Laboratoire Of Genie Mecanique

Hammam Sousse, Tunisia

Laboratoire Of Genie Mecanique

Hammam Sousse, Tunisia
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Bouzouita S.,CNRS Tribology and Dynamic Systems Laboratory | Salvia M.,CNRS Tribology and Dynamic Systems Laboratory | Ben Daly H.,Laboratoire Of Genie Mecanique | Dogui A.,Laboratoire Of Genie Mecanique
Proceedings of the 6th European Workshop - Structural Health Monitoring 2012, EWSHM 2012 | Year: 2012

In recent years high interests of scientific and industrial worlds were concentrated on natural fibers composites. Natural fibers as hemp, flax and sisal have become suitable alternatives to glass fibers as NFs present several advantages as lightness, strength, recyclability and are relatively cheap and abundant. However, their high hygroscopic nature and their sensitivity to temperature must be taken into account. In this paper, the influence of hygrothermal aging on mechanical behaviour of Hemp/ isotactic polypropylene composites were studied using flexural tests associated to acoustic emission (AE).


Benkedjouh T.,Laboratoire Of Mecanique Des Structures Lms | Medjaher K.,FEMTO ST Institute | Zerhouni N.,FEMTO ST Institute | Rechak S.,Laboratoire Of Genie Mecanique
Engineering Applications of Artificial Intelligence | Year: 2013

Prognostics and health management (PHM) of rotating machines is gaining importance in industry and allows increasing reliability and decreasing machines' breakdowns. Bearings are one of the most components present in mechanical equipments and one of their most common failures. So, to assess machines' degradations, fault prognostic of bearings is developed in this paper. The proposed method relies on two steps (an offline step and an online step) to track the health state and predict the remaining useful life (RUL) of the bearings. The offline step is used to learn the degradation models of the bearings whereas the online step uses these models to assess the current health state of the bearings and predict their RUL. During the offline step, vibration signals acquired on the bearings are processed to extract features, which are then exploited to learn models that represent the evolution of the degradations. For this purpose, the isometric feature mapping reduction technique (ISOMAP) and support vector regression (SVR) are used. The method is applied on a laboratory experimental degradations related to bearings. The obtained results show that the method can effectively model the evolution of the degradations and predict the RUL of the bearings. © 2013 Elsevier Ltd.


Laribi M.A.,Laboratoire Of Genie Mecanique | Laribi M.A.,University of Poitiers | Romdhane L.,Laboratoire Of Genie Mecanique | Zeghloul S.,University of Poitiers
Journal of Zhejiang University: Science A | Year: 2011

In this work, a systematic approach is presented to obtain the input-output equations of a single loop 4-bar spatial mechanisms. The dialytic method along with Denavit-Hartenberg parameters can be used to obtain these equations efficiently. A genetic algorithm (GA) has been used to solve the problem of spatial mechanisms synthesis. Two types of mechanisms, e.g.; RSCR and RSPC (R: revolute; S: spherical; C: cylindrical; P: prismatic), have illustrated the application of the GA to solve the problem of function generation and path generation. In some cases, the GA method becomes trapped in a local minimum. A combined GA-fuzzy logic (GA-FL) method is then used to improve the final result. The results show that GAs, combined with an adequate description of the mechanism, are well suited for spatial mechanism synthesis problems and have neither difficulties inherent to the choice of the initial feasible guess, nor a problem of convergence, as it is the case for deterministic methods. © 2011 Zhejiang University and Springer-Verlag Berlin Heidelberg.


Bouzouita S.,École Centrale Lyon | Bouzouita S.,Laboratoire Of Genie Mecanique | Salvia M.,École Centrale Lyon | Daly H.B.,Laboratoire Of Genie Mecanique | And 2 more authors.
Advanced Materials Research | Year: 2010

The use of natural fibers as reinforcement in composites is emerging. Several studies are underway to improve the mechanical characteristics of these fibers and its matrix interface properties for better load transfer. However, the treatments generally used are relatively expensive and complicated to apply. This work deals with the effect of new Fibroline process on tensile and interfacial properties of hemp fiber reinforced in polypropylene. Fibroline is a dry powder impregnation method which consists of submitting fibers and polymer powder under strong alternating electric field. Morphology and tensile properties of hemp fibers after different surface treatments (raw, dried, raw and Fibroline-treated, dried and Fibroline-treated) are evaluated. Interface properties of treated hemp fibers on polypropylene matrix are then characterized by fragmentation test of monofilament composites. Results showed the Fibroline treatment reduces the fiber mechanical properties but improves the load transfer efficiency due to random generation of surface cracks and better fiber/matrix adherence, respectively. For the case of dried and Fibroline- treated hemp fibers, large decrease in mechanical and interfacial properties was observed. © (2010) Trans Tech Publications, Switzerland.


Baho O.,Laboratoire Of Genie Mecanique | Baho O.,École Centrale Lyon | Zergoune Z.,Laboratoire Of Genie Mecanique | Zergoune Z.,École Centrale Lyon | And 5 more authors.
Composite Structures | Year: 2016

The present paper investigates the vibroacoustics of honeycomb sandwich panels using both analytical and numerical approaches. In a typical sandwich structure, the acoustic transmission in the low and mid frequency ranges is generally controlled by global bending waves and by core shear effects. This behavior defines two frequency bands of great interest for the vibroacoustic signature. The transition frequency is then an important parameter to predict. In the present work, transition frequency expressions of honeycomb sandwich panels are derived using both a homogenized analytical method and a three-dimensional numerical approach. The expressions obtained show the panel geometry and the core properties influence. Also, they take into account the orthotropic effect of the entire panel and the transverse shear effect of the sandwich core. The accuracy of the predictions based on the two approaches has been verified by comparing the results obtained with previously published analytical models, showing a good agreement as far as the sandwich panel exhibits an isotropic behavior. However, when the orthotropic behavior of the sandwich panel becomes important, corrections are needed and provided. © 2016 Elsevier Ltd


