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Hammam Sousse, Tunisia

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

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. Source

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

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. Source

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

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. Source

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

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. Source

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

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. Source

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