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1

Effects of viscoelastic and porous materials on sound transmission of multilayer systems

Felhi H., Trabelsi H., Taktak M., Chaabane M., Haddar M.

Journal of Theoretical and Applied Mechanics

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2018

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Vol. 56 nr 4

961--976

EN

Multilayer structures allow obtaining good performance in acoustic insulation to eliminate unwanted noise in the medium and high frequencies in many applications such as building and transport industry. In this paper, the sound transmission of multilayer systems is studied using the Transfer Matrix Method (TMM). The studied multi-layered panels include elastic, viscoelastic and porous materials. Several configurations of multilayer systems are studied, and their corresponding transmission loss T L is computed. Also, the effects of porous material characteristics are studied to evaluate the impact of each parameter.

2

Effect of the gear local damage and profile error of the gear on the drivetrain dynamic response

Ghorbel A., Zghal B., Abdennadher M., Walha L., Haddar M.

Journal of Theoretical and Applied Mechanics

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2018

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Vol. 56 nr 3

765--779

EN

The dynamic modeling of vibration of a drivetrain is used for increasing our information about vibration generating mechanisms, especially in the presence of some kind of gear faults. This paper describes a research work on the automotive driveline modeling, vibration analysis, and the effect of gear defects on the dynamic behavior of the system. Firstly, main drivetrain components including the engine, clutch, single stage spur gearbox and disc brake are modeled, respectively. The nonlinear dynamic model is simulated by a thirteen degrees of freedom (DOF) system and the nonlinear function is due to the dry friction path. Secondly, two types of defects are modeled and introduced into the spur gear system; local damage and profile error. Then, the nonlinear equations of motion are solved by the numerical Runge Kutta method and a comparative study of the dynamic behavior of the system in healthy and defected cases is discussed for each fault type. The influence of the defects on the vibration response is presented in the time and frequency domain. Finally, analysis of the two defects together is presented.

3

Vibration analysis of three-layered nanobeams based on nonlocal elasticity theory

Kammoun N., Jrad H., Bouaziz S., Soula M., Haddar M.

Journal of Theoretical and Applied Mechanics

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2017

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Vol. 55 nr 4

1299--1312

EN

In this paper, the first investigation on free vibration analysis of three-layered nanobeams with the shear effect incorporated in the mid-layer based on the nonlocal theory and both Euler Bernoulli and Timoshenko beams theories is presented. Hamilton’s formulation is applied to derive governing equations and edge conditions. In order to solve differential equations of motions and to determine natural frequencies of the proposed three-layered nanobeams with different boundary conditions, the generalized differential quadrature (GDQM) is used. The effect of the nanoscale parameter on the natural frequencies and deflection modes shapes of the three layered-nanobeams is discussed. It appears that the nonlocal effect is important for the natural frequencies of the nanobeams. The results can be pertinent to the design and application of MEMS and NEMS.

4

Stability analysis and dynamic behaviour of a flexible asymmetric rotor supported by active magnetic bearings

Attia Hili M., Bouaziz S., Haddar M.

Journal of Theoretical and Applied Mechanics

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2017

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Vol. 55 nr 3

751--763

EN

The objective of this work is to show the influence of dynamic characteristics of Active Magnetic Bearings (AMBs) on the stability and dynamic response of an asymmetric and unbalanced rotor. Indeed, AMBs have been successfully applied in several industrial machinery facilities. Their main advantages are the contactless working principle, frictionless suspension and operation in very high speeds. Firstly, the AMBs dynamic support parameters have been obtained through electromagnetic theory. Then, a generalized system equations of motion have been derived using the finite element method. The motion of a rotor the shaft cross-section of which is asymmetric is generally governed by ordinary differential equations with periodic coefficients. Floquet’s theory is used to investigate the stability of this system of equations. Finally, numerical simulation results are presented and discussed.

5

Porous material effect on gearbox vibration and acoustic behavior

Letaief M. R., Walha L., Taktak M., Chaari F., Haddar M.

Journal of Theoretical and Applied Mechanics

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2017

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Vol. 55 nr 4

1381--1395

EN

In this paper, we define a resolution method to study the effect of a porous material on vibro-acoustic behavior of a geared transmission. A porous plate is coupled with the gearbox housing cover. The developed model depends on the gearbox characteristic and poroelastic parameters of the porous material. To study the acoustic effect of the housing cover, the acoustic transmission loss is computed by simulating numerically the elastic-porous coupled plate model, and the numerical implementation is performed by directly programming the mixed displacement-pressure formulation. To study the vibration effect, the bearing displacement is computed using a two-stage gear system dynamical model and used as the gearbox cover excitation. Numerical implementation is performed by direct programming of the Leclaire formulation.