Droz C.,École Centrale Lyon | Zergoune Z.,École Centrale Lyon | Zergoune Z.,Laboratoire Of Genie Mecanique | Boukadia R.,École Centrale Lyon | And 2 more authors.
Composite Structures | Year: 2016

This paper investigates the use of a wave-based method in the framework of structural optimisation of composite panels involving advanced components. The wave/finite element method (WFEM) is used to evaluate the influence of a core's geometry on the transition frequency of a sandwich panel involving composite skins. This transition occurs is a sandwich panel when the transverse shear stiffness has a significant influence on the flexural motion, compared to the bending stiffness. It follows that the modal density and the acoustic radiation will considerably increase above this frequency. The periodic waveguide is modelled at the mesoscopic scale using a 3D finite element model of the unit-cell. Therefore this method does not require an homogenisation of the core based on Gibson and Ashby formulations to provide the wave dispersion characteristics. Although the cellular cores compared in this study share the same mass-to-stiffness ratio, a significant alteration of the transition frequency and modal density can be observed compared to honeycomb cores. A periodic octagonal core is designed, providing up to 70% increase of the transition frequency and a significant reduction of the modal density. © 2016 Elsevier Ltd.


Chebbi A.H.,Laboratoire Of Genie Mecanique | Affi Z.,Laboratoire Of Genie Mecanique | Romdhane L.,Laboratoire Of Mecanique
Lecture Notes in Mechanical Engineering | Year: 2013

This work deals with the kinematics and singularity of the spherical 3-UPU parallel manipulator. Firstly the structure of the spherical 3-UPU robot is presented. Then the forward kinematic model is developed where the roll, pitch and yaw angles describing the orientation of the mobile platform are given in a closed form. We prove that the forward kinematic problem has eight solutions. Based on the developed model, the singularity of the manipulator is analyzed and we show that the workspace of the spherical 3-UPU manipulator is free of singularity. To illustrate this study some simulations are given for a given 3-UPU architecture. © Springer-Verlag Berlin Heidelberg 2013.


Mehdaoui A.,Laboratoire Of Genie Mecanique | Abouchita J.,Laboratoire Of Genie Mecanique
Materiaux et Techniques | Year: 2011

From aerospace to daily uses passing through the medical, the civil engineering and leisures, elastomers have shown evidence of a fundamental importance considering the large spectrum of their pertinent uses. The present work is made in the perspective to study, by the finite-element method, the answer of hyperelastic incompressible elastomeric pieces or structures subjected to large deformations. To take account of the incompressibility, the handling of the problem of the static equilibrium in nonlinear elasticity is based on the modified potential energy function. The incompressibility property makes the development of a computer code very delicate because it provokes highly numerical instabilities. To face it, a particular formulation and a three-dimensional quadratic finite-element with 20 nodes were implemented for the analysis of finite deformations of incompressible or quasi-incompressible hyperelastic materials. The validation of the developed quadratic element is made on examples with analytic solutions. Then, the validated element is exploited to the design of an industrial component constituted of a laminated rubber/metal, with an exploration of the stress state in the various elastomeric layers. © 2011 EDP Sciences.


Benkedjouh T.,Laboratoire Of Mecanique Des Structures Lms | Medjaher K.,University of Franche Comte | Zerhouni N.,University of Franche Comte | Rechak S.,Laboratoire Of Genie Mecanique
Journal of Intelligent Manufacturing | Year: 2015

The integrity of machining tools is important to maintain a high level of surface quality. The wear of the tool can lead to poor surface quality of the workpiece and even to damage of the machine. Furthermore, in some applications such as aeronautics and precision engineering, it is preferable to change the tool earlier rather than to loose the workpiece because of its high price compared to the tool’s one. Thus, to maintain a high quality of the manufactured pieces, it is necessary to assess and predict the level of wear of the cutting tool. This can be done by using condition monitoring and prognostics. The aim is then to estimate and predict the amount of wear and calculate the remaining useful life (RUL) of the cutting tool. This paper presents a method for tool condition assessment and life prediction. The method is based on nonlinear feature reduction and support vector regression. The number of original features extracted from the monitoring signals is first reduced. These features are then used to learn nonlinear regression models to estimate and predict the level of wear. The method is applied on experimental data taken from a set of cuttings and simulation results are given. These results show that the proposed method is suitable for assessing the wear evolution of the cutting tools and predicting their RUL. This information can then be used by the operators to take appropriate maintenance actions. © 2013, Springer Science+Business Media New York.


Lachheb M.,Laboratoire des Etudes des Systemes Thermiques et Energetiques LESTE | Albouchi F.,Laboratoire des Etudes des Systemes Thermiques et Energetiques LESTE | Mzali F.,Laboratoire des Etudes des Systemes Thermiques et Energetiques LESTE | Nasrallah S.B.,Laboratoire des Etudes des Systemes Thermiques et Energetiques LESTE | Benameur T.,Laboratoire Of Genie Mecanique
International Journal of Heat and Technology | Year: 2013

This paper deals with the analysis of a LiNO3/ graphite composite for thermal storage at high temperature. In such a composite, the salt (LiNO3) serves as a latent heat storage material and the graphite has been used to enhance the thermal conductivity of the salts. The elaboration method consists of a cold uni-axial compression of a physical mixing of salts powder and graphite particles. The thermal conductivity of the LiNO3/ graphite composites with different mass fraction of graphite was measured using transient hot wire technique. Also, the influence of the moisture content on the measurement was studied.

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