Browsing by Author "Meloussi, Mounir"

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Analysis of buckling stability behavior of hybrid plate using Ritz approach and numerical simulation
(Elsevier, 2021) Aguib, Salah; Chikh, N.; Kobzili, L.; Djedid, T.; Nour, A.; Meloussi, Mounir
In this article, we studied the instability phenomenon of plate buckling made of steel (E36-S355), and magnetorheological elastomer subject to compression loading. The study of the magnetic field intensity influence on the buckling instability of compressed hybrid plates is done by a mathematical development using the Ritz approach and by a numerical simulation under the Abaqus software. The obtained results show clearly that we can control the instabilities of the adaptive smart plate’s behavior by the magnetic field, and the orientation angle of pseudo-fibers formed by the iron particles; depending on the variation of the angle direction of the magnetic field
Dynamic characterization of the magnetomechanical properties of off axis anisotropic magnetorheological elastomer
(De Gruyter Open, 2022) Bendjeddou, Walid; Aguib, Salah; Chikh, Noureddine; Nour, Abdelkader; Djedid, Toufik; Kobzili, Lallia; Meloussi, Mounir
The use of magnetorheological elastomers in the mechanical and acoustic fields, by the automotive, aeronautical, and building industries, is currently developing strongly and rapidly. The perfect understanding of the capacity of smart insulation based on the absorption of the vibratory waves by magnetorheological elastomers materials passes by the knowledge of their dynamic mechanical behavior. In this present work, we have characterized the dynamic mechanical properties of the magnetorheological elastomer off axes anisotropy by the inclination, of different angles (15°, 30°, and 45°), of the pseudo-fibers of the iron particles formed by the application of a magnetic field at different intensities using an optimal loading rate of 30%. The rubber specimens were prepared by mixing micron-sized iron particles dispersed in room temperature vulcanized (RTV) silicone rubber by solution mixing. The experimental results obtained show a clear dependence of the effect of inclusion of ferromagnetic chains on the magnetomechanical properties. It is observed that the mechanical properties are better when applying a magnetic field of 0.6 T with an angle of inclination of 45°. The improvements added in this work could be useful in several industrial applications, such as automotive, aeronautic through adaptive control of damping and vibration level
Experimental analysis of the tensile behavior of a hybrid composite beam with adjustable mechanical properties
(Springer, 2022) Aguib, Salah; Chikh, Noureddine; Settet, Ahmed tidjani; Nour, A.; Meloussi, Mounir; Djedid, T.
Magnetorheological elastomer beam samples were tested in uniaxial tension in magnetic fields of different intensities up to the final rupture. The samples deformed nonlinearly. Their maximum elongation reached 70% and the tensile strength increased by 120% with growing intensity of magnetic field applied
Jet instability of suspensions of different shaped particles exhibiting discontinuous shear thickening
(Society of Rheology, 2022) Meloussi, Mounir; Schaub, S.; Ciffreo, A.; Aguib, Salah; Kuzhir, P.
This work is devoted to the detailed study of jet instability occurring in concentrated aqueous mixtures of calcium carbonate (CC) isotropic-shaped particles and rigid polyamide (PA) fibers. These mixtures exhibit very sharp discontinuous shear thickening (DST). The jets were subjected to a free fall under gravitational stretching at a constant flow rate. In the absence of PA fibers, we observed relatively strong lateral oscillations occurring for jet lengths L ≳ 6 cm and accompanied by small periodic undulations of the jet diameter. Two-dimensional Direct Fourier Transform analysis reveals approximately linear dispersion relations for propagation of lateral oscillations and diameter undulations with similar wave speeds ∼ 1 m / s. This instability is ascribed to complex rheological behavior in an extensional flow above the DST transition. Theoretical modeling reveals abrupt jumps of the tensile stress along the jet likely leading to fluctuation of longitudinal and transverse velocity fields within the jet perceived through jet diameter and centerline undulations. The addition of PA fibers to CC suspension damps lateral oscillations but favors ruptures along the jet. This is tentatively explained by the interplay between growing lower and decreasing upper DST threshold stresses with increasing fiber volume fraction φ f along with the thinning of the jet diameter down to the size of fiber flocs. Quantitatively, the stabilizing effect of PA fibers is manifested through an abrupt decrease in the lateral drift amplitude at φ f ≳ 0.75 vol %
Jets of discontinuously shear thickening suspension
(2020) Meloussi, Mounir; Kuzhir, Pavel; Aguib, Salah
In the present work, jets of discontinuously shear thickening (DST) suspension emerging from a vertical pipe have been experimentally studied. The suspension flows through the pipe under gravity at nearly constant flow rate and the stress field in the jet is mostly extensional with the stress levels governed by gravitational forces. The dynamics of the jet was recorded with a high-speed camera at 300 fps, then the recorded videos were discretized into pictures and carefully analyzed with a written and executed program in MATLAB, based on image processing. The suspension is a concentrated mixture of calcium carbonate (CC) microparticles dispersed in water at 68% volume fraction with addition of different concentrations of polyamide (PA) microfibers of 700μm x 15 μm in size. The CC suspension solely exhibits strong DST behavior characterized by a viscosity divergence above a critical stress. At a given flow rate, depending on the jet length (distance between the pipe outlet and a point where the jet hits the experimental table), different behaviors are observed varying between stable viscous thread to coiling instability and elastic instabilities with periodic rupturing of the jet ascribed to achievement of the critical stress of the DST onset under extensional deformations. Addition of fibers mainly stabilizes the jets and this effect is still not fully understood and perhaps depends on the flow-induced orientation of fibers under extensional flow, increasing extensional viscosity. In this communication we will discuss in detail different regimes and present experimental correlations between the fiber concentration and dynamic parameters of the jet instability (wavelengths, lateral oscillation amplitudes, etc.)
