Browsing by Author "Mechakra, Hamza"

Now showing 1 - 18 of 18

An advanced dynamic repair of edge crack aluminum plate with a composite patch
(Trans Tech Publications Ltd, 2014) Lecheb, Samir; Nour, Abdelkader; Chellil, Ahmed; Mechakra, Hamza; Amarache, A.; Kebir, H
In this work, repaired crack in 2024 T3 aluminium plate with composite patch is presented, the problem is handled in plane stress condition under tensile Mode I crack growth. In the numerical simulation, firstly we determine the displacement, strain and stress, also the first six mode shapes of the plate, secondly we compare the first results with result of a cracked plate, thirdly we repair the crack with composite patch for different materials (Glass, Boron, carbon) and for (2 layers, 4 layers). Finally the comparison of stress, strain, displacement and six first natural frequencies between uncracked, crack initiation and composite patch repair crack. The best offer operating according to the need is selected
An Ecological Cement Mortar Produced by Using Nanosilica and High Content of Metallurgical Waste Slag: Rheological, Mechanical, and Chemical Durability Study
(SAGE, 2025) Phan, Vu To-Anh; Mechakra, Hamza; Saidi, Mohammed
This study investigates the possibility of using a high content of ground granulated blast furnace slag (GGBS) with a fixed content of nanosilica (NS) to produce a sustainable cement mortar that can reduce carbon emissions. The synergistic effects of GGBS and NS on the rheological and thixotropic behavior of cement pastes, their chemical durability, and the mechanical properties of mortars were investigated. Cement paste blends and mortars incorporating GGBS were investigated, with and without the addition of NS. The results show that the rheological behavior and the thixotropic characteristics of studied cement pastes were significantly changed in the presence of NS. In phase 1, the GGBS-based cement pastes exhibited shear-thinning behavior, leading to a decrease in viscosity. Gradually, the shear rate increased to the level observed at rest (in phase 2). Using 66% GGBS with 2% NS can produce an ecological mortar with a compressive strength exceeding 55 MPa at 28 days. Moreover, stress-strain curves can show acceptable mechanical behavior of GGBS-based mortar with 66% cement substitution. Incorporating a considerable quantity of GGBS, about 66%, can lead to acceptable results in the two aggressive media (nitric acid [HNO3] and hydrogen chloride [HCl]) looking at their chemical and mechanical resistance.
Damage diagnostic of ball Bearing using vibration analysis
(Université M'Hamed Bougara Boumerdes : Faculté de Technologie, 2021) Belaid, Siham; Lecheb, Samir; Chellil, Ahmed; Djellab, Amira; Mechakra, Hamza; Kebir, Hocine
Maintenance of any machinery is very important in view of downtime of machinery. The bearing sector is one of the examples without which not single rotating machinery work, Our work is devoted first to a study of static behavior by determining the stress, strain and displacement, then dynamic behavior by determining the first four naturals frequencies. Secondly the dynamic analysis of the Bearing with defect as a function of crack size and location. Finally, the analysis of the results obtained in terms of residual parameters, allow us to draw a roadmap for the diagnosis and maintenance of bearings.
