelling the movement of pedestrians with consideration ofpedestrian-pedestrian, and pedestrian-obstacle interactions, and the incorporation of apedestrian-structure coupling in the previous model. Frémond’s model, which allows us tosimulate the movement of an assembly of particles and accounts for collisions amongconsidered rigid particles, is presented and adapted to the crowd by giving a willingnessto the circular particles, which allows each pedestrian to move according to a giventarget. To handle the crowd-structure interaction in the case of lateral oscillations offootbridges, the Kuramoto differential equation governing the time evolution of thelateral motion of each pedestrian is implemented in the previous model. Preliminaryresults obtained from numerical simulations are presented and discussed.

So as to create innovative car silhouettes, we propose in this paper a model based on an Interactive Genetic Algorithm using an encoding of a design solution by a Fourier analysis approach. This model permits the designer to browse through generations of car profiles from an initial population of existing silhouettes. By qualitatively assessing each individual, the designer converges towards solutions complying with his/her requirements and preferences, possibly creating novelty and generating surprise. We describe here tests for assessing the efficiency of this innovative design platform. These tests are mainly based on a similarity index, a similarity measure being the perceived distance between two cars silhouettes. The results highlight a good convergence toward a satisfactory solution. In addition, this design process turns out to be very flexible because of the local and intuitive modifications allowed on a given individual solution at any moment of the design process.

On développe dans ces travaux un outil numérique permettant de simuler le procédé «Friction Stir Spot Welding». Le modèle est basé sur un couplage fluide/solide permettant de décrire l’état de la matière dans toute la structure. Ce modèle s’appuie sur l’élément-fini P1+/P1, développé dans le cas d’un couplage thermomécanique fort, à la fois en mécanique des fluides et en mécanique des solides. Le couplage est associé avec une approche euléro-lagrangienne et intégré au sein d’une nouvelle option du code SYSWELD®. On présente ici une première simulation du procédé Friction Stir Spot Welding.

This project represents a straight continuation of the research activities of the LTI andwhich helped to simulate and understand the electrical response of multi-contact systems.In order to make further progress in the electrical modeling, the electrical transfermodel is applied to the case of bearing operation. The 2D modeling by discrete elementsreproduces the dynamic bearing. The method proposes to take measurements of electricalresistance on bearings to detect defects. This is an original method that stems from workpublished in MSSP. Indeed, while many studies have been conducted on monitoring bearingdefects by analyzing vibration signals, the use of localized electrical measurements onbearings is a promising approach, not yet exploited. The introduction of the firstdefects, as a local breaking of mechanical contact causes periodic disturbances in thecalculation of the electrical resistance. One of our objectives is to characterize thedefects position and the size of the defects, by analyzing disturbances in the electricalmeasurement.

REVIMA is a virtual reality system for maintainability simulation in Aeronautics. It comprises both hardware and software developments, plus system integration. REVIMA required the design of a new haptic system. It is used both to track hand movements and to return force feedback that provides the sensation of working with a physical mock-up. The main software modules are: image generation, collision detection and control. System integration is based on two LAN connected PCs that share the different tasks and data.The visualization module has been built using low-cost graphic systems, and we have thoroughly analysed this problem to achieve a drawing frame rate acceptable for simulation analysis. The models comprise more than two thousand different elements that require about two million polygons to describe their shapes. Different organization strategies have been tested in order to achieve the real simulation goal. We also present the different visualization algorithms we have used.

Fiber metal laminates (FMLs) are high-performance hybrid structures based on alternatingstacked arrangements of fiber-reinforced plastic (FRP) plies and metal alloy layers. Inthis paper, effect of some geometrical and material parameters on free vibrations of FMLplates was studied. The first-order shear deformation theory (FSDT) as well as the Fourierseries method was used to analytically solve the governing equations of the compositeplate. The accuracy of the used method was verified by comparing the Rayleigh-Ritzanalytical method and the ABAQUS finite element software (numerical) method. The resultsindicated that some of the important parameters like sequence of metal layers, aspectratio (a/b) of plate and orientation of compositefibers were important factors affecting free vibration of the FMLs.

This paper presents the mechanical properties of carbon nanocone-based polymer composites in the presence of interphase layer. Some representative volume elements are considered to study the elastic behaviors of the transversely isotropic nanocomposite and the effects of the interphase layer on four of five independent constants related to this model. The finite element method is applied to obtain the results for different elastic moduli and thicknesses of the matrix.

The modelling of the dynamic behaviour of three-dimensional model of two-stage gear system is formulated for general helical gears location. The excitation is induced by the periodic variation of the mesh stiffnesses. This case describes the real working of the gearings. First, the modal analysis of the system is treated. Then, the calculation of the dynamic response is performed by a step-by-step time integration method (Newmark method). Finally, two types of manufacturing defects on the gears are introduced in the model: eccentricity and profile defect. An analysis of the effects of these defects on the gear system dynamic behaviour is then treated.