6

Modal analysis of gearbox transmission system in bucket wheel excavator

Karray M., Feki N., Khabou M. T., Chaari F., Haddar M.

Journal of Theoretical and Applied Mechanics

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2017

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Vol. 55 nr 1

253--264

EN

Planetary gears are widely used in modern machines as ones of the most effective forms of power transmission. In this paper, a special configuration of a gearbox composed of one stage spiral bevel gear and a two stage helical planetary gear used in a bucket wheel excavator gearbox is presented to investigate its modal properties. A lumped-parameter model is formulated to obtain equations of motion and the eigenvalue problem is solved. The modes are presented in low-frequency and high-frequency bands. Distributions of modal kinetic and strain energies are studied.

7

Effect of geometry and impedance variation on the acoustic performance of a porous material lined duct

Masmoudi A., Makni A., Taktak M., Haddar M.

Journal of Theoretical and Applied Mechanics

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2017

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Vol. 55 nr 2

679--694

EN

In this paper, the effect of geometry and impedance on the acoustic behavior of wall and lined cylindrical ducts is investigated using a numerical model which enables one to compute the reflection and the transmission coefficients of such ducts using the multimodal scattering matrix. From this matrix, the acoustic power attenuation is deduced. By using these tools, the effect of duct diameter increase and duct diameter decrease of the wall or lined duct section is studied. The numerical results are obtained for two configurations of wall and lined ducts. Numerical coefficients of transmission and reflection as well as the acoustic power attenuation show the relative influence of each type of variation.

8

Mode of failure for reinforced concrete beams with GFRP bars

Masmoudi A., Ouezdou M. B., Haddar M.

Journal of Theoretical and Applied Mechanics

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2016

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Vol. 54 nr 4

1137--1146

EN

Crack propagation in concrete structures is a very complicated process. An experimental method to predict the stress distribution of a cracked GFRP reinforced concrete flexural beam is presented. The beam subjected to four-point bending is internally reinforced with unidirectional GFRP bars. The aim of this investigation is to study the flexural performance of reinforced concrete members strengthened using GFRP bars. For the flexural tests performed on reinforced concrete beams strengthened with GFRP bars, the ultimate load of the beams strengthened with GFRP was reasonably increased. The mode of failure for beams reinforced with GFRP sections is slightly different compared with the traditional beam. The GFRP reinforced concrete beams fail either by concrete crushing at the compression zone or rupture of the GFRP reinforcement.

9

Influence of uncertainty in aerodynamic performance on the dynamic response of a two stage gear system

Tounsi M., Beyaoui M., Abboudi K., Feki N., Walha L., Haddar M.

Journal of Theoretical and Applied Mechanics

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2016

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Vol. 54 nr 2

601--612

EN

In this paper, the nonlinear dynamic response in a wind turbine system is considered and the quantification of uncertainty effects on the variability of this nonlinear response is investigated. Under dynamic conditions, a lumped model with 12 degrees of freedom is proposed taking into account the uncertainty associated to the power coefficient of the input aerodynamic torque. The dynamic response of the two-stage spur gear system is obtained using ODE45 solver of Matlab. The Polynomial Chaos (PC) method is used to introduce the uncertainties on the proposed model. A comparison between the two dynamic responses given by the proposed lumped dynamic model takes into account the uncertainty. It is performed on the existed model without uncertainty. Thus, the efficiency and robustness of the proposed new methodology is evaluated.

10

Guided wave propagation in thermal media through the semi analytical finite element method

Bouchoucha F., Chaabane S., Ichchou M. N., Haddar M.

Journal of Theoretical and Applied Mechanics

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2016

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Vol. 54 nr 1

285--293

EN

In this paper, the issue of the estimation of wave propagation characteristics in thermal media is dealt with. A formulation, named the Thermal Semi Analytical Finite Element, based on the semi analytical finite element approach coupled with the thermal effect is offered. Temperature variations affect the mechanical properties of the waveguide. The question of dispersion curves and group velocities is studied. This study is expected to be of use in the sensitivity analysis of guided waves for wave propagation in thermal environment. Comparisons between numerical and analytical results are given to show the effectiveness of the proposed approach.

11

Dynamic response of a spur gear system with uncertain parameters

Guerine A., Hami A. E., Walha L., Fakhfakh T., Haddar M.

Journal of Theoretical and Applied Mechanics

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2016

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Vol. 54 nr 3

1039--1049

EN

In this paper, we propose a new approach for taking into account uncertainties based on the projection on polynomial chaos. The new approach is used to determine the dynamic response of a spur gear system with uncertainty associated to gear system parameters. The simulation results are obtained by the polynomial chaos approach for dynamic analysis under uncertainty. The proposed approach is an efficient probabilistic tool for uncertainty propagation. It has been found to be an interesting alternative to the parametric studies. The polynomial chaos results are compared with Monte Carlo simulations.

