Magnetic bearings are oil-free bearings that are widely employed in turbo machineries such as turbo refrigerant compressors in order to eliminate lubrication systems, avoid contamination, and increase efficiency. We have developed a 145 refrigerant ton (RT)-class turbo refrigerant compressor using homopolar-type radial hybrid magnetic bearings (HMBs) and thrust magnetic bearings. The thrust magnetic bearing comprises a thrust HMB and a permanent magnet that generate downward forces to overcome high upward thrust forces of 2000 N at 21 000 rpm. A test rig and controller for the compressor with magnetic bearings were fabricated, and rotordynamics such as the unbalance response and axial displacement were investigated. Rotordynamics analyses using the finite element method predicted that the 1st bending mode is located at a high frequency with sufficient margin from the operating speeds. Further, the zero-to-peak displacement caused by the unbalanced response was sufficiently small. The rotor was stably supported with few vibrations across the entire range of the operational speeds. Our results demonstrate that the advantages of oil-free bearings can be easily exploited in turbo machineries such as turbo refrigerant compressors by adopting HMBs.

Impeller tip clearance is a key parameter in design process of a centrifugal compressor which has influential effects on its aerodynamic and thermodynamic performances. Interaction of tip leakage flow with the main stream could be the major source for occurrence of stall phenomenon. In the present investigation, two impeller tip clearances of small and large sizes are investigated under different flow coefficients assigned to “design”, “low flow” and “high flow” conditions. Flow field is precisely simulated utilizing solution of the Reynolds-Averaged Navier-Stokes equations. Influence of the impeller stall on the volute flow field is studied. Structure of vortical flows within the impeller passages and volute are demonstrated in details. Numerical results showed that the flow within the volute becomes stall-prone while the flow within the impeller stalls. In contrast to the high flow case, the low flow condition was more prone for the stall occurrence. Performance tests were also conducted on Iran University of Science and Technology (IUST) centrifugal compressor test rig for validation of the numerical results.

Subsystems of rotary-wing aircrafts, such as helicopters for instance, are strongly interrelated due to their intrinsic specificities. Convergence to a feasible design is then not ensured and implies an iterative process. Moreover, rotorcrafts must cover a much wider range of missions than their fixed-wing counterparts. For those reasons a correctly sized rotorcraft is difficult to obtain and finding the best design for a defined set of missions needs numerous iterations. This article presents the application of a multi-objective optimization approach from the predesign stage. The standard predesign approach has been reformulated to highlight sizing constraints and three strategies are then proposed to solve those constraints: the first one is the basic transcription of the standard predesign approach; the second one leaves the problem solving to the genetic optimizer through penalization; the third one is a hybrid of both previous methods based on a constraint repairing approach. Those strategies also involved the adaptation of the helicopter modelling. Here, the focus is on two components of that new model: namely the main rotor polar and the weight assessment model.

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.

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.

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.

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.

In this paper, we consider the possibilities of the stimulated infra-red thermography for local metallic sample thermal characterization. At first we introduce the measurement principle, which is based on the local measurement of the thermal diffusivity parameter. Then, using simulations, we demonstrate the feasibility of the method. We then present the experimental device implemented for the study. Finally, we show that this approach allows a good estimation of the thermal diffusivity of a metal sample.

In this work, we approach the possibilities of infrared thermography for non-destructive testing of metallic materials. We show that the passive alternative of the method makes it possible to improve detection of surface defects existing in deep-drawn parts and visible to the naked eye. We then show that active infrared thermography, in particular coupled with induction excitation, can replace in certain cases the magnetic particle inspection, allowing the detection of very fine defects in forged parts. Finally, the study of a stepped block confirms the possibilities of active infrared thermography to detect defects not open to the surface and underlying defects.

The measurement of the thickness of a coating layer is a traditional industrial problem. Many methods of measurement are already classically used for that purpose. However, the majority of these methods require either contact with the sample to be studied, or its destruction. These constraints limit their applicability. Photothermal radiometry is already largely used in the field of thermophysical properties measurement and for the detection and characterization of defects. This method does not impose the constraints mentioned above. It could thus be a complementary technique of the classical ones. The purpose of this work is then to approach the possibilities of this photothermal method, implemented under pulse excitation and front face analysis, for the measurement of the coating thickness. Using theoretical and experimental studies, we show that the method allows a good estimation of the thickness of chromium deposits on a steel substrate, at distance, without contact and in a non-destructive way.

Cet article porte sur une méthode d’estimation, novatrice et non intrusive, de la conductance thermique de contact dans un mur de réacteur métallurgique. Dans le cas d’un réacteur métallurgique, il est essentiel de déterminer la conductance thermique de contact dans l’assemblage des parois. Cela permet d’identifier et de corriger les défauts de contact avant la mise en fonctionnement du réacteur métallurgique. Cette étude recourt à la méthode inverse du gradient conjugué avec un problème adjoint, pour réaliser cette estimation. La méthode a été validée à l’aide de tests numériques représentant un diagnostic du contact thermique entre une paroi réfractaire et une paroi d’acier du réacteur métallurgique avec différentes conductances thermiques de contact. Dans un second temps, des tests supplémentaires ont été réalisés pour observer l’évolution de l’erreur d’estimation en fonction de deux nombres sans dimension, le rapport de conductivité thermique et le nombre de Biot. Cela a permis de conclure qu’il faut avoir simultanément un rapport de conductivité thermique supérieur à 1 et un nombre de Biot supérieur à 0,005 pour obtenir une estimation précise dans les cas étudiés.