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.

Shape memory alloys (SMA) are good candidates especially for being used as passivedampers. In order to develop the use of these alloys in structural vibrations control, thedynamical behavior of a NiTi helical spring is led, and the damping effect investigated.First, compression tests on the spring are carried out. These tests allow us to notice theeffect of the maximal compression displacement, the cyclic behavior and the compressionrate on its mechanical behavior. A finite element model analysis of the compression testsis then proposed. In consequence, the materials parameters have been identified after anumerical convergence test. In order to characterize the dynamical behavior of the spring,the innovative tool called equivalent complex stiffness is developed and used. Finally,the one degree of freedom vibration equation is solved with this equivalent complexstiffness. The solution of this equation clearly shows the non linear dynamical behaviorof the SMA spring and its damping potential.

L’usinage robotisé, nouveau challenge de la robotique industrielle, nécessite à la fois rigidité et précision du moyen de production. C’est pourquoi cette pratique particulière du détourage des composites était réservée jusqu’alors aux machines-outils à commande numérique. Cet article propose de démontrer, qu’à partir d’une connaissance des phénomènes de coupe liés aux procédés et de la modélisation des caractéristiques comportementales du robot, il est possible d’optimiser l’exploitation des cellules robotisées. Cette première étude porte sur le cas spécifique du détourage des pièces composites. D’un côté, le robot a été modélisé et ses paramètres de raideur ont été identifiés. De l’autre côté, les conditions de coupe optimales permettant de respecter l’intégrité matière et d’assurer la productivité souhaitée ont été déterminées. Les efforts d’usinage ont alors été relevés. À partir de ces deux études parallèles, les déformations du robot, pour un placement donné de la pièce dans son espace de travail, ont pu être déterminées. Par la suite, ces déformations peuvent être limitées en plaçant judicieusement la tâche dans le volume de la cellule robotisée. Cette solution simple permet de réduire significativement les déformations observées, notamment dans le cas de procédés sollicitant fortement le robot, et ce sans modifier sa commande.

The aim of this study is to approach the possibilities of stimulated infraredthermography to the carpal tunnel syndrome diagnosis. Eleven patients were studied. Six ofthem were affected by the carpal tunnel syndrome. The five others were healthy. The studyconsists in exciting the patients’ hands and in analyzing their thermal response. Theinfrared thermograms obtained show that the hands infected by the carpal tunnel syndromegive a different thermal response.

La compréhension du phénomène de la rupture des matériaux nécessite des études approfondies des phénomènes d'amorçage et de propagation des fissures qui, en général, prennent naissance dans les zones de fortes concentrations de contraintes dues aux effets géométriques ou métallurgiques. La connaissance de la distribution des contraintes au voisinage des différentes zones a une importance pour l'analyse de la variation du facteur de concentration de contraintes en fonction de leurs géométries. Ceci permet aussi d'expliquer le phénomène d'amorçage d'une rupture et de quantifier le facteur d'intensité de contraintes (FIC) en fonction de la géométrie de l'entaille et de la longueur de la fissure. Dans cette étude, on a essayé de modéliser par l'application de la méthode des éléments finis (MEF) l'effet de la présence d'une entaille et d'une inclusion sur le comportement d'une structure.

Une revue bibliographique étendue est réalisée sur le thème de l’usinabilité descomposites à matrice polymère renforcée par des fibres, dans le but de fournir desrésultats et conclusions sur l’usinage des matériaux composites à matrice thermoplastiqueet à fibres courtes. Un rappel sur l’état de l’art dans ce domaine, sur les spécificitésliées à l’usinage des composites organiques et sur les différents modèles ayant étéintroduits pour prédire les paramètres de coupe a été effectué. Les paramètres affectantl’usinabilité proprement dite des composites ont été revus, ensuite une richebibliographie sur le sujet est présentée. Enfin les critères d’usinage ont été présentéssous forme synthétique en considérant les différentes contributions développées dans cedomaine et, de manière presque exhaustive, toutes les références bibliographiquessignificatives ayant traité de ce sujet.

The objective of this article is to present the dimensional synthesis of serial andparallel spherical wrists, an important step in the design process of medical robots. Thisstep is carried out to obtain optimal dimensions of tool-guidance medical robots. Withthis goal, we have first studied the specifications of two robots with different medicalapplications: one for tele-echography examination and one for minimally invasive surgery.Then, we have established that the medical needs expressed by the doctors were verydifferent but the specifications in robotic terms have a lot of common points (kinematics,workspace, bulkiness). For both applications studied, robots need a mobility of threerotations around a fixed point (probe contact point on the patient’s skin or trocarincision). So, a spherical wrist architecture is adapted to their needs. An importantconstraint related to medical applications is that the robot must be compact in order tonot obstruct or collide with its environment (medical personnel or patient). We performdimensional synthesis allowing determination of dimensions of the mechanism for serial andparallel spherical wrists, for a tele-echography robot, and a serial wrist for a minimallyinvasive surgery robot. We use multi-criteria optimization methods minimizing a costfunction to obtain both good kinematic performance and compactness for the architecture.The difficulty/challenge of this design process, depending of the studied applications, isthe choice of efficient criteria describing the performances and the constraints of therobot. The design variables must faithfully represent the specifications of the robot sothat its performance can respond to the medical requirements. We show, here, the differentmethods used for optimizing the chosen kinematic architecture for the particular medicalapplication. These studies lead to prototypes which are validated after medicalexperiments. This process of dimensional synthesis will be applied to other medicalapplications with different sets of specified constraints.

