The Onera elsA CFD software is both a software package capitalizing theinnovative results of research over time and a multi-purpose tool for applied CFD andmulti-physics. The research input from Onera and other laboratories and the feedback fromaeronautical industry users allow enhancement of its capabilities and continuousimprovement. The paper presents recent accomplishments of varying complexity from researchand industry for a wide range of aerospace applications: aircraft, helicopters,turbomachinery...

Additive manufacturing processes, used for more than 25 years, are no longer confined torapid prototyping applications. Mostly used nowadays in niche markets (medicalapplications, aerospace...) to manufacture metallic parts, they should provideimprovements in terms of time-to-market, ecological impact and design compared totraditional industrial processes. Current metallic additive manufacturing studied in thispaper are Selective Laser Sintering, Direct Metal Laser Sintering, Selective LaserMelting, Electron Beam Melting and Direct Metal Deposition. The performances of theseprocesses are investigated through criteria derived from the time cost quality triangleand some prospects concerning these processes are given.

Most of the norms used in the field of digital image (and volume) correlation to registertwo images (or volumes) lead to ill-posed problems. One of the frequent solutions is toenforce a restricted kinematics requiring a compromise between the richness of thesolution (i.e., the spatial resolution) and the measurement uncertainty. An alternativeroute is to use a displacement norm that permits to alleviate this compromise by the meansof a mechanical regularization used when the gray levels do not give enough information.It is then possible to compute a displacement vector for each pixel orvoxel, inducing lower residuals (in terms of experimental data) whiledecreasing the noise sensitivity. The resolution performance of these different approachesis discussed, and compared for the analysis of a tensile test on a cast iron specimenbased on a pair of tomographic images. As representative reconstructed volumes lead to alarge number of degrees of freedom, a dedicated GPU computational strategy has beendeveloped and implemented.

In this paper, composites based on unsaturated polyester resin reinforced with short Alfa fibers are studied in detail. Alfa fibers have been previously treated with various concentrations NaOH (1, 3, 5, 7%) during 24 h. The influence of alkali treatment on fiber morphology is analyzed. Analysis by FTIR and X-ray diffraction showed physico-chemical changes in Alfa fiber treated surfaces. SEM observations also helped to highlight these changes. The results of static tests on composites showed improvements in tensile and flexural strengths of composites reinforced with the treated fibers, particularly the composite with treated fibers at 7% NaOH. These improvements were about 30% and 50%, respectively, compared to untreated fiber reinforced composite.

Simple process models are applied to predict microstructural changes due to the thermal cycle imposed in friction stir welding. A softening model developed for heat-treatable aluminium alloys of the 6000 series is applied to the aerospace alloy 2014 in the peak-aged (T6) condition. It is found that the model is not readily applicable to alloy 2024 in the naturally aged (T3) temper, but the softening behaviour can still be described semi-empirically. Both analytical and numerical (finite element) thermal models are used to predict the thermal histories in trial welds. These are coupled to the microstructural model to investigate: (a) the hardness profile across the welded plate; (b) alloy softening ahead of the approaching welding tool. By incorporating the softening model applied to 6082-T6 alloy, the hardness profile of friction stir welds in dissimilar alloys is also predicted.

Water-lubricated bearings are expected to be widely used because of convenience, green,safe and energy saving. The purpose of this study is to provide references for designinghydrodynamic water-lubricated step thrust bearings. The numerical analysis is undertakenunder the condition of different pad dimensions, step heights, step positions, water filmthicknesses and rotational speeds of thrust rings based on computational fluid dynamics(CFD). The results including pressure distribution, load carrying capacity, frictiontorque and friction coefficient are gained and compared for optimizing geometryparameters. A reference to determine water-lubricated step thrust bearing dimensions and aformula to check the minimum water film thickness are proposed.

