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1
Content available Evaluation of the Effect of Uncertainties on the Acoustic Behavior of a Porous Material Located in a Duct Element Using the Monte Carlo Method
Hannachi Hanen, Trabelsi Hassen, Kani Marwa, Taktak Mohamed, Chaabane Mabrouk, Haddar Mohamed
Archives of Acoustics
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2023
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Vol. 48, No. 1
81--91
EN
When studying porous materials, most acoustical and geometrical parameters can be affected by the presence of uncertainties, which can reduce the robustness of models and techniques using these parameters. Hence, there is a need to evaluate the effect of these uncertainties in the case of modeling acoustic problems. Among these evaluation methods, the Monte Carlo simulation is considered a benchmark for studying the propagation of uncertainties in theoretical models. In the present study, this method is applied to a theoretical model predicting the acoustic behavior of a porous material located in a duct element to evaluate the impact of each input error on the computation of the acoustic proprieties such as the reflection and transmission coefficients as well as the acoustic power attenuation and the transmission loss of the studied element. Two analyses are conducted; the first one leads to the evaluation of the impacts of error propagation of each acoustic parameter (resistivity, porosity, tortuosity, and viscous and thermal length) through the model using a Monte Carlo simulation. The second analysis presents the effect of propagating the uncertainties of all parameters together. After the simulation of the uncertainties, the 95% confidence intervals and the maximum and minimum errors of each parameter are computed. The obtained results showed that the resistivity and length of the porous material have a great influence on the acoustic outputs of the studied model (transmission and reflection coefficients, transmission loss, and acoustic power attenuation). At the same time, the other physical parameters have a small impact. In addition, the acoustic power attenuation is the acoustic quantity least impacted by the input uncertainties.
2
Content available Robustness study of the road profile estimation technique under uncertainty
Ben Jdidia Anoire, Ben Hassen Dorra, Hentati Taissir, Abbes Slim, Haddar Mohamed
Journal of Theoretical and Applied Mechanics
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2022
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Vol. 60 nr 3
521--533
EN
This paper studies profile estimation a road. The prediction has been achieved using the Independent Component Analysis Method (ICA). The vehicle dynamic responses were cal- culated for different road profiles which were defined using an ISO norm. The robustness of this method was proven by implementing the stochastic Monte Carlo (MC) technique in the presence of inevitable uncertainty parameters simultaneously associated with the vehicle mass, spring stiffness and damping for different vehicle speeds and wind values. Convergence was assessed when comparing real profiles to simulated ones. The obtained results prove the efficiency of the ICA in estimating the profile variabilities under uncertainties.
3
Content available Evaluation of the Acoustic Performance of Porous Materials Lined Ducts with Geometric Discontinuities
Tounsi Dhouha, Taktak Wafa, Dhief Raja, Taktak Mohamed, Chaabane Mabrouk, Haddar Mohamed
Archives of Acoustics
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2022
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Vol. 47, No. 2
223--240
EN
Duct silencers provide effective noise reduction for heating, ventilation and air conditioning systems. These silencers can achieve an excellent sound attenuation through the attributes of their design. The reactive silencer works on the principle of high reflection of sound waves at low frequencies. On the other hand, the dissipative silencer works on the principle of sound absorption, which is very effective at high-frequencies. Combining these two kinds of silencers allowed covering the whole frequency range. In this paper, the effect of liner characteristics composed of a perforated plate backed by a porous material and geometry discontinuities on the acoustic power attenuation of lined ducts is evaluated. This objective is achieved by using a numerical model to compute the multimodal scattering matrix, thus allowing deducing the acoustic power attenuation. The numerical results are obtained for six configurations, including cases of narrowing and widening of a radius duct with sudden or progressive discontinuities. Numerical acoustic power attenuation shows the relative influence of the variation in the values of each parameter of the liner, and of each type of radius discontinuities of ducts.
4
Content available Identification of Physical Parameters of a Porous Material Located in a Duct by Inverse Methods
Kani Marwa, Makni Amine, Taktak Mohamed, Chaabane Mabrouk, Haddar Mohamed
Archives of Acoustics
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2021
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Vol. 46, No. 4
657--665
EN
Lined ducts with porous materials are found in many industrial applications. To understand and simulate the acoustic behaviour of these kinds of materials, their intrinsic physical parameters must be identified. Recent studies have shown the reliability of the inverse approach for the determination of these parameters. Therefore, in the present paper, two inverse techniques are proposed: the first is the multilevel identification method based on the simplex optimisation algorithm and the second one is based on the genetic algorithm. These methods are used of the physical parameters of a simulated case of a porous material located in a duct by the computation of its acoustic transfer, scattering, and power attenuation. The results obtained by these methods are compared and discussed to choose the more efficient one.