Dynamic modeling of milling and effect of tool path on machining stability
(Springer, 2022) Ikkache, Kamel; Chellil, Ahmed; Lecheb, Samir; Mechakra, Hamza
Regenerative stability theory predicts a set of optimal, stable spindle speeds at integer fractions of the natural frequency of the most flexible mode of the system. Being able to predict these phenomena therefore makes it easier to choose cutting conditions to increase productivity. The three-dimensional study of milling with a spherical tool has been done, and a part of complex shape, it is the continuation of our work previously published. Recently, several theoretical models have been developed for various applications, but there have been very few studies on the particular case of three-axis, complex shape milling. In this paper, it is planned to study the stability of milling operations with a hemispherical tool, using differential equations with delay terms. In this paper, based on the 3D study using a different model, new parameters are introduced in order to compare it with the 2D study of the paper previously published. For a 6061-T6 aluminum alloy part, the model is based on the method of discretization by delay terms of the dynamic equation. Our work has been devoted to have the machining stability lobes in 3D format, along the entire trajectory (discretized in several interpolation segments) of the tool for a flat, inclined (ascending or descending) and complex shaped surface
Dynamic prediction fatigue life of composite wind turbine blade
(Techno Press, 2015) Lecheb, Samir; Nour, Abdelkader; Chellil, Ahmed; Mechakra, Hamza; Ghanem, Hicham; Kebir, Hocine
Effect of nanosilica-doped superplasticizer on the properties of cement mortars
(STEF92 Technology, 2023) Safi, Brahim; Mechakra, Hamza; Saidi, Mohammed; Lecheb, Samir
Recently, nanotechnology has attracted a considerable scientific interest due the potential new uses of non-particles, which can improve the properties of cement mortars or concretes, such as Nanosilica. Nanoparticles, like those of nanosilica, have been shown to have unique physical and chemical properties different from those of conventional cement additions. Nanosilica was used either to replace part of the cements or as an addition to improve the performance of the cement such as accelerating the hydration of the cement phases. This work investigates the effect of nanosilica adding to superplasticizer on fresh and hardened properties of cement mortars. For this, three superplasticizer types of three different firms doped with nanosilica (NS) at 1.5% wt. of superplasticizer (SP) to estimate the effect of nanosilica-based superplasticizer on the properties of cement mortars in the fresh and hardened state. An experimental study was conducted to evaluate the three SP based on NS on fresh and hardened properties. Our results show that nanosilica is compatible with the three superplasticizer, what is remarkable on the mortars in the fresh state, with a good workability which is between (24cm and 28cm) and a total absence of segregation which acts on the mechanical properties of the self-consolidating mortar in (3,7 and 28 days).
Effect of stitch orientation on tensile and flexural bending mechanical properties and damage mechanisms of Glass/Epoxy laminated composites
(2021) Mechakra, Hamza; Lecheb, Samir; Chellil, Ahmed; Safi, Brahim
In this study, the effect of stitch row directions on tensile and flexural bending mechanical properties of composite laminates reinforced by glass-fabric was experimentally investigated. For the fabrication of stitched laminates a polyester thread used to stitch the dry fabric glass in fourth cases (longitudinal stitch 0°, transversal stitch 90°, multi-stitching 0°/90° and 45°/-45° stitch) with 4 mm stitch spacing. The responses of stitched laminates specimens subject to the tests mentioned was compared to the unstitched laminates and discussed. According to our results, the effect of stitching plays of opposite roles on tensile property by decreasing of about 45% and 36% in tensile strength and longitudinal modulus compared to unstitched specimens, respectively. However, an increasing approximately 11.69% to 20.25% in flexural strength found in specimens stitched along 0° and multi-stitching 0°/90°, due to the stitch lines through thickness by arrests temporally of cracks propagation and the delamination progressively propagate between layers.
Evaluation of Viscoelastic Performance and Molecular Structures of Natural Rubber/NBR Blends Reinforced by Carbon Black and Nano-Silica
(Periodica Polytechnica, 2024) Chelli, Amel; Mechakra, Hamza; Chellil, Ahmed; Tria, Djalel Eddine; Bessa, Wissam; Ikkache, Kamel; Safi, Brahim
This study focuses on the evaluation of the dynamic mechanical properties, molecular structure, density, hardness, swelling behavior of natural rubber blends (NR) and nitrile rubber (NBR) reinforced with carbon black and/or nano-silica. An experimental work has been conducted to study of the effects of increasing NR content and incorporating nano-silica on the mechanical properties and molecular structure were studied using dynamic mechanical analysis (DMA) and Fourier transform infrared (FTIR) spectroscopy. The results show that increasing the NR content and/or incorporating nano-silica into the elastomer leads to a higher storage modulus with no significant change in the glass transition temperature. FTIR analysis indicates the compatibility of the polyblends and the presence of oxidation of the main polymer chain generated during the grinding of the rubber. Additionally, the results of the swelling study demonstrate that stronger molecular interactions occur on the surface of the nano-silica between the nitrile radicals in the NBR and the silanol (Si-OH) radicals. These findings suggest that blending NR and NBR with carbon black and/or nano-silica can improve the mechanical properties and compatibility of the resulting polyblends, with potential applications in the development of advanced elastomeric materials.
