A Method for Measuring Normal and Shear Stiffness of Laminate Stacks of Electric Motors

Structural simulations of electric motors require precise material models. Laminate stacks that are made of several identical steel sheets are particularly challenging to simulate using FEA. The structural stiffness of laminate stacks usually follows transversal isotropic behavior. Measuring a complete laminate stack used in passenger cars is challenging due to its size and the high testing load needed to reach real loads experienced while in operation. A new method capable of performing such measurements is presented in this article, with the help of equipment normally used for testing structures used in civil engineering. Two sets of exemplary results are presented utilizing this measurement procedure, that were performed on a real automotive rotor laminate stack: axial compression stiffness from a cyclic test, and shear stiffness at various axial preload levels. In the axial compression load case, the loading and unloading curves form a hysteresis, that changes in every test cycle. Shear stiffness shows high dependance on the axial compression preload. After loading and unloading the stack with shear loads, significant plastic deformations remain

Approche multiphysique pour la simulation du bruit rayonné par un transformateur : prise en compte des effets magnétostrictifs

Ce papier présente une approche multiphysique pour estimer le bruit rayonné par un transformateur en réponse aux excitations électromagnétiques. La méthode compte 3 étapes : il s'agit tout d'abord de calculer l'induction dans le circuit magnétique. Les effets magnétostrictifs sont alors pris en compte grâce à une analogie thermique et les réponses dynamiques de la structure peuvent être calculées. Le rayonnement acoustique est ensuite estimé par éléments finis acoustiques ou par une méthode analytique. Une démarche expérimentale, analyses modales et réponses en fonctionnement, permet de valider la méthode de simulation

Human olfactory receptor 17-40 as active part of a nanobiosensor: A microscopic investigation of its electrical properties

Increasing attention has been recently devoted to protein-based nanobiosensors. The main reason is the huge number of possible technological applications, going from drug detection to cancer early diagnosis. Their operating model is based on the protein activation and the corresponding conformational change, due to the capture of an external molecule, the so-called ligand. Recent measurements, performed with different techniques on human 17-40 olfactory receptor, evidenced a very narrow window of response in respect of the odour concentration. This is a crucial point for understanding whether the use of this olfactory receptor as sensitive part of a nanobiosensor is a good choice. In this paper we investigate the topological and electrical properties of the human olfactory receptor 17-40 with the objective of providing a microscopic interpretation of available experiments. To this purpose, we model the protein by means of a graph able to capture the mean features of the 3D backbone structure. The graph is then associated with an equivalent impedance network, able to evaluate the impedance spectra of the olfactory receptor, in its native and activated state. We assume a topological origin of the different protein electrical responses to different ligand concentrations: In this perspective all the experimental data are collected and interpreted satisfactorily within a unified scheme, also useful for application to other proteins.Comment: 6 pages, 6 figures, DOI:10.1039/c1ra0002

Model reduction of electric rotors subjected to PWM excitation for structural dynamics design

International audienceRotors of asynchronous machines can be subjected to risk of failure due to vibratory fatigue. This is caused by the way electric motors are powered. Pulse Width Modulation (PWM) is the control strategy of the traction chain. This signal is composed by a fundamental and numerous harmonics of voltage and current that induce harmonics onthe torquesignal resultingin hugetorque oscillations. It canlead to repeated torsionalresonance when coincidences occur. This can induce severe damages and even lead to rupture if electric excitations are not taken into account at the design stage. In this work, a magnetic finite element model is built by using Fourier decomposition in order to take into account harmonics due to PWM. Pressures exported from this model are used as inputs for mechanical FEM. A mechanical reduced order model is also proposed in order to compute stress in rotating part. This second model allows to reduce time computation and then to consider several operating points to build a complete speed up. A correlation is performed between these two models and rotating tests in order to discuss the relevance of these approaches to design rotor parts

Terahertz oscillations in ultra-thin n-In0.53Ga0.47As ungated channels

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Etude microscopique des oscillations THz dans des systèmes en InGaAs

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Etude microscopique des oscillations THz dans des systèmes en InGaAs

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Monte Carlo analysis of noise spectra in InAs channels from diffusive to ballistic regime

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Room temperature THz detection and emission with semiconductor nanodevices

In this paper we present the advances on the fabrication of THz emitters and detectors obtained within the framework of the European ROOTHz project. Two types of devices are explored, self-switching diodes and slot-diodes, using both narrow bandgap and wide bandgap semiconductors. This broad approach allows us to improve the frequency and power generated by Gunn diodes and the responsivity and noise of detectors at THz frequencies