Publications Scientifiques

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Author: search.filters.author.Chellil, Ahmed

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    Effect of repair patch nature on J-integral reduction in notched plates
    (Emerald Publishing, 2024) Houari, Amin; Kouider, Madani; Polat, Alper; Amroune, Salah; Mohamad, Barhm Abdullah; Chellil, Ahmed; Campilho, Raul
    Purpose: The purpose of this research is to evaluate the effectiveness of different repair patch materials in reducing the stresses at the crack tip of a 2024-T3 aluminum plate. This involves a numerical analysis using the finite element method (FEM) to estimate the reduction in the J-integral value, with the goal of identifying how various parameters related to the patch materials, adhesive properties and loading conditions influence the structural integrity of the repaired plate. Design/methodology/approach: The methodology of this research involves conducting a numerical analysis using the FEM to estimate the reduction in the J-integral value at the crack tip of a 2024-T3 aluminum plate. Three types of patches – metal, composite and functionally graded material (FGM) – were examined under tensile loading conditions, and Adekit-A140 adhesive was used to bond these repair patches to the aluminum plate. Findings: The analysis considered various parameters, including crack length, the nature of fibers in the composite material, the gradation exponent for FGM patches and the nature of the face in contact with the adhesive for the FGM patch. Additionally, stress analysis was conducted, examining the J-integral values for the plate, shear stress in the adhesive layer and peel stress in the composite patch. The findings highlight that modifying the nature of the repair patch used can significantly enhance the structural integrity of the repaired plate. Originality/value: The study analyzed J-integral values, shear stress in the adhesive and peel stress in the composite patch. Various parameters, including crack length, fiber type, gradation exponent and adhesive contact face nature, were considered. Results demonstrate that the J-integral value can be significantly reduced by altering the repair patch type, highlighting the effectiveness of customized patch materials in enhancing structural integrity.
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    An algorithmic approach for the distribution of the blades of a gas turbine rotor
    (Editura Politechnica, 2024) Houari, Amin; Amroune, Salah; Chellil, Ahmed; Madani, Kouedar; Saada, Khalissa; Farsi, Chouki
    Our study focuses on the critical steps of balancing and maintaining the turbine rotor in electricity production companies. We aim to develop a MATLAB program for blade distribution to optimize the turbine's performance. We conducted practical tests using the BLADIS software from a major company in the field and compared it with the test data from our program. We performed three blade distribution experiments using the initial static moment values of each blade, which the MEI Company's (Sonelgaz-M'sila) electronic balance provided. Our main objective is to propose a new algorithm for turbine rotor blade distribution using a MATLAB subroutine that remains applicable during maintenance operations, including punctual blade changes. This proposed algorithm will help improve the turbine rotor's efficiency and performance. Electricity production companies to maintain their turbines and optimize energy output can use our study’s findings and algorithm. By implementing our proposed algorithm, companies can save costs and increase their energy efficiency, making them more competitive in the market.
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    Experimental Investigation Into the Tensile Strength Post-Repair on Damaged Aluminium 2024 -T3 Plates Using Hybrid Bonding/Riveting
    (Sciendo, 2024) Merah, Abdelkrim; Houari, Amin; Madani, Kouider; Belhouari, Mohamed; Amroune, Salah; Chellil, Ahmed; Yahia, Cherif Zineelabidine; Campilho, Raul D.S.G. Duarte Salgueiral Gomes
    Since the implementation of repair processes by composite patch bonding, this process has consistently demonstrated high performance across various industrial sectors, especially in the fields of aeronautics, aerospace and civil engineering. Consequently, there are situations in which the riveting process becomes the sole solution, particularly when the structure is subjected to severe mechanical or thermo-mechanical stresses, since adhesives have low mechanical strength after aging. Each method has its own set of advantages and disadvantages. The current trend is to combine these two processes to minimise their drawbacks as much as possible. The objective of this work is to present an experimental study on the repair of an aluminium plate AL2024-T3 with a central circular notch using a patch of different nature (metal or composite), under tensile loading conditions. The repair composite considered is a carbon/epoxide. The results of the tensile tests showed that the repair by the combination of the two processes improves the mechanical strength of the damaged structure. A comparison of the results of the experimental curves obtained on riveted, bonded and hybrid assemblies has been taken into consideration.