This paper presents the application of new time frequency method, ensemble empirical modedecomposition (EEMD), in purpose to detect localized faults of damage at an early stage.EEMD is a self adaptive analysis method for non-linear and non-stationary signals and itwas recently proposed by Huang and Wu to overcome the drawbacks of the traditionalempirical mode decomposition (EMD). The vibration signal is usually noisy. To detect thefault at an early stage of its development, generally the residual signal is used. Thereexist different methods in literature to calculate the residual signal, in this paper wemention some of them and we propose a new method which is based on EEMD. The results givenby the different methods are compared by using simulated and experimental signals.

Quasi-unidirectional glass fibre non crimp fabric composites are routinely used in windenergy applications. An important factor to consider in this type of application is thefatigue behaviour of the materials. The present paper gives an overview of the currentapproach to material fatigue testing and design in the wind energy industry, as well as areview of available material data for the fatigue of unidirectional glass fibrecomposites. Both “pure” unidirectional and quasi-unidirectional (NCF-based) materials areconsidered.

In this study, the dynamic analysis of Pipeline Inspection Gauge (PIG) flow control innatural gas and liquid pipeline is considered. The basic equations are differential formsof the mass and linear momentum for compressible liquid and gas flows. The fluid flowequations and a linear momentum equation of the PIG are solved simultaneously using anappropriate numerical method. Solution of these nonlinear equations results in a set ofdiagrams for the variations of the fluid pressure, mass flow rate of the gas and the PIGvelocity through the pipeline. Comparing the results of mathematical model for the PIGwith the established experimental data in a segment of Ahwaz gas pipeline shows a goodagreement between the measurements and computations.

A non-intrusive stochastic finite-element method is proposed for uncertainty propagation through mechanical systems with uncertain input described by random variables. A polynomial chaos expansion (PCE) of the random response is used. Each PCE coefficient is cast as a multi-dimensional integral when using a projection scheme. Common simulation schemes, e.g. Monte Carlo Sampling (MCS) or Latin Hypercube Sampling (LHS), may be used to estimate these integrals, at a low convergence rate though. As an alternative, quasi-Monte Carlo (QMC) methods, which make use of quasi-random sequences, are proposed to provide rapidly converging estimates. The Sobol' sequence is more specifically used in this paper. The accuracy of the QMC approach is illustrated by the case study of a truss structure with random member properties (Young's modulus and cross section) and random loading. It is shown that QMC outperforms MCS and LHS techniques for moment, sensitivity and reliability analyses.

This paper deals with analysis of the cutting process, on a macro and micro scale, in the deep hole drilling with BTA system. An experimental procedure is developed to highlight the impact of cutting speed and feed rate on the cutting process when machining the 18MND5 steel. Parameters based on dimensional characteristics of chips are introduced to quantify the morphology of chips generated by central, intermediate and external inserts of the complex BTA drilling tool. From observation of the chips morphology (flat, curved and spiral) and the measurement of the chips width, the provenance of each chip with respect to cutting inserts is identified. Then, the Chip Compression Ratio is evaluated for each cutting condition, indicating the amount of plastic strain in chips. Thanks to the introduction of a new parameter, denoted as Chip Fragmentation Ratio, it is found that the cutting speed has a little influence, compared to the feed rate, on the chips size. Based on this quantitative analysis, the optimal range of cutting conditions for the BTA deep hole drilling is discussed. It is mentioned that although increasing the feed rate promotes the chips fragmentation and increases the material removal rate (increasing productivity), an upper limit is to determine to prevent excessive flank wear. Also, the cutting speed should be limited to avoid excessive crater wear.