5
Content available Selection of viscous damping coefficients using the continuous wavelet transform method for a gear system
Yousfi Nourhaine, Zghal Bacem, Akrout Ali, Walha Lassaad, Haddar Mohamed
Journal of Theoretical and Applied Mechanics
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2020
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Vol. 58 nr 3
585--598
EN
Viscous damping is frequently used in the equation of motion to present the dissipation mechanism of a mechanical system. The orders of frequencies can be easily selected to determine viscous damping coefficients (VDCs) when the degree of freedom of the structure is low. For complex structures, difficulties in selecting the orders of reference frequencies to obtain reasonable VSCs are encountered. This paper mainly discusses the capability of the CWT method to select optimum frequencies of viscous damping formulation. The proposed procedure considers both the classical Rayleigh, modal and the proposed full model modal damping. The method is validated using a numerical time domain response of a two-stage gear system.
6
Content available MIMO intelligent-PID controller design for half car system based on model free control technique
Djemal Fathi, Haddar Maroua, Baslamisli S. Caglar, Chaari Riadh, Chaari Fakher, Haddar Mohamed
Journal of Theoretical and Applied Mechanics
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2020
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Vol. 58 nr 4
953--969
EN
A novel decoupled Multi-Input-Multi-Output Model Free Control strategy is presented in this paper to improve the performance of an active suspension system implemented on a half car model. To damp vibrations generated by road excitation, an algebraic online compensator was integrated in the structure of a classical PID controller to avoid the impact of unpredictable disturbances. The key element of the proposed technique is a non-asymptotic observer that can avoid the use of statistical conventional techniques. Furthermore, the advantage of easy implementation is achieved where only two accelerometers are sufficient and adequate. A comparison with classical PID and LQR is provided to demonstrate the improvement made by the proposed scheme.
7
Content available Investigation on the Effects of Acoustic Liner Variation and Geometry Discontinuities on the Acoustic Performance of Lined Ducts
Dhief Raja, Makni Amine, Taktak Mohamed, Chaabane Mabrouk, Haddar Mohamed
Archives of Acoustics
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2020
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Vol. 45, No. 1
49--66
EN
Noise reduction inside waveguide systems has gained momentum owing to a great interest in it. To attenuate the sound in a broad frequency range, this study aims to compare the effects of two acoustic liners, a perforated plate backed by an air cavity (PP-Air cavity), or by a porous material (PP-PM), on the acoustic behaviour of lined ducts using a numerical model to compute the multimodal scattering matrix. From this matrix, the reflection and the transmission coefficients are computed and therefore the acoustic power attenuation is deduced. Moreover, the effects of geometry of ducts with and without changes in the section are investigated. The numerical results are obtained for five configurations, including cases of narrowing and widening of a duct portion with sudden or progressive discontinuities. Accordingly, numerical coefficients of reflection and transmission as well as the acoustic power attenuation show the relative influence of acoustic liners in each type of configuration.
8
Content available The effect of a cracked tooth on the dynamic response of a simple gearbox with a flexible coupling under acyclism operation
Hammami Ahmed, Hmida Atef, Chaari Fakher, Khabou Mohamed Taoufik, Haddar Mohamed
Journal of Theoretical and Applied Mechanics
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2019
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Vol. 57 nr 3
591--603
EN
In this paper, the effect of a cracked tooth on the dynamic response of a simple gearbox with a flexible coupling is studied. The gearbox is driven by a combustion engine through a flexible coupling for which Nelson and Crandall’s model is used. The acyclism regime is generated by diesel engine inducing fluctuations of speed, torque and meshing stiffness. In addition, the cracked tooth of the wheel gear is modelled by lowering the meshing stiffness. After solving the equations of motion by using the Newmark method, the time response, spectrum, joint time-frequency analysis and envelope spectrum are used to characterize the dynamic response of the defected gearbox where the cracked tooth frequency is irregular and independent of the acyclism frequency.
