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

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

Most of the norms used in the field of digital image (and volume) correlation to register two images (or volumes) lead to ill-posed problems. One of the frequent solutions is to enforce a restricted kinematics requiring a compromise between the richness of the solution (i.e., the spatial resolution) and the measurement uncertainty. An alternative route is to use a displacement norm that permits to alleviate this compromise by the means of 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 or voxel, inducing lower residuals (in terms of experimental data) while decreasing the noise sensitivity. The resolution performance of these different approaches is discussed, and compared for the analysis of a tensile test on a cast iron specimen based on a pair of tomographic images. As representative reconstructed volumes lead to a large number of degrees of freedom, a dedicated GPU computational strategy has been developed 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.

This paper presents the application of new time frequency method, ensemble empirical mode decomposition (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 it was recently proposed by Huang and Wu to overcome the drawbacks of the traditional empirical mode decomposition (EMD). The vibration signal is usually noisy. To detect the fault at an early stage of its development, generally the residual signal is used. There exist different methods in literature to calculate the residual signal, in this paper we mention some of them and we propose a new method which is based on EEMD. The results given by the different methods are compared by using simulated and experimental signals.

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 designing hydrodynamic water-lubricated step thrust bearings. The numerical analysis is undertaken under the condition of different pad dimensions, step heights, step positions, water film thicknesses and rotational speeds of thrust rings based on computational fluid dynamics (CFD). The results including pressure distribution, load carrying capacity, friction torque and friction coefficient are gained and compared for optimizing geometry parameters. A reference to determine water-lubricated step thrust bearing dimensions and a formula to check the minimum water film thickness are proposed.

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.

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.

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.

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

In this study, the dynamic analysis of Pipeline Inspection Gauge (PIG) flow control in natural gas and liquid pipeline is considered. The basic equations are differential forms of the mass and linear momentum for compressible liquid and gas flows. The fluid flow equations and a linear momentum equation of the PIG are solved simultaneously using an appropriate numerical method. Solution of these nonlinear equations results in a set of diagrams for the variations of the fluid pressure, mass flow rate of the gas and the PIG velocity through the pipeline. Comparing the results of mathematical model for the PIG with the established experimental data in a segment of Ahwaz gas pipeline shows a good agreement between the measurements and computations.

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.

Tilting-Pad Journal Bearings (TPJB) are commonly used on high-performance turbomachinery due to their excellent stability properties at high speed when compared to other designs for oil film bearings. Hence, efforts have been made to improve the accuracy for the available models for these mechanical devices, achieving nowadays an elasto-thermo-hydrodynamic formulation. On the other hand, the basic design of the Tilting-Pad Journal Bearing has been modified in order to transform it into a smart machine element. One approach to do so is to inject pressurized oil directly into the bearing clearance through holes drilled across the bearing pads. By adjusting the injection pressure, it is possible to modify the dynamic characteristics of the bearing. A controllable lubrication regime is obtained, allowing to expand the operational boundaries of the original design. This work focuses on presenting an elasto-thermo-hydrodynamic model (ETHD) for the Tilting-Pad Journal Bearing, including the effect of the controllable lubrication system. The basic model is validated by comparing its results against theoretical and experimental results available in the literature. Then, the validated 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.

Virtual reality shows to be of use in several domains of manufacturing as a complementary tool to CAD/CAM environment. Design review is one of the very first application of VR in product design, but assembly/disassembly studies are also existing though they require some more specific work. But it can also be useful beyond the scope of common CAD software such as ergonomic studies. We will show an example from the RNTL PERF-RV project where we study the ergonomics of a car dashboard and more specifically of a push-button. We will discuss the issues raised by studying ergonomics thanks to Virtual Reality and force-feedback systems which are both hardware and software.

The market demand for machining and cutting of various plastics parts is in continuous increase. The aim of this study is to extract prediction laws for surface roughness, cutting forces and temperatures evolution during the machining of two polyethylene pipes grades (HDPE-100) and (HDPE-80). It was found that feed rate is the most prevailing factor on roughness criteria and that better surfaces are obtained during the machining of the harder HDPE-80 resin. Also, cutting speed improved surface quality for speeds up to 200 m.min-1 but the rising interface temperature caused surface damage and material rapid softening. Also, feed exponents, in mathematical models, were found to be 3 to 4 times higher than those of cutting speed and depth of cut. An increase in the cutting speed 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 influence on the temperature within the cutting zone. This temperature is slightly higher during the machining of HDPE-80 compared to that of HDPE-100 most probably because of hardness differences. The analysis of variance (ANOVA) was performed to check the adequacy of the mathematical models relating cutting parameters with roughness, cutting forces and global cutting zone temperature.

This paper investigates the windage power losses generated by spur gears rotating in pure air by using a computational fluid dynamics (CFD) code. The three-dimensional simulations are at first validated comparing CFD predictions with the power losses measured in similar conditions from other investigations. The volumetric flow rate which is expelled by the teeth is then analysed, and a correlation which is based on a classical approach used in turbomachinery is finally proposed which makes it possible to estimate windage losses for spur gears. It was observed that this latter approach seems satisfying since the formulation of the volumetric flow rate which is employed in the model is appropriate to each gear.

In order to overcome the loss of performances issue when scaling resonant sensors down to NEMS, it proves extremely useful to study the behavior of resonators up to large displacements and hence high nonlinearities. A comprehensive nonlinear multiphysics model based on the Euler-Bernoulli equation which includes both mechanical and electrostatic nonlinearities in the case of a capacitive doubly clamped beam is presented. This purely analytical model captures all the nonlinear phenomena present in NEMS resonators electrostatically actuated including bistability, multistability which can lead to several physical limitations such as noise mixing, frequency stability deterioration as well as dynamic pull-in. Moreover, close-form expressions of the critical amplitudes and pull-in domain initiation amplitude are provided which can potentially serve for NEMS designers as quick design rules.

This study presents a finite element (FE) model of the human hand-arm system to derive natural frequencies and mode shapes. The FE model is calibrated by considering modal parameters obtained from experimental vibration analyzed by using operational modal analysis (OMA) and transmissibility. Modal and harmonic analyses of the FE model are performed for two boundary conditions. The first one considers fixed shoulder condition while the second one introduces the trunk in order to permit motion of the shoulder. The results show that the natural frequencies of the second model that permits shoulder motion are comparable with those determined from measurements. Especially, the natural frequency about 12 Hz, which is corresponding to the frequency of maximum weight in ISO-5349-1 (2001), is not present in the model with fixed shoulder condition, while it appears in the second model. The results of the present study suggest that improved finite element models of the human hand-arm system may reveal hand-arm injury mechanism, the understanding of which may assist in deriving appropriate frequency weightings for the assessment of different components of the hand-arm vibration syndrome.