Laser polishing is a finishing process based on melting material, with the objective of improving surface topography. Some operating parameters must be taken into consideration, such as laser power, feed rate, offset, and overlap. Moreover, because of its dependence on the primary process, the initial topography has also an impact on the final result. This study describes a quadratic model, conceived to optimize final topography according to the primary process and laser polishing. Based on an experimental matrix, the model takes into account both laser operating parameters and the initial topography, in order to predict polished surfaces and to determine an optimal set of parameters. Furthermore, uncertainties linked to the measuring device need to be taken into consideration, as well as the process variability, in order to facilitate the interpretation of the results. After the phase of experimentation and the creation of the quadratic model, an optimal final topography is introduced, taking into account the initial surface and the laser parameters. Finally, in order to reduce the time process, it is important to study the impact of laser polishing strategy on the surface roughness.

Depuis 1992, le SPCTS propose en téléchargement sur le réseau Internet (autrefois Minitel) la base de données et de calculs thermochimiques T&TWinner (Thermodynamique & Transport sous Windows). Ce logiciel convivial et ergonomique permet à tous de simuler les réactions chimiques à l'équilibre thermodynamique. Les algorithmes de calculs utilisés, ont été choisis en raison de leurs robustesse, précision et rapidité afin d'évaluer les propriétés thermodynamiques de systèmes complexes ou les coefficients de transport de la phase gazeuse. Ceux-ci estiment ainsi de façon particulièrement performante les nombres de moles d'espèces extrêmement minoritaires, ce qui est précieux pour prévoir la présence de traces toxiques dans les processus de synthèse chimique ou de pyrolyse. Un bilan de flux de grandeurs échangées peut être effectué, après le calcul des coefficients des grandeurs de transport. Ainsi la viscosité représente les échanges de quantité de mouvement, la diffusion représente les échanges de matière et la conductivité thermique les échanges de chaleur.

In this paper, railway-induced ground vibrations are analysed experimentally with the aim of addressing questions raising from the planning of a new RER network, available in the near future in order to alleviate pollution and the traffic jams. Free field ground vibrations are measured during the passing of InterCity and InterRegion trains. Various sites along the main line L161 Brussels-Luxembourg are chosen and investigated, with specific differences about the track and soil configurations. In order to compare these results with numerical ones, a deep dynamic characterisation of the track, the soil and the train is first performed. The analysis of horizontal and vertical ground vibrations measured during the passage of domestic trains (AM96, AM86, AM80, AM75, HLE27/M4 or M5) at various speeds (from 40 to 120 km.h-1) is then presented. The results show that the ground vibration amplitude depends on various factors: soil configuration, train type and speed, direction of measurement, track quality. In a particular case, a local defect (rail joint) induces large deformations of the soil.

The market demand for machining and cutting of various plastics parts is in continuousincrease. The aim of this study is to extract prediction laws for surface roughness,cutting forces and temperatures evolution during the machining of two polyethylene pipesgrades (HDPE-100) and (HDPE-80). It was found that feed rate is the most prevailing factoron roughness criteria and that better surfaces are obtained during the machining of theharder HDPE-80 resin. Also, cutting speed improved surface quality for speeds up to 200m.min-1 but the rising interface temperature caused surface damage andmaterial rapid softening. Also, feed exponents, in mathematical models, were found to be 3to 4 times higher than those of cutting speed and depth of cut. An increase in the cuttingspeed led to a gradual reduction for the 3 cutting forces components (Fr,Fa and Fv) with a dominance of the tangential force(Fv). As expected, the value of the depth of cut had a large influenceon the temperature within the cutting zone. This temperature is slightly higher during themachining of HDPE-80 compared to that of HDPE-100 most probably because of hardnessdifferences. The analysis of variance (ANOVA) was performed to check the adequacy of themathematical models relating cutting parameters with roughness, cutting forces and globalcutting zone temperature.

This paper investigates the windage power losses generated by spur gears rotating in pureair by using a computational fluid dynamics (CFD) code. The three-dimensional simulationsare at first validated comparing CFD predictions with the power losses measured in similarconditions from other investigations. The volumetric flow rate which is expelled by theteeth is then analysed, and a correlation which is based on a classical approach used inturbomachinery is finally proposed which makes it possible to estimate windage losses forspur gears. It was observed that this latter approach seems satisfying since theformulation of the volumetric flow rate which is employed in the model is appropriate toeach gear.

