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Smida B.B.,Preparatory Engineering Institute of Nabeul IPEIN | Majed R.,Preparatory Engineering Institute of Nabeul IPEIN | N Bouhaddi N.,FEMTO ST Institute | Ouisse M.,FEMTO ST Institute
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science | Year: 2012

In this paper, a methodology for coupled fluid-structure model reduction is proposed. The overall objective of the method is to reduce the numerical computational costs without affecting the accuracy level of the prediction. This methodology is organized according to the three following steps. In the first step, this method uses a reliable criterion for selecting the number of the kept modes for the fluid and the structure in vacuo subsystems. In the second step, this basis will be enriched through static residual responses taking into account the fluid-structure coupling effects. These responses are selected according to an energetic criterion. Finally, the enriched basis is extended by introducing some residual static responses due to the error forces considered as structural modifications forces. In the context of the finite element method (FEM), the performances of the proposed method are established through a comparative study with other strategies that are proposed in the literature. Thus, the computational cost (CPU time) and the accuracies of the different methods are discussed and compared with a reference method. The validation of the proposed method and the comparative study are performed through two numerical simulation examples. The first one concerns a parallelepiped acoustic cavity with a simply supported plate. The method can handle both weak and strong couplings; as illustrated in the examples. The second one consists of a pipe with a strong coupling and a larger model size. © 2011 Authors.


Guedri M.,Preparatory Engineering Institute of Nabeul IPEIN | Lima A.M.G.,Federal University of Itajubá | Bouhaddi N.,University of Franche Comte | Rade D.A.,Federal University of Uberlandia
Mechanical Systems and Signal Processing | Year: 2010

In this paper, a methodology of uncertainty propagation is investigated as related to constrained viscoelastic layers in the context of passive vibration damping. The uncertainties are introduced on multilayer beam and plate finite elements by means of an original strategy, which consists in introducing the perturbations after an adequate parameterisation of the mass and complex stiffness matrices. Such parameterisation scheme enables to perform iterative model updating, sensitivity analyses and uncertainty propagation analyses at a moderate computational cost since re-actualisation of the nominal global finite element matrices is not required. The design space is composed by both the parameters characterising the viscoelastic treatment and those of the base structure. The theoretical foundations related to the modelling of viscoelastic systems and stochastic finite element models are first reviewed, followed by a description of the parameterisation technique. Finally, numerical applications are presented to demonstrate the effectiveness of the proposed strategy for the robust design of structures incorporating viscoelastic materials. Crown Copyright © 2009.


Mrabet E.,Preparatory Engineering Institute of Nabeul IPEIN | Soula M.,University of Tunis | Guedri M.,Preparatory Engineering Institute of Nabeul IPEIN | Ghanmi S.,Preparatory Engineering Institute of Nabeul IPEIN | Ichchou M.,École Centrale Lyon
Lecture Notes in Mechanical Engineering | Year: 2015

The present work is intended to introduce a new reliability based optimization strategy (RBO) of single-tuned mass damper (TMD) parameters. The strategy uses an energetic approach and consists to obtain the optimum TMD parameters so that a failure probability is minimized. The failure probability is related to the dissipated power process in the primary structure (DPP) and it's characterized by the out-crossing, for the first time, of the DPP across a certain threshold value during a time interval. The introduced RBO strategy is then compared with another related to the mean value of the DPP. The obtained results show a strong correlation between the presented strategies and equivalence can be made. The effectiveness of the TMD with the proposed optimum parameters is also investigated and compared with Bituned mass dampers (Bi-TMDs). The results showed that the TMD optimized using the proposed strategy is more effective than the Bi-TMDs. © Springer International Publishing Switzerland 2015.


Abed I.,University of Franche Comte | Abed I.,Tunis el Manar University | Kacem N.,University of Franche Comte | Bouhaddi N.,University of Franche Comte | And 2 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2016

We investigate the nonlinear dynamics of magnetically coupled beams for multi-modal vibration energy harvesting. A multi-physics model for the proposed device is developed taking into account geometric and magnetic nonlinearities. The coupled nonlinear equations of motion are solved using the Galerkin discretization coupled with the harmonic balance method and the asymptotic numerical method. Several numerical simulations have been performed showing that the expected performances of the proposed vibration energy harvester are significantly promising with up to 130 % in term of bandwidth and up to 60 μWcm-3g-2 in term of normalized harvested power. © 2016 SPIE.


Rabhi N.,Preparatory Engineering Institute of Nabeul IPEIN | Guedri M.,Preparatory Engineering Institute of Nabeul IPEIN | Hassis H.,National Engineering School of Tunis | Bouhaddi N.,University of Franche Comte
Mechanical Systems and Signal Processing | Year: 2011

Mathematical modeling of physical systems is essential to understand and, if possible, control such systems. However, insufficient information may be available about the level of uncertainty related to material properties, geometric parameters, boundary conditions and the applied loads. In the context of structural reliability, the uncertainties may be uncontrollable when designing for robustness. These problems in the modeling of the uncertainties are often complicated by the models inability to describe the physical phenomena that are involved. In this paper, the proposed approach combines a dynamic reliability method and a meta-model (reduced model) to obtain good results in terms of the reliability and optimization of such systems. Using the available information about the uncertain design parameters, we use the hybrid model coupling of the possibility and probability approaches for the propagation of the uncertainties in the model. The proposed method was implemented on theoretical structures with different meta-models. The results are compared with the Monte Carlo simulations. This allowed us to prove the robustness and efficiency of the proposed methodology for reliability calculations of complex dynamic structures. © 2010 Elsevier Ltd. All rights reserved.