Experimental and numerical investigation of impact behavior in honeycomb sandwich composites
(SAGE, 2024) Djellab, Amira; Chellil, Ahmed; Lecheb, Samir; Safi, Brahim; Mechakra, Hamza; Houari, Amin; Kebir, Hocine; Madani, Kouider
This paper presents an experimental and numerical study on the low-energy impact fatigue and bending behavior of sandwich panels reinforced with composite laminate glass and carbon fabric facesheets, supported by a honeycomb core made of Nomex. The crushing behavior of honeycomb sandwich specimens subjected to the impact test was compared and discussed. Our results indicate that the carbon composite facesheets have a significant effect on the impact, resulting in an increase in impact resistance and a 157.14% increase in crack depth in the elastic region compared to glass facesheets reinforcement. This increase serves as an indicator of the laminate's ability to resist damage initiation and impact fracture mechanisms. Also, an increasing in flexural strength about 45.72% was observed in carbon facesheets honeycomb specimens compared to glass facesheets reinforcement. Microscopic illustration of the damaged honeycomb sandwich specimens was conducted to evaluate the interfacial characteristics and describe the damage mechanics of the composite facesheets and core adhesion under the impact test. The numerical approach proves to be efficient in terms of accuracy and simplicity compared to existing methods for predicting the damage mechanisms of honeycomb sandwich structures. It was noted that results of numerical study show best agreements with experiment results and the model can be used to predict the low-energy impact fatigue.
Fatigue study of composite materials with short vegetal fiber reinforcement
(2015) Mechakra, Hamza
This research concerns the characterization of the mechanical behavior of composite materials reinforced with different percentage of short natural fibers Alfa chemicllly treated and untreated in the polymer matrix Polypropylene (PP). Adherence at the fiber/matrix interface (hydrophilic / hydrophobic) was studied. The various means and implementation techniques used in this study are: crushing, alkali treatment, extrusion and injection. The experimental tests such as static tension, charge-discharge, have given a significant number of physicochemical information of the composite material, which allowed us to compare with other composite materials. This process has generated a referenced database that can be useful for others composites from the same family of composites based on natural fibers. Thus, damage mechanisms were identified by mechanical tests and observations with scanning electron microscope (SEM). The acoustic emission (AE) is used to detect the damage. Through this technique can be evaluate the quality and importance of the fiber/matrix interface with optimization of chemical treatment and reduce of bundles fibers diameters that are a fundamental technique for this study and has given greater improvements in mechanical properties composites. Several experimental tests were performed on three types studied in static materials, allowed to better understand the fatigue behavior of the material. The Mori-Tanaka model was used to validate the experimental results. The elastic behaviors have been studied with the aim of determining different intrinsic mechanical properties of the material
Incorporation mode effect of Nano-silica on the rheological and mechanical properties of cementitious pastes and cement mortars
(2018) Saf, Brahim; Aknouche, Hamid; Mechakra, Hamza; Aboutaleb, D.; Bouali, Khaled
International conference on advanced mechanics and renewable energies abstracts book
(Belaidi Idir, 2018) Belaidi, Idir; Mechakra, Hamza; Alem, Said; Lounici, Mohand Said
Mechanical characterizations of composite material with short Alfa fibers reinforcement
(Elsevier, 2015) Mechakra, Hamza; Nour, Abdelkader; Lecheb, Samir; Chellil, Ahmed
Modeling a Composite Reinforced with Short Alfa Fibers to Determine its Fatigue and Structural Homogenization
(Springer, 2018) Nour, Abdelkader; Mechakra, Hamza; Benkoussas, B.; Tawfiq, I.; Settet, A. T.; Renane, R.
The fatigue and homogenization of polypropylene reinforced with untreated and chemically treated short Alfa fibers were investigated using a modified Mori–Tanaka model. The polypropylene with chemically treated fibers showed a higher resistance than that with untreated ones. Cylindrical fibers with elliptical cross sections were used in experiments. Their mechanical characteristics were determined by the inverse method.