Vibration and wear debris analyses are the two main conditions monitoring techniques for machinery maintenance and fault diagnosis. In addition, numerical simulation can provide useful tools to assess the proper functioning of industrial machines. We use different suspension theories with a concern of the effect of solid particles liquid lubricant itself on bearing behavior. We consider both simple models based on the Einstein’s mixture theory and a micropolar fluid theory, which is characterized by the presence of suspended rigid micro-structured particles. We suppose in this study that there are no abrasion and no wear (which are not beneficial for the contact performances) due to the presence of particles. Thus in this case we found theoretically that the presence of rigid particles in the lubricant increases the effective viscosity which enhances the load-carrying capacity as well as the minimum film thickness.

The present study deals with the thermal behavior of an electric motor used in navalpropulsion. A permanent three-dimensional model based on a nodal approach was developed topredict the thermal behavior of the machine in permanent state. The various heat transfermodes playing a role (mainly the conduction, the convection and the mass transfer) aretaken into account. The three dimensional developed model provides information (in termsof heat fluxes or temperatures) for the whole machine. A parametric study using this modelis carried out aiming at two objectives. The first one consists in an evaluation of theinfluence of several factors on the temperature distribution. The second one aims atobtaining the inception of the thermal optimization and evaluating the more efficientcooling techniques or solutions.

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.

Safflower is an oil-seed crop with high quality oil that is used for producing healthyfoods and painting colors. This crop has valuable petals which have a lot of uses inmedicine, production of food colors and dyes for coloring fabrics, but such problem asdispersion of flowers, thorns of crops that hurt worker’s hands also lack of a suitableharvesting machine have enforced farmers to harvest petals by hand that is a hard work andnon-economic. In this study a prototype machine was designed and constructed. This machineincludes an engine, a radial fan with BI blades, a snout, a diffuser to separate petalsfrom airflow and a store; all parts are assembled on a trolley to move easily in farm.This machine picks safflower petals out and intakes through snout by the fan suctionpower. Petals go to diffuser where they are separated from airflow then fall to the store.Velocity of airflow in the snout was determined by a fan test duct in order to designdiffuser. At last three farms were harvested by this machine for economic analysis.Results show 657% increasing in amount of harvested petals by harvester machine incomparison with hand harvesting.

This study presents a NDT method using infrared thermography associated with a microwave excitation. The advantages of such stimulation lie in the volumic absorption of incoming waves which lead to a greater sounded depth. This method is applied to two types of samples. The first is a concrete slab reinforced with CFRP on which a bonding failure is inserted and the second is a wooden plate on which a metallic insert is placed on the back face. The device generating the microwaves is made of a commercial magnetron associated with a pyramidal horn antenna. An infrared camera is placed on the same side as the stimulated surface and thermograms are recorded at regular intervals. The whole assembly is placed in a protective room against high frequencies. The incident power density leads to heating of less than 1 °C of the surface of the samples. The thermograms show a higher temperature rise in front of the defect area. The non-uniformity of the beam, leads us to treat the thermograms with an algorithm of contrast. These first results show the interest of the microwave excitation to detect defects deeper than in the case of surface excitation.

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.

Conventional methods (i.e. time, frequency and cepstrum) can routinely be used to revealfault-indicating information in the vibration signal. In recent years, wavelet analysis,which can lead to a clear identification of the nature of faults, is widely used todescribe rotating machine condition. The capability of this method in the detection of anyabnormality can be further improved when its low-order frequency moments are considered.This paper presents the use of the fast kurtogram in the early detection and conditionmonitoring of pitting fault. For this purpose, a dynamic model of a simple stage gearbox(with and without defects) is used. Then, the pinion’s vibration displacement is analyzedby using a fast kurtogram method. This method is suitable for such diagnosis and givesvaluable information about the presence and effects of the pitting tooth defect.