Measurements and identification of smart magnetomechanical elastomer composite materials properties in shear mode
(Institute of Physics Publishing, 2019) Nedjar, Ali; Aguib, Salah; Djedid, Toufik; Nour, Abdelkader; Meloussi, Mounir
Magnetorheological elastomer composite materials (MRE) are a new class of intelligent active materials composed of ferromagnetic particles, of micrometric size, dispersed in a silicone elastomer matrix, which exhibit variable stiffness and damping properties which are modifiable under the application of an external magnetic field. Currently, these devices are primarily used in automotive and building applications, but they can easily be adapted to meet the requirements of aerospace applications. The development process and experimental characterization needed to evaluate the active control performance of this material have been made. This is done by characterizing the mechanical properties as a function of the magnetic field, as a function of the excitation frequency and as a function of the different percentage of ferromagnetic particles loading. An example of application of this material in aeronautics is also presented
Rheology of concentrated suspensions of spherefiber fiber mixtures in view of applications to reinforced cementitious materials
(Université M'Hamed Bougara : Faculté de Technologie, 2022) Meloussi, Mounir; Khzhr, Pavel(Directeur de thèse); Aguib, Salah(Directeur de thèse)
Discontinuous shear thickening (DST) in dense non-Brownian suspensions is a welldocumented phenomenon in scientific research, however its origins and effects are still under discussion nowadays. Not being able to recognize the direct cause of the phenomenon represents a point of weakness in many industrial fields, especially in the field of concrete and fiber reinforced concrete production. In this thesis, we will study experimentally as well as theoretically the DST in a suspension of calcium carbonate microparticles loaded with rigid polyamide and glass fibers. The rheology of this suspension simulates the behavior of fiber-reinforced concrete. We reproduce on a reduced scale different types of flows occurring in the concrete placement process, such as double-helix mixing, pumping through tubes, jet flow at the tube outlet, and we derive fundamental rheological behaviors applicable to any type of "sphere-fiber" mixtures. Using "mixing" type rheometry (double helix tools adapted to the rotational rheometer), we will first show that the addition of fibers shifts the DST transition to lower critical shear rates, which is explained by an increase in the viscosity of the suspension, so that the shear rate to reach the DST onset stress decreases. However, the mixture jams at a fiber volume fraction greater than or equal to 4% vol which is interpreted in terms of the percolation threshold of the fiber network in the shear thickening matrix of calcium carbonate. We will show in a second stage that the rheological behavior in a flow induced by a pressure gradient through a capillary remains quite similar to that in a simple shear but only at low fiber volume fractions ?? ? 1 % vol, and if the Mouney-Rabinowitch correction is correctly applied. Above this volume fraction, the flow ?? curves in the capillary rheometry become very different from those measured in simple shear likely because of microstructural difference in two different flow geometries. The theoretical model based on the homogenization approach allows to reproduce at least semi-quantitatively the flow curves in the " mixing" type and capillary rheometry at low fiber volume fractions but fails to capture microstructural changes at higher volume fractions. Finally, the instabilities of the calcium carbonate suspension jet under gravity with and without polyamide fibers will be studied. This instability is manifested by strong lateral oscillations of the axial symmetry axis of the jet accompanied by a slight undulation of the jet surface. We will perform for the first time a two-dimensional direct Fourier transform (2D DFT) analysis of the spatiotemporal variation of the jet diameter and the lateral deflection of the jet in the DST regime. We will show that the addition of polyamide fibers at different concentrations in the suspension allows for jet stability and promotes jet fractures. A theoretical explanation for the onset of jet lateral instability and the stabilizing effect of the fibers will then be developed based on the evaluations of tensile stresses and the lower and upper thresholds of the DST.