Optimisation robuste multi-niveaux et multi-objectif de structures mécaniques complexes

Cet article présente une nouvelle approche d’optimisation multi-objectifs robuste, et multi-niveaux, pour la conception des structures mécaniques complexes. Cette optimisation est à deux niveaux : système et élément. Le problème multi-objectifs robuste, au niveau système, à résoudre est à quatre fonctions coût : d’une part la minimisation de la masse globale et le déplacement en un point fixé de la structure mécanique étudiée, d’autre part la maximisation des robustesses respectivement de la masse et du déplacement alors que le problème multi-objectifs robuste au niveau élément est à deux fonctions coût : la minimisation de la masse de l’élément et la maximisation de sa robustesse. Contrairement aux formulations existantes, cette nouvelle approche tient compte des incertitudes sur les paramètres de conception tant au niveau système qu’au niveau élément. De plus, elle répond au partage des tâches pratiqué dans l’industrie

Composite beam identification using a variant of the inhomogeneous wave correlation method in presence of uncertainties

International audiencePurpose: This paper aims to propose numerical-based and experiment-based identification processes, accounting for uncertainties to identify structural parameters, in a wave propagation framework.Design/methodology/approach: A variant of the inhomogeneous wave correlation (IWC) method is proposed. It consists on identifying the propagation parameters, such as the wavenumber and the wave attenuation, from the frequency response functions. The latters can be computed numerically or experimentally. The identification process is thus called numerical-based or experiment-based, respectively. The proposed variant of the IWC method is then combined with the Latin hypercube sampling method for uncertainty propagation. Stochastic processes are consequently proposed allowing more realistic identification.Findings: The proposed variant of the IWC method permits to identify accurately the propagation parameters of isotropic and composite beams, whatever the type of the identification process in which it is included: numerical-based or experiment-based. Its efficiency is proved with respect to an analytical model and the Mc Daniel method, considered as reference. The application of the stochastic identification processes shows good agreement between simulation and experiment-based results and that all identified parameters are affected by uncertainties, except damping.Originality/value: The proposed variant of the IWC method is an accurate alternative for structural identification on wide frequency ranges. Numerical-based identification process can reduce experiments’ cost without significant loss of accuracy. Statistical investigations of the randomness of identified parameters illustrate the robustness of identification against uncertainties

Multi-modal vibration energy harvesting approach based on nonlinear oscillator arrays under magnetic levitation

International audienceWe propose a multi-modal vibration energy harvesting approach based on arrays of coupled levitated magnets. The equations of motion which include the magnetic nonlinearity and the electromagnetic damping are solved using the harmonic balance method coupled with the asymptotic numerical method. A multi-objective optimization procedure is introduced and performed using a non-dominated sorting genetic algorithm for the cases of small magnet arrays in order to select the optimal solutions in term of performances by bringing the eigenmodes close to each other in terms of frequencies and amplitudes. Thanks to the nonlinear coupling and the modal interactions even for only three coupled magnets, the proposed method enable harvesting the vibration energy in the operating frequency range of 4.6–14.5 Hz, with a bandwidth of 190% and a normalized power of 20.2 mW cm-3 g-2

Structural Analysis and Theoretical Investigations of the Magnetocaloric Effect for La0.7Ba0.15Ag0.15MnO3 Manganite Prepared Using Sol-Gel Route

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Magnetocaloric effect study by means of theoretical models and spontaneous magnetization determination in Ni 0.4 Mg 0.3 Cu 0.3 Fe 2 O 4 ferrite

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Synthesis and study of impendence spectroscopy properties of La0.6Ca0.2Na0.2MnO3 manganite perovskite prepared using sol–gel method

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Study of the Magnetocaloric Effect by Means of Theoretical Models in La0.6Ca0.2Na0.2MnO3 Manganite Compound

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Parametric study on energy pumping of Mdof system using multiple dynamic absorbers

International audienceThe concept of energy pumping is an innovative dynamic phenomenon. This phenomenon gives rise to a new generation of dynamic absorbers. Theoretical studies and feasibility tests are necessary for a better understanding of their dynamic behaviour and for them to be applied on real structures or machines. In this paper, numerical evidence is firstly given for the passive and broadband targeted energy transfer in the case of a linear system (Machine for example) under shock excitation with Multiple Dynamic Absorbers (MDA). Secondly, it is shown that many MDA absorb shock energy in a one way irreversible fashion and dissipate this energy locally, without “spreading” it back to the linear system. Finally,numerical results in the case of MDA linked to a linear beam are compared to Tuned Mass Dampers (TMD absorbers) linked to the same linear beam

Critical behaviors near the paramagnetic-ferromagnetic phase transitions of La 0.47 Eu 0.2 Pb 0.33 MnO 3 and La 0.47 Y 0.2 Pb 0.33 MnO 3 perovskites

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