Dimensional errors of the parts from a part family cause the initial misplacement of theworkpiece on the fixture affecting the final product quality. Even if the part ispositioned correctly, the external machining forces and clamping load cause the part todeviate from its position. This deviation depends on the external load and the fixturestiffness. In this article, a comprehensive analytical model of a 3-2-1 fixturing systemis proposed, consisting of a kinematic and a mechanical part. The kinematic modelrelocates the initially misplaced workpiece in the machine reference through the axialadvancements of six locators taking all the fixturing elements to be rigid. Therepositioned part then shifts again from the corrected position due to the deformation offixturing elements under clamping and machining forces. The mechanical model calculatesthis displacement of the part considering the locators and clamps to be elastic. The rigidcuboid baseplate, used to precisely relocate the workpiece, is also considered elastic atthe interface with the locators. Using small displacement hypothesis with zero friction atthe contact points, Lagrangian formulation enables us to calculate the rigid bodydisplacement of the workpiece, deformation of each locator, as well as the stiffnessmatrix and mechanical behavior of the fixturing system. This displacement of the workpieceis then finally compensated by the advancement of the six axial locators calculatedthrough the kinematic model.

Today's businesses continually search for ways to increase productivity. To achieve this goal, shorter product development cycles and shorter manufacturing times are required. In both cases, problems that may arise during development must be identified much faster. In product development, this is done using virtual prototypes that can be easily duplicated and shared between everyone involved. In addition to this product design process, the stability of the manufacturing process and the resulting product quality ultimately determine the product's profitability. Therefore the manufacturing concepts of a new product can best be demonstrated using Virtual Manufacturing. The subset of Virtual Manufacturing where material properties of the product and machine tools and the physics of the process are investigated is called Virtual Process Engineering. Virtual Process Engineering utilizes Finite Element Methods (FEM) and simulations for the computation of the manufacturing process and Virtual Reality (VR) for quick and intuitive examination of the computation results.

Rotating machines monitoring in a non-stationary regime, characterized by the operating parameters (speed, load) variation, presents a particular challenge. The speed variation has an impact on the vibratory response given by the accelerometers and therefore masks any defect that may be detected by classical indicators (for example RMS value). To overcome this problem, a new indicator is proposed. For this, a signal accelerometer and a signal from an optical encoder are acquired simultaneously. An algorithm to estimate the instantaneous speed from the signal delivered by the optical encoder is applied. Then, each sample of the accelerometer signal is divided by its corresponding instantaneous speed sample. The RMS value is then applied to the resulting signal. A model simulation signal is used to test the proposed method. A test rig is performed to extract signals of different degradation states of thrust bearings in variable speed regime. The results show a correlation between the proposed RMS value and the thrust bearings state in variable regime.

This work is interested to the analysis of the vibratory signals coming from a millingoperation. The objective is the detection of cutting tool breakage using thecyclostationary tools. Initially, we will show that the vibration signals captured fromthe milling operation are cyclostationary. The proposed cyclostationary methods are thefirst and second order synchronous statistics and the spectral correlation. A test rig,composed of a milling machine (cutter with 5 teeth) and a workpiece, is used to extractthe vibration signals that are angular sampled in the free fault case and one broken toothcase. This test rig is instrumented with three accelerometers, installed in the threedirections, and an optical encoder that allows the angular sampling. Then we will see thatthe angular sampling of the signals captured from a milling operation is essential topreserve the cyclostationary properties destroyed, in the case of the temporal sampling,by speed fluctuations. The proposed method capacity to detect the broken tooth is shown.The synchronous statistics of order 1 and order 2 detect the broken tooth presence and itsemplacement. The spectral correlation analysis distinguishes the broken tooth presence,but is not practical for the diagnosis. For that, an indicator based on the spectralcorrelation is proposed.

Cette étude expérimentale présente l’étude du comportement mécanique d’un polyamide 66(PA66) renforcé par des fibres de verre courtes fréquemment utilisées dans l’industrieautomobile. Afin d’étudier l’influence de la teneur en humidité, de la quantité de fibresde verre introduite dans la matrice et de la vitesse de déplacement, une série d’essais detraction a été réalisée sur du polyamide renforcé ou non avec des fibres de verre courtesà différents fractions volumiques : 10, 20 et 30 wt%. Les résultats montrent la dépendancedu matériau aux différents paramètres cités précédemment. La technique de thermographieinfrarouge (IR) a été utilisée pour déterminer l’évolution de la température à la surfacedes matériaux au cours des essais de traction. Un processus de localisation de ladissipation thermique a pu être identifié à partir des images thermiques.

Thermoplastic based composites containing different weight fractions of molybdenumdisulfide (MoS2) solid lubricant were developed by injection molding.Polymethyl methacrylate (PMMA) and polycarbonate (PC) were chosen for the thermoplasticmatrices. In order to characterize the interfacial adhesion between the matrices and thefiller, we observed the fracture morphologies of selected composites. Micrographs of thefractured surfaces showed removal of MoS2 particles by microcraking as well asthe presence of voids in the case of PMMA/MoS2 composites. These observationswere confirmed by complementary images obtained using the X-ray tomography. The additionof an appropriate coupling agent may improve the adhesion between the MoS2particles and the polymer matrix. Tribological behavior of the composites was alsoinvestigated using a ball-on-flat microtribometer with a high chromium steel ballantagonist. It was found that the addition of MoS2 particles didn’t improve thetribological performance of the composite in the case of PMMA matrix unlike the case of PCmatrix where the friction coefficient was considerably reduced.