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.

Hydrodynamic journal bearings supporting high mass rotating machinery are subjected tolow rotational speeds during start-up or idling phases. These working conditions need ahydrostatic pressure contribution to ensure a correct load capacity when the hydrodynamicpressure is not established yet. This is possible by means of hydrostatic lift pockets.These pockets avoid mechanical damages via sufficient film thickness from start-up tohydrodynamic working conditions. In a first part, it is showed how an existing isothermal3D hydrodynamic numerical modelling of tilting pad bearing has been adapted to take intoaccount the lift pocket impact on static bearing performance. This approach is only validfor low rotational speeds, when inertia step pressure effects (rises or drops) at thefilm-pocket edge can be neglected compared to the total bearing pressure pattern. Then,numerical simulations have been performed, from 1 to 200 rpm with pockets and from 75 to200 rpm without pockets. The results have been compared and discussed in terms of pressurefields and bearing static performance such minimum film thickness, friction torque orrotor center position. Therefore, the interest of such lift pockets has been highlighted.Finally, calculations with and without pockets have been carried out in case of a strongbearing misalignment. As a result, the benefits of the lift pockets in this configurationare also significant in terms of static performance.

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...

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.

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.

Shrink fits are low-price connections which are widely used in industry and industrialconnections. In designing shrink fits it is important to consider radial interface foroptimized performance and also to choose an accurate method of fabrication and assembling.Parts which have to be assembled are usually exposed to thermo-mechanical loads. Mode andtime duration of heat transfer have a significant effect on required hydraulic force,stress time rate of creation in parts and joint ability to withstand against externalloads. Therefore, planning a set of appropriate thermal and structural procedures hassignificant role in reducing energy consumption, optimized performance and promoting thespeed of parts assembly. Despite of the fact, few researches have been done on shrink fitoperation and design, rather than dimensional design. In this study, shrink fits arestudied in two main processes: first heating and mounting process and then backing to theambient condition. A 3D coupled thermal and structural simulation based on FEM is done oneach process through well-known Solidworks Premium. To evaluate the accuracy, exactanalytical solution of two steel rings shrink fit is compared with the approach outcomes.Results of validated method are used for choosing the most optimum sub processes of shrinkfit fabrication.

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.

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.

This paper considers the effect of the damage caused by transverse stresses due to a low velocity impact loading on composite plates. The dynamic response of a plate is calculated using the modal superposition technique based on the classical plate theory of sandwich plates (stratified) taking into account transverse shear effects. An indentation law, based on the Hertz theory and verified experimentally, governs the behavior of the plate subsequent to impact. The numerical time integration scheme is used to calculate the contact force at any instant by combining the indentation and the dynamic response of the structure. The obtained results show a good correlation between the shock results and their prediction. This method is equally applied to the contact force as well as to the deformation of the plate. The simulation permits a parametric study of the structure dimensions and the material properties on the global behavior of the plate.

This work presents the dynamic modeling of ball bearing which uses multibody dynamicformalism. Such formalism allows immediate integration of the model in dynamic simulationsof helicopter main gear boxes. Ball bearing is considered non-lubricated in order topredict its behavior in case of lubrication system failure. Rolling contacts are treatedwith the method proposed by Kalker. This approach is based on polynomial approximation ofrelative displacement on the contact ellipse. For low computational cost and without anyspatial discretization, it gives a good estimation of tangential traction and creep. Also,a regularization of the Kalker linear creep theory is proposed. It is used here tofacilitate the global convergence of the Newton iterative process. It is well suited formultibody dynamic simulations which do not need a very fine treatment of rolling contact.A numerical example of a ball bearing under thrust load is presented.

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.

Early damage detection on structures plays a very important role for ensuring safety and reliability. This paper provides an efficient method based on wavelet transforms in order to detect and localize damage on structures subjected to moving loads such as beams and bridges. A numerical model based on the experimental test-rig utilized in this study is developed by using a finite element commercial software. Different types of damage on the bridge of the numerical model are simulated and transient analyses are performed by incorporating a load which moves constantly along the beam nodes. Continuous wavelet transform diagrams using the vertical acceleration responses show that damage can be identified and localized even with significant percentages of noise. Nevertheless, the method is improved by filtering the signals, removing the border effects, and calculating the total wavelet energy of the beam from the coefficients along the selected range of scales. Thus, the accumulation of wavelet energy could indicate the presence of damage. Finally, laboratory experiments are conducted to validate this work and a good agreement between numerical and experimental results is obtained.

