This paper presents the analysis of the instabilities inception in a transoniccentrifugal compressor for different rotation speeds. The analysis was conducted fromexperimental results obtained with unsteady pressure sensors implanted in the inducer,vaneless diffuser and vaned diffuser. Beyond the stability limit the compressor entersinto a deep surge without any precursor, whatever the speed. The surge process isinitiated in the vaned diffuser by a massive boundary layer separation. For low speeds,together with the surge which remains triggered in the diffuser, aerodynamic instabilitiesare detected in the inducer. These instabilities can be understood as “tip clearancerotating disturbances” because they are generated at the leading edge of the impeller mainblades and move along the tip clearance trajectory.

Showerhead cooling process which consists of internal convective cooling and externalfilm cooling of a turbine blade is investigated using ANSYS-CFX software. The aim of thepresent investigation is to provide a better understanding of the fundamental nature ofshowerhead cooling using the three dimensional Reynolds averaged Navier Stokes analysis. Anumerical model has been developed to study the effects of coupled internal and externalcooling of the leading edge for a semi-elliptical body shape with the SST k-ω model. This modelconsists of all internal flow passages and cooling hole rows at the leading edge. Thenumerical results obtained are discussed and compared with experimental data available inthe literature. The results show that the cooling efficiency increases with the increaseof the blowing ratio and the Mach number, therefore, the overall efficiency for the steelbecomes less important compared to the plexiglas which has a low thermal conductivity.

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.

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.

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.

Cleavage fracture anisotropy has been studied on a ferrite-bainite low alloy pipeline steel plate. Mechanical tests have been performed on smooth and notched bars taken along the three principal directions of the plate at temperatures between 20 °C and −196 °C, and analyzed by finite element calculations with an anisotropic plasticity model. The fracture mode of specimens tested along the normal direction differs from that of specimens taken along the two other directions, together with a lower critical cleavage stress. This difference seems to be related to microtexture anisotropy and might explain the sensitivity of this steel to delamination at low temperatures.

This paper falls within the context of diagnosis of rotating machines in speed variableregime. Based on simulation signals, this work has the purpose to find relevant indicatorsfor the diagnosis of gear transmissions in a variable regime. Two indicators are proposed;the first indicator is the RMS value applied to the vibration signal divided by itscorresponding instantaneous frequency. The second is the normalised gear frequency byaveraging speed. The gear frequency and averaging speed are estimated from thespectrogram. To test the proposed indicators simulate signals have been used. Thesesignals are the results of a dynamic modelling of the gears transmission and arecalculated by using the Newmark integration diagram. This dynamic modelling takes intoaccount the eccentricity defect.

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.

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.

The finite element analysis of the behaviour of airframes subjected to crash or impactloadings requires the use of suitable finite elements, in particular for the modelling ofriveted assemblies. In order to predict the structure survivability, it is indeednecessary to focus on these areas because stress concentrations, and consequently crackinitiations, which can lead to catastrophic loss of the airplane, are likely to occur.Because of the local nature of the phenomenon, the disproportion between the aircraft andthe assembly scale, and the large number of fasteners in a complete structure (more than100 000), super-elements for the fasteners and for the perforated sheets have beendeveloped in order to suitably model assemblies in structural calculations. However, thesetwo types of finite elements can not be currently connected together. The paper presentedhere focuses on how to link these finite elements.

Today, to cope with the complexity of the global organization, the industrial companyneeds to be more structured. New processes have to be developed due to more and moreambitious quality requirements. A new problematic arises: what is needed to offer to allcustomers a product that meets the quality requirements of a local market? The mainobjective of this paper is to propose a quality requirements allocation method thatmatches the market specifications and the customer satisfaction. This is in contrast withthe traditional allocation methods which are often time-consuming to implement or do notfocus on the customer satisfaction for the definition of the quality targets. The proposedmethod is inspired from reliability allocation method and is formulated as a feasibilityproblem. In this context the notion of optimality of the solution is not being sought, theobjective is “only” to find out a solution that satisfies the global target quality. Thisallows determining some local quality targets in accordance with industrial data.

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.

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.

Vibration analysis is the most widely used tool in industrial application for machine’shealth condition assessment. Bearings, however, are very sensitive and require specialattention. Vibration analysis employs various signal processing methods such as spectralanalysis, time-scale, time frequency analysis, etc. these methods are used to analyzebearings’ vibratory behavior by monitoring the evolution of statisticalindicators.However, diagnosing the bearing depending on traditional features only isn’tsufficient to assure effective or reliable assessment of the component’ health condition.This paper proposes a multi-features online dynamic classification as a new method forfault detection and health condition monitoring for bearings; this technique uses multiplefeatures, including traditional features extracted from the raw signal, two specialfeatures extracted by wavelet analysis, the spectral kurtosis, coupled with a nonlinearprincipal component analysis and a dynamic classification to capitalize on the hiddeninformation in the time evolution of the features.Through this article, we introducedifferent measures and techniques used to characterize the health state of rolling, thenwe deploy a methodology using dynamic classification to detect early defect. To ensure analmost continuous surveillance, this methodology is based on a real-time analysis, anduses specific statistical indicators adapted to the experimental bench. Then, themonitoring of the degradation is achieved through the resulting class of the state ofdegradation. New parameters such as the speed of the class, the position of the class, theshape of the class will be discussed to inform the state of damage. The suggestedmethodology is validated by analyzing several fatigue tests from a fatigue bench bearingthrust ball referenced SNR51207.