Optimization of small horizontal axis wind turbines based on aerodynamic, steady-state, and dynamic analyses
(MDPI, 2023) Deghoum, Khalil; Gherbi, Mohammed Taher; Sultan, Hakim S.; Mechakra, Hamza
In this article, the model of a 5 kW small wind turbine blade is developed and improved. Emphasis has been placed on improving the blade’s efficiency and aerodynamics and selecting the most optimal material for the wind blade. The QBlade software was used to enhance the chord and twist. Also, a new finite element model was developed using the ANSYS software to analyze the structure and modal problems of the wind blade. The results presented the wind blade’s von Mises stresses and deformations using three different materials (Carbon/epoxy, E-Glass/epoxy, and braided composite). The modal analysis results presented the natural frequencies and mode shapes for each material. It was found, based on the results, that the maximum deflections of E-glass, braided composite and carbon fiber were 46.46 mm, 33.54 mm, and 18.29 mm, respectively
Proceedings of the 4th International Symposium on Materials and Sustainable Development
(Springer, 2020) Safi, Brahim; Daoui, Abdelhakim; Mechakra, Hamza; Ghernouti, Youcef
This book presents the proceedings of the 4th International Symposium on Materials and Sustainable Development ISMSD2019 (CIMDD2019). Organized by the Research Unit: Materials, Processes and Environment (www.urmpe.dz) and University M'hamed Bougara of Boumerdes, this symposium follows the success of CIMDD 2013-2015-2017 and continues the traditions of the highly successful series of International Conferences on the materials, processes and Environment. The Symposium is a unique topical forum to share the latest results of the materials and sustainable development research in Algeria and worldwide
RHEOLOGICAL AND MECHANICAL BEHAVIOR STUDY OF ECO-FRIENDLY CEMENT MORTAR MADE WITH MARBLE POWDER
(University of Zielona Gora, 2024) Chahour, Kahina; Mechakra, Hamza; Safi, Brahim; Dehbi, Nacera-Melissa; Chaibet, Cylia
The work aim is to investigate the rheological and mechanical behavior of an eco-friendly mortar made with marble powder. Marble is have used as sand (total substitution of natural sand) and as an additional material (partial substitution of cement). Firstly, rheological tests were carried out on the cement pastes in order to study the effect of cement substitution by marble powder on the rheological behavior. Secondly, our study is devoted to evaluate the mechanical performances (flexural strength, compressive strength, mechanical behavior and ultrasonic pulse velocity) of a fluid mortar such as the case of the self-compacting mortars elaborated with the marble powder as an addition a material and as sand. The mechanical test results show that compressive strength and mechanical behavior of an ecological cement mortar made with marble waste as natural sand improved significantly. However, marble-based mortars with 100% of marble sand have given a mechanical strength similar to that obtained by control cement mortar (100% natural sand). It was also noted that it an ecological cement mortar made with 30% of marble powder as an addition a supplementary material can be obtained. This leads to a reduction in cement consumption and a reduction in CO2 gas emissions caused by cement production.
Topological optimization of dimple distribution for enhanced performance in hydrodynamic porous self-lubricating journal bearings with sealed ends
(Sage, 2025) Ifrah, Walid; Manser, Belkacem; Chellil, Ahmed; Ragueb, Haroun; Mechakra, Hamza; Khelladi, Sofiane; Belaidi, Idir
This study numerically investigates the impact of optimal textures location on the performance of hydrodynamic porous self-lubricating journal bearings with sealed ends, subjected to a stationary load. The analysis employs a modified Reynolds equation coupled with Darcy’s law to model fluid flow in both the lubricating film and the porous matrix, considering the hydrodynamic self-lubrication problem. The governing nonlinear PDE systems were solved numerically using the finite difference method, combined with Reynolds boundary conditions and continuity conditions for velocity and pressure at the film-bush interface. A Binary Genetic Algorithm (BGA) is employed to optimize the topological distribution of square dimples in the textured porous layer to enhance bearing performance. The study investigates the influence of key parameters, including applied load, rotational speed, permeability, and texture depth, on bearing characteristics such as minimum film thickness and friction coefficient. Results show good agreement with benchmark data and indicate a positive enhancement in porous bearing performance. In addition, findings demonstrate that increasing the permeability of the porous structure reduces bearing performance (up to 25% in minimum film thickness and 8% in friction coefficient). However, the application of the optimization technique identified an optimal arrangement of textures that compensates for these performance losses, even under severe working conditions. Texturing the outlet region of the contact (beyond 180°) at the cavitation zone causes a micro-step bearing mechanism, generating localized pressure recovery within the textured area, significantly enhancing the minimum film thickness (up to 12%), reducing friction (up to 23%), and minimizing cavitation (up to 24%).