Tilting-Pad Journal Bearings (TPJB) are commonly used on high-performance turbomachinerydue to their excellent stability properties at high speed when compared to other designsfor oil film bearings. Hence, efforts have been made to improve the accuracy for theavailable models for these mechanical devices, achieving nowadays anelasto-thermo-hydrodynamic formulation. On the other hand, the basic design of theTilting-Pad Journal Bearing has been modified in order to transform it into a smartmachine element. One approach to do so is to inject pressurized oil directly into thebearing clearance through holes drilled across the bearing pads. By adjusting theinjection pressure, it is possible to modify the dynamic characteristics of the bearing. Acontrollable lubrication regime is obtained, allowing to expand the operational boundariesof the original design. This work focuses on presenting an elasto-thermo-hydrodynamicmodel (ETHD) for the Tilting-Pad Journal Bearing, including the effect ofthe controllable lubrication system. The basic model is validated by comparing its resultsagainst theoretical and experimental results available in the literature. Then, thevalidated code is used to show the benefits of applying a controllable lubrication regime,by means of the modification of the thermal and dynamic behaviour of the bearing.

Vibrations in buildings impact the behaviour of structures and humans, for sourcesdefined as internal or external to the building. Besides the comparison of vibrations tofixed limits, the choice of a relevant indicator is unavoidable and this indicator isdefined differently according to the selected reference text. Various standards (ordirectives similar to standards) exist and this paper focuses on the most important andthe most used ones, for ground vibrations induced to buildings or for human exposureinside buildings. In addition to the interest of comparing values to well-defined andwell-known limits, the knowledge of these standards allows the use of suitable indicators.Various vibration signals are used, from a simple harmonic signal to complex vibrationsgenerated by railway traffic, in order to present a relevant analysis of severity of eachnorm. It turns out that criteria noticeably vary from one reference to another one, andthat the thresholds are different for each standard.

La modélisation d'une transmission par engrenages simple étage en mouvement permanent par un système à 2 degrés de liberté a permis de mettre en évidence un mode de corps rigide et un mode élastique. Le mode de corps rigide traduit la condition cinématique de roulement sans glissement et la condition de transmission de mouvement. Le mode élastique est la conséquence directe de l'élasticité des dents qui est à l'origine de l'erreur de transmission. La variation périodique de la raideur d'engrènement lors de la rotation constitue une source d'excitation interne pour la transmission. La détérioration d'une ou de plusieurs dents affecte la raideur d'engrènement et influe par conséquent sur le comportement dynamique de la transmission. Le but de cette étude est de simuler un type de défaut localisé sur une ou plusieurs dents ou bien réparti sur toutes les dents de façon à décrire approximativement un début de fissure, un écaillage, ... L'analyse de la réponse dynamique a permis alors de déterminer qualitativement l'influence de ce défaut. Des méthodes de détection appropriées au type de défaut sont utilisées. Il s'est avéré que pour les défauts localisés, la méthode du cepstre est très utile tandis que la méthode spectrale reste valable pour les défauts répartis.

In this study, effects of surface modification of calcium carbonate (CaCO3) nanoparticles with a single-layer of stearic acid were investigated on dispersion in polypropylene (PP) matrix. Two kinds of CaCO3 nanoparticles (monolayer-coated and uncoated) were used to investigate this effect. All combinations were mixed in a co-rotating twin screw extruder and then were injection molded. After breaking the injection molded parts in liquid nitrogen, effect of surface modification of nanoparticles on their dispersion in the PP matrix was investigated using a field emission scanning electron microscope (FESEM). The results showed good agreement between the measurements made with the TGA analysis and the existing theories. The surface modification of calcium carbonate nanoparticles using a single layer of stearic acid also had an effective influence on improving distribution and dispersion of nanoparticles in the PP matrix.