Abed I.,University of Franche Comte | Abed I.,Tunis el Manar University | Kacem N.,University of Franche Comte | Bouhaddi N.,University of Franche Comte | And 2 more authors.
Smart Materials and Structures | Year: 2016

We 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 4.6-4.5 Hz, with a bandwidth of 190% and a normalized power of 20.2 mW cm-3 g-2. © 2016 IOP Publishing Ltd.


Ghanmi S.,Preparatory Engineering Institute of Nabeul IPEIN | Guedri M.,Preparatory Engineering Institute of Nabeul IPEIN | Bouazizi M.-L.,Preparatory Engineering Institute of Nabeul IPEIN | Bouhaddi N.,University of Franche Comte
Mechanical Systems and Signal Processing | Year: 2011

This paper presents a new approach to robust multi-objective and multi-level optimization of the design of complex mechanical structures. The optimization is at two levels: system and elements. At system-level, the robust multi-objective problem has four cost functions: on the one hand the minimization of the global mass and displacement at a fixed point of the mechanical structure, and on the other hand the maximization of both the robustness and the displacement of the mass. At element-level the robust multi-objective problem has two cost functions: minimization of the element mass and maximization of its robustness. A robust condensation technique, based on an enriched KarhunenLoève condensation, is used for complex structures which require a large finite element model. In contrast to existing formulations, this new approach takes into account uncertainties in the design parameters at system-level and element-level. It also allows for the task sharing which is commonly used in structural engineering. © 2010 Elsevier Ltd. All rights reserved.


Abed I.,University of Franche Comte | Abed I.,Preparatory Engineering Institute of Nabeul IPEIN | Abed I.,Tunis el Manar University | Kacem N.,University of Franche Comte | And 4 more authors.
Conference Proceedings of the Society for Experimental Mechanics Series | Year: 2015

The nonlinear dynamics of a two-degree-of-freedom (2-DOFs) vibrating energy harvester (VEH) based on magnetic levitation is modeled and investigated. The equations of motion have been derived while taking into account the magnetic nonlinearity and the electro-magnetic damping. The associated linear eigenvalue problem has been analyzed and optimality conditions have been expressed in term of distance minimization between the two eigenfrequencies of the considered system. The resulting optimal design parameters have been substituted into the coupled nonlinear equations of motion which have been numerically solved. It is shown that the performances of a classical single degree of freedom VEH can be significantly enhanced up to 270% in term of power density, up to 34% in term of frequency bandwidth and up to 10% in term of resonance frequency attenuation. © The Society for Experimental Mechanics, Inc. 2015.


Guedri M.,Preparatory Engineering Institute of Nabeul IPEIN | Cogan S.,University of Franche Comte | Bouhaddi N.,University of Franche Comte
Mechanical Systems and Signal Processing | Year: 2012

Methods for the robust design of mechanical systems have the objective to reduce the variability in system performance with respect to uncertainties in the material and geometrical properties of a mechanical structure as well as in its interactions with its environment. Two types of uncertainty are encountered in practice, namely aleatory and epistemic uncertainties. Aleatory uncertainty is generally considered to be irreducible and results from statistical variations in the physical properties of components and interfaces. Epistemic uncertainties are due to a lack of accurate knowledge concerning the physical laws governing the behavior of a component or interface and can generally be reduced with a combination of more detailed modeling and experimental investigations. Epistemic uncertainties can be difficult to characterize due to simplifications in geometric and material field properties, and as such are rarely taken into account explicitly in reliability analysis. In the present work, we propose to examine the robustness of a classical reliability analysis with respect to both aleatory and epistemic uncertainty. The latter will be represented using a non-parametric approach in order to avoid a detailed characterization of the lack of knowledge present in the system. This then allows us to study in detail how the results of the reliability analysis vary as a function of the degree of lack of knowledge. The proposed methodology is illustrated using numerical simulations. © 2011 Elsevier Ltd. All rights reserved.


Mrabet E.,Preparatory Engineering Institute of Nabeul IPEIN | Guedri M.,Preparatory Engineering Institute of Nabeul IPEIN | Ichchou M.N.,École Centrale Lyon | Ghanmi S.,Preparatory Engineering Institute of Nabeul IPEIN
Mechanical Systems and Signal Processing | Year: 2015

The purpose of the current work is to present and discuss a technique for optimizing the parameters of a vibration absorber in the presence of uncertain bounded structural parameters. The technique used in the optimization is an interval extension based on a Taylor expansion of the objective function. The technique permits the transformation of the problem, initially non-deterministic, into two independents deterministic sub-problems. Two optimization strategies are considered: the Stochastic Structural Optimization (SSO) and the Reliability Based Optimization (RBO). It has been demonstrated through two different structures that the technique is valid for the SSO problem, even for high levels of uncertainties and it is less suitable for the RBO problem, especially when considering high levels of uncertainties. © 2015 Elsevier Ltd. All rights reserved.

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