12

Cutting parameters and vibrations analysis of magnetic bearing spindle in milling process

Bouaziz A., Barkallah M., Bouaziz S., Choley J. Y., Haddar M.

Journal of Theoretical and Applied Mechanics

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2016

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Vol. 54 nr 3

691--703

EN

In modern production, milling is considered the widespread cutting process in the formatting field. It remains important to study this manufacturing process as it can be subject to some parasitic phenomena that can degrade surface roughness of the machined part, increase tool wear and reduce spindle life span. In fact, the best quality work piece is obtained with a suitable choice of parameters and cutting conditions. In another hand, the study of tool vibrations and the cutting force attitude is related to the study of bearings as they present an essential part in the spindle system. In this work, a modeling of a High Speed Milling (HSM) spindle supported by two pair of Active Magnetic Bearings (AMB) is presented. The spindle is modeled by Timoshenko beam finite elements where six degrees of freedom are taken into account. The rigid displacements are also introduced in the modeling. Gyroscopic and centrifugal terms are included in the general equation. The bearings reaction forces are modeled as linear functions of journal displacement and velocity in the bearing clearance. A cutting force model for peripheral milling is proposed to estimate the tool-tip dynamic responses as well as dynamic cutting forces which are also numerically investigated. The time history of response, orbit, FFT diagram at the tool-tip center and the bearings dynamic coefficients are plotted to analyze dynamic behavior of the spindle.

13

Pre-designing of a mechatronic system using an analytical approach with Dymola

Hamza G., Choley J.-Y., Hammadi M., Riviere A., Barkallah M., Louati J., Haddar M.

Journal of Theoretical and Applied Mechanics

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2015

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Vol. 53 nr 3

697--710

EN

This paper presents a pre-dimensioning method applied to a mechatronic system and regarding the vibrational aspect, through a simple modeling process in Dymola environment. We study the vibration transmission between dynamic exciters (motors) and receivers (electronic cards) which are located on a simply supported rectangular plate, using an analytical approach. This new method will allow us to perform representative and robust modeling and simulation. The solution for this issue would be a pre-sizing and pre-positioning procedure. It aims to determine a set of possible technical solutions and principal characteristics before the definitive choice of components and precise sizing of the system. The presented method predicts also behaviour of the mechatronic system. In order to validate the model with respect to the finite element method, selected simulation results are presented.

14

Modal analysis of back-to-back planetary gear: experiments and correlation against lumped-parameter model

Hammami A., Rincon A. F. del, Rueda F. V., Chaari F., Haddar M.

Journal of Theoretical and Applied Mechanics

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2015

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Vol. 53 nr 1

125--138

EN

In order to characterize the dynamic behaviour of a back-to-back planetary gear, experimental and numerical modal analysis techniques are achieved. Rotational and translational modal deflections are highlighted. Natural frequencies are compared to the results from the lumped-parameter model. The modes are presented in the numerical studies in low-frequency and high-frequency bands. Distributions of modal kinetic and strain energies are studied.

15

Inverse method for a one-stage spur gear diagnosis

Akrout A., Tounsi D., Taktak M., Abbes M. S., Haddar M.

Journal of Theoretical and Applied Mechanics

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2015

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Vol. 53 nr 3

617--628

EN

In this paper, a source separation approach based on the Blind Source Separation (BSS) is presented. In fact, the Independent Component Analysis (ICA), which is the main technique of BSS, consists in extracting different source signals from several observed mixtures. This inverse method is very useful in many fields such as telecommunication, signal processing and biomedicine. It is also very attractive for diagnosis of mechanical systems such as rotating machines. Generally, dynamic responses of a given mechanical system (displacements, accelerations and speeds) measured through sensors are used as inputs for the identification of internal defaults. In this study, the ICA concept is applied to the diagnosis of a one-stage gear mechanism in which two types of defects (the eccentricity error and the localized tooth defect)are introduced. The finite element method allows determination of the signals corresponding to the acceleration in some locations of the system, and those signals may be used also in the ICA algorithm. Hence, the vibratory signatures of each defect can be identified by the ICA concept. Thus, a good agreement is obtained by comparing the expected default signatures to those achieved by the developed inverse method.

16

Effect of Liner Characteristics on the Acoustic Performance of Duct Systems

Othmani C., Hentati T., Taktak M., Elnady T., Fakhfakh T., Haddar M.

Archives of Acoustics

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2015

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Vol. 40, No. 1

117--127

EN

Porous materials are used in many vibro-acoustic applications. Different models describe their performance according to material’s intrinsic characteristics. In this paper, an evaluation of the effect of the porous and geometrical parameters of a liner on the acoustic power attenuation of an axisymmetric lined duct was performed using multimodal scattering matrix. The studied liner is composed by a porous material covered by a perforated plate. Empirical and phenomenal models are used to calculate the acoustic impedance of the studied liner. The later is used as an input to evaluate the duct attenuation. By varying the values of each parameter, its influence is observed, discussed and deduced.