The use of composite laminates is increasing in these days due to desired directional properties and low densities in comparison of metals. Delamination is a major source of failure in composite laminates where a crack like entity can initiate and propagate between different layers of composite laminates under given loading conditions. Damage mechanics based theories are employed to simulate the delamination phenomena between composite laminates. These damage models are inherently local and can cause the concentration of stresses around the crack tip. In the present study integral type non-local damage formulation is proposed to avoid the localization problem associated to damage formulation. A comprehensive study is carried out for the selection of different non-local variables. Finite element simulations based on proposed non-local damage models and classical local damage model are performed and results are compared with available experimental data for UD IMS/924 Carbon/fiber epoxy composite laminate.

This paper presents closed loop simulation of a CMOS-MEMS force sensor for biomedicalapplications employing an optimal proportional-integral-derivative controller. Since thedynamic behavior of the sensor under investigation is nonlinear the iterative feedbacktuning approach was proposed for optimal gains tuning of the proposed controller.Simulation results presented in this research illustrate that the proposed controllersuppresses the undesired in-plane vibration induced by environment or gripper 40 timesfaster than the nonlinear controller proposed in the literature. To suppress the maximuminput disturbance the maximum voltage was approximately 18 V which was less than thepull-in voltage of 30 V. The proposed controller is served to actuate two stator fingersadjacent to a rotor finger in order to provide both the attractive and repellent forcesduring manipulation. Employing the proposed mechanism not only resolves the drawbackscorresponding to the nonlinear controller presented in the literature but also improvesits performance of the closed loop system by using the complete nonlinear dynamics of theforce sensor. Also, applying complete non-linear dynamic of model improves the performanceof controller and is one of superior features of proposed PID controller in comparisonwith the classical controller presented in literature.

The fuel handling operating rules exclude any accidental risk. However in the framework of the PRECCI R&D project, the bending of a spent fuel assembly resulting from its locking during a translation displacement is taken into account. This enabled us to develop an approach based on experiments and calculations that allows us to simulate the behaviour of an assembly under such loading. This study was carried out in CEA laboratories with the funding and the technical support of EDF. A three points bending test on a spent fuel rod segment was performed at the Laboratory for Mechanical Behaviour of Irradiated Materials (LCMI). From the experimental strength-displacement curve, a maximum failure strain, a maximum failure curvature and an equivalent constitutive equation were determined. CAST3M modelling of the fuel rod taking into account the elasto-plastic behaviour of the clad and the cracking of the UO2 fuel pellets was verified by the experimental results. Consequently, the identification of the respective contributions of the clad and of the pellets to the rod global behaviour was made possible. A two dimensional assembly with beam elements was modelled with CAST3M. The properties of the beams modelling the different parts of the assembly (top and bottom nozzle, grids) were chosen and adjusted according to their materials (zirconium alloys, steel) in order to obtain stiffness, tensile and shear behaviour, sliding and holding functions close to the experimental ones. Assembly bending calculations were performed. In order to obtain a rod integrity estimator, their maximum calculated strains and curvatures as a function of the bending angles can be compared to the failure experimental ones.

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.

This study focuses on the phenomenon of oil trapping in the tooth spaces of spur gears.It presents the first obtained results in order to provide an estimation of the powerlosses due to the compression of the oil trapped between the inter teeth meshing spaces ina high-speed transmission for internal and external spur gears. It first allows, to modelthe inter teeth spaces at any time and offers limits for the trapped fluid volume andaxial and radial discharge surfaces. The discretization impact result is discussed.Then,the influence of certain design and operating parameters such as module, pressure angle,addendum modification coefficient and rotational speed on these discharge surfaces andtrapped volume is presented.

In this paper we present the design of a compact active cardiac stabilizer based onplanar compliant mechanisms and piezoelectric actuators. Considering an assembly of planarmanufactured structures helps to simplify the manufacturing process and may increase thecompactness. Parallel architectures constitute interesting solutions for their intrinsicstiffness properties, but in a planar configuration parallel manipulators often exhibitkinematic singularities. Two design approaches for planar parallel compliant mechanismsare presented in this paper. One design approach consists in designing a passive compliantmechanism in a configuration close to the singularity by introducing some asymmetriesduring the manufacturing process. The second design approach consists in taking advantageof the singularities of parallel manipulators to obtain non-trivial solutions. The newproposed active stabilizer, composed of planar compliant mechanisms, is introduced and itsperformances are discussed.