The study aims at examining the behaviour of electromagnetic actuator as inductivesensor. The electromagnets are integrated in an alternative Wheatstone bridge and poweredwith alternative tension. This circuit allows the measurement of the electromagnetinductance variation, and as this variation is a function of the air gap, the displacementcan be deduced. The effect of eddy currents is assessed in order to choose the suitablebridge frequency. Finally, a demodulator is used to obtain the tension proportional to theair gap value. The behaviour is assessed experimentally. Experiments are carried out on asimple beam; clamped at one end and simply supported at the other. The displacements couldbe measured by using four eddy current sensors and the inductive sensor. The inductivesensor displacement and a modal approximation of the four eddy current sensors resultingfrom impact testing are compared. Analysis of the results obtained predicts an efficientand robust behaviour.

This paper presents an approach for obtaining an optimized geometry for the flank of atooth by minimizing the equivalent contact stress. The stress calculation method is basedon Hertz theory. As the majority of tooth profiles are involute, the geometric variationof the flank of the tooth is achieved variationally relative to the involute profile. Theoptimum profile is obtained by Monte Carlo simulation. During this optimization, apolynomial expression of the tooth geometry is used. The parameters influencing thesimulation are the four characteristic contact points. The approach presented has beenapplied in a representative case. A study of the geometric sensitivity was conducted onthe optimized tooth profile. Two different approaches were considered: by Monte Carlosimulation and analytical propagation. The robust and linear nature of the behavior of thetooth profile was demonstrated when it was subjected to geometric variations.

In order to improve digital mock-up, a tolerancing phase should be integrated in thegeometric models. However, in CAD software, tolerances are represented by annotations,which are neglected as well as the tolerance impact. Thus, the system malfunction isgenerated. For these reasons, in this paper a tolerancing phase is integrated in thenumerical model to form a realistic model, where worst case configurations of assembliesare determined from the tolerances assigned to the nominal model. The proposed modelincorporates tolerances on CAD models in the case of planar face, cylindrical face andplanar face with non quadratic loop. In addition, the model ability to respect the maximummaterial condition (MMC) and the requirement of datum priority order in the CAD models isshown. Finally, functional requirement of a linear guide mechanism is inspected by usingthe proposed model.

The dynamic response of a railway track under a moving train in the presence of adefective wheel is studied. The goal of this study is to establish an efficient dynamicmodel for wheel tread defect analysis. The wheel irregularities which influence the trackvibration characteristics are classified in 2 major types: periodic out-of-roundness andlocal defect. While the periodic irregularities are distributed all around the wheel, thelocal defects such as wheelflats have more impact on the dynamic response. The influenceof each defect depends on its geometrical characteristics and the model parameters. Theseparate effects of different irregularities have been the subject of many previousresearches. However the contribution of each defect to a coupling of irregularities wasnot as much considered. For a comprehensive analysis of all types of defects, an efficientglobal model is presented. It includes 3 sub-models for vehicle, contact force and track.The time-domain responses of the model are evaluated in comparison to those of a finiteelement model. It is shown that the semi-analytical model of the track keeps a goodprecision while being less time consuming. The results of the global model for differenttypes of wheel irregularities are presented.

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.

The paper deals with the assessment of the influence of morphological parameters of a 2Drandom short fibre composite on its effective elastic properties. A double-scale 2D finiteelement approach is used and periodic representative volume elements are generatedaccording to the model with an n-order approximate geometry. This one isa recent and powerful tool to generate meshes in the context of complex microstructuressuch as random fibre composites. Impact of three morphological features namely, aspectratio, tortuosity of fibres and width of the interphase area, is investigated. Numericalresults are provided for several contrasts of properties and volume fractions of fibres.

In this paper, we present the static and dynamic structural characterisation of alow-mobility parallel kinematic manipulator, involving analysis of its stiffness andvibrational dynamic behaviour. The study starts by building numerical models of thebehaviour of the manipulator to be compared to experimental measurements from a prototype.For the case study, we consider a four-degree-of-freedom(x, y, z, θz) manipulatorwith prismatic actuators designed by the COMPMECH research group at the University of theBasque Country. The characterisation allows the behaviour of the static and dynamicstiffness, as well as the natural frequencies of the manipulator, to be mapped in themanipulator workspace. These maps together with kinematic, static and dynamic constraintslead to the definition of operational, static, dynamic and structural workspaces,respectively. Further, we analyse the modes of the manipulator to determine dynamicdisplacements, these being key in the performance in the machining tasks for which therobot was designed.