9
Content available Road profile identification using estimation techniques: comparison between independent component analysis and Kalman filter
Chaabane Mariem Miladi, Ben Hassen Dorra, Abbes Mohamed Slim, Baslamisli Selahattin Caglar, Chaari Fakher, Haddar Mohamed
Journal of Theoretical and Applied Mechanics
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2019
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Vol. 57 nr 2
397--409
EN
This paper focuses on the identification of a road profile disturbance acting on vehicles. Vehicles are subjected to many kinds of excitation sources such as road profile irregularities, which constitute a major area of interest when designing suspension systems. Indeed, determining the road profile is important for passive suspension design on the one hand and for determining an appropriate control law for active suspensions on the other. Direct measurement techniques of the road profile are expensive, so solutions based on estimation theory are needed. The aim of this paper is to characterize the road excitation using the Independent Component Analysis (ICA). This proposed method can reconstruct original excitation sources by using physically measurable signals of the system under study. Here, the estimation of road disturbances is considered as output sources and identified from dynamic responses of the vehicle. These responses can be measured via sensors or can be numerically computed. In our case, they are numerically simulated using the Newmark method and consider different types of road profiles. The obtained results are validated after using a comparison with the Kalman filtering. The robustness of the ICA is confirmed via parametric study.
10
Content available Numerical modeling of uncertainty in acoustic propagation via generalized Polynomial Chaos
Dammak Khalil, Koubaa Sana, Elhami Abdelkhalak, Walha Lassaad, Haddar Mohamed
Journal of Theoretical and Applied Mechanics
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2019
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Vol. 57 nr 1
3--15
EN
This work aims at increasing the performance prediction for acoustic propagation systems that will operate in the presence of the inevitable parameters uncertainty. In the present contribution, the finite element method is applied to solve an acoustic problem described by the Helmholz equation when the geometric and material properties present uncertainty. The influence of the uncertainty of physical parameters on the pressure field is discussed. The results using the polynomial chaos expansion method are compared with Monte Carlo simulations. It is show that uncertainty levels in the input data could result in large variability in the calculated pressure field in the domain.
11
Content available Numerical and experimental analysis of a segmented wind turbine blade under assembling load effects
Yangui Majdi, Bouaziz Slim, Taktak Mohamed, Debut Vincent, Antunes Jose, Haddar Mohamed
Journal of Theoretical and Applied Mechanics
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2019
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Vol. 57 nr 1
85--97
EN
In this paper, numerical and experimental modal analysis of a segmented wind turbine blade assembled with a steel threaded shaft and a nut are presented. The blade segments are built by a 3D printer using ABS material. The experimental modal parameters identification has been achieved using the Eigen system Realization Algorithm (ERA) method for different values of the blade segments assembly force caused by the nut tightening torque. Furthermore, a three dimensional finite element model has been built using DTK18 three node triangular shell elements in order to model the blade and the threaded shaft structure, taking into account the additional stiffness caused by the nut tightening torque. This study covers the blade segments assembly force effects on the rotating blade vibration characteristics. The numerical model is adjusted and validated by the identified experimental results. This work highlights the significant variation of the natural frequencies of the segmented wind turbine blade by the assembling load of the segments versus blade rotating speed.
12
Content available Consideration of uncertainties in the preliminary design case of an electromagnetic spindle
Trabelsi Hassen, Guizani Amir, Tounsi Dhouha, Hammadi Moncef, Barkallah Maher, Haddar Mohamed
Journal of Theoretical and Applied Mechanics
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2019
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Vol. 57 nr 4
821--832
EN
Modeling and evaluation of uncertainties constitute indeed one of the key points when making any decision. For this, designers have to compare the measured or calculated value with a range of permissible values in order to obtain a guaranteed design process. Thus, in this work, simulation of the dynamic behavior of an electromagnetic spindle was done based on the interval computation technique. Indeed, the use of this technique makes it possible to obtain a set of values for different design parameters of the spindle and, consequently, to avoid making several simulations which could make the system useless, expensive or ineffective. The proposed model is based on the combination of Matlab with ModelCenter. Matlab was used to model and simulate the system and ModelCenter to perform parametric studies to verify the influences of uncertainty on the dynamic behavior of the electromagnetic spindle and to determine the optimal design parameters.
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