17

Vibro-acoustic analysis of laminated double glazing using the force identification method

Ben Jdidia M, Akrout A, Tounsi D, Fakhfakh T., Haddar M.

Journal of Theoretical and Applied Mechanics

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2014

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Vol. 52 nr 4

895--904

EN

This paper presents a procedure for identifying wave forms and excitation frequencies of some forces applied on a given complex fluid-structure coupled system by using only its vibro-acoustic response. The considered concept is called the Independent Component Analysis (ICA) which is based on the Blind Source Separation (BSS). In this work, the ICA method is exploited in order to determine the excitation force applied to a thin-film laminated double glazing system enclosing a thin fluid cavity and limited by an elastic joint. The dynamic response of the studied fluid-structure coupled system is determined by finite element discretization and minimization of the homogenized energy functional of the coupled problem. This response will serve as the input for the ICA algorithm in order to extract the applied excitation.

18

Numerical characterization of an axisymmetric lined duct with flow using the multimodal scattering matrix

Taktak M., Majdoub M. A., Haddar M., Bentahar M.

Journal of Theoretical and Applied Mechanics

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2013

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Vol. 51 nr 2

313--325

EN

In this paper, the development of a numerical method to compute the multimodal scattering matrix of a lined duct in the presence of flow is presented. This method is based on the use of the convected Helmholtz equation and the addition of modal pressures at duct boundaries as additional degrees of freedom of the system. The boundary effects at the inlet and outlet of the finite waveguide are neglected. The choice of this matrix is justified by the fact that it represents an intrinsic characterization of a duct system. The validation of the proposed finite element is done by a comparison with the analytical formulation for simple cases of ducts. Then, the numerical coefficients of the scattering matrix of a lined duct and its acoustic power attenuation are computed for several flow velocities to evaluate the flow effect.

PL

W pracy zaprezentowano numeryczną metodę wyznaczania macierzy rozpraszania dla wyściełanego przewodu z uwzględnieniem wewnętrznego przepływu czynnika. Metodę oparto na zastosowaniu równania konwekcji Helmholtza z wprowadzeniem ciśnień modalnych na brzegach jako dodatkowych stopni swobody układu. Efekty brzegowe na wlocie i wylocie przewodu falowego o skończonej długości pominięto. Wybór macierzy rozpraszania uzasadniono faktem, że reprezentuje ona wewnętrzną charakterystykę analizowanego modelu. Zaproponowany element skończony zweryfikowano poprzez porównanie z istniejącymi rozwiązaniami analitycznymi dla prostych przypadków konfiguracji przewodu. Następnie numerycznie obliczono wartości elementów macierzy rozpraszania oraz współczynniki tłumienia akustycznego dla kilku prędkości przepływu w celu określenia, jak dalece wpływa on na badany układ.

19

Numerical Modelling of the Acoustic Pressure Inside an Axisymmetric Lined Flow Duct

Taktak M., Majdoub M. A., Bentahar M., Haddar M.

Archives of Acoustics

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2012

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Vol. 37, No. 2

151-160

EN

Numerical methods are mostly used to predict the acoustic pressure inside duct systems. In this paper, the development of a numerical method based on the convected Helmholtz equation to compute the acoustic pressure inside an axisymmetric duct is presented. A validation of the proposed method was done by a comparison with the analytical formulation for simple cases of hard wall and lined ducts. The effect of the flow on the acoustic pressure inside these ducts was then evaluated by computing this field with different Mach numbers.

20

Processing Transient Response of a Flexible Rotor-Bearing System with Unbalanced Disk

Attia Hili M., Bouaziz S., Maatar M., Fakhfakh T., Haddar M.

Machine Dynamics Research

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2010

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Vol. 34, No. 1

23-37

EN

Turbomachinery rotors are frequently supported on several oil lubricating bearings and so are statically indeterminate. In such cases, the bearings reaction forces and hence their stiffness and damping properties affect the relative location of the bearing centres, thereby significantly the vibration behaviour of the rotor bearing system. In this paper, the dynamic behaviour of symmetrical rotor bearing system with unbalanced disk is analyzed based on a continuum model. The finite difference method is employed with the successive over relaxation technique to solve the Reynolds equation. The finite element method with an iteration scheme is adopted in the analysis of the system state trajectories. Bearing's stiffness and damping are considered. The motions of journal and disk have been simulated with Newmark method. Linear transient simulation, with time integration procedure, and unbalanced responses are investigated. The present results provide a deeper understanding to predict undesirable behaviour of the rotor and bearings centres can be avoided.