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    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.
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    Experimental investigation into the tensile strength post-repair on damaged Aluminium 2024 -T3 plate using hybrid bonding/riveting
    (2024) Merah, Abdelkrim; Houari, Amine; Madani, Kouider; Belhouari, Mohamed; Amroune, Salah; Chellil, Ahmed; Yahi, Cherif Zineelabidine; R.D.S.G., Campilho
    Since the implementation of repair processes by composite patch bonding, this process has consistently demonstrated high performance across various industrial sectors, especially in the fields of aeronautics, aerospace and civil engineering. Consequently, there are situations in which the riveting process becomes the sole solution, particularly when the structure is subjected to severe mechanical or thermo-mechanical stresses, since adhesives have low mechanical strength after aging. Each method has its own set of advantages and disadvantages. The current trend is to combine these two processes to minimize their drawbacks as much as possible. The objective of this work is to present an experimental study into the repair of an aluminum plate AL2024-T3 with a central circular notch using a patch of different nature (metal or composite), under tensile loading conditions. The repair composite considered is a carbon/epoxide. The results of the tensile tests clearly showed that the repair by the combination of the two processes clearly improves the mechanical strength of the damaged structure. A comparison of the results of the experimental curves obtained on riveted, bonded, and hybrid assemblies has been taken into consideration.
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    Impact Behavior Analysis of Luffa/Epoxy Composites Under Low-Velocity Loading
    (Springer Nature, 2024) Grabi, Massinissa; Chellil, Ahmed; Lecheb, Samir; Grabi, Hocine; Nour, Abdelkader
    Luffa cylindrical (LC) has an exceptionally multipartite architecture, a hierarchical and light structure, and a low density. Such a structure is potentially suitable to replace conventional porous-type composites for low-energy absorption and material reinforcement applications. This paper presents an experimental study of the impact behavior of four different luffa/epoxy composites, named (A), (B), (C), and (D) subjected to low-velocity impact (LVI) at energies ranging from barely visible impact damage (BVID) to perforation (5,15, and 20J). Acoustic emission (AE), scanning electron microscopy (SEM), and digital image correlation (DIC) were introduced to the indentation test to offer additional information on damage mechanisms and on strain and displacement fields since the LVI test has a short duration and real-time damage monitoring is not always achievable. The results showed that the values of the peak force of laminates (A), (B), and (D) are relatively lower compared to laminates (C). In the case of perforation impact energy (20J), the Coefficients of Restitution (CoR) of composites (A), (B), and (D) are equal to 0, which indicates that the nature of the impact is completely plastic, except for composite (C) had a value of 0.11, and a lower degree of damage at all impact energies. Composites (C) exhibit the highest impact resistance, followed by composites (A), while composites (D) display the highest energy absorption, followed by composites (B). Multivariable statistical analysis of the AE signals identified four classes of damage: matrix cracking, fiber-matrix debonding, delamination, and fiber breakage. The damage modes found by AE are well presented and proven by SEM analysis. The luffa fiber-reinforced composite has better impact properties than other natural fiber-reinforced composites.
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    Failure Prediction of Laminated Composites: Simulation of the Nonlinear Behavior and Progressive Damage
    (Korean Fiber Society, 2023) Bensalem, Abdelhafid; Daoui, Abdelhakim; Cheriet, Abderrahmane; Lecheb, Samir; Chellil, Ahmed; Kebir, Hocine; Aissani, Linda
    The Hashin’s criteria are useful in composite structural applications because of their simple concept and their theoretical results are relatively close to that got in the experimental parts. In the present study, in the present study, the failure of the composite laminates under static loading have been developed predicted using Hashin’s Criterion. Nonhomogeneous stresses within a structure may induce a complicated failure scenario whereby one ply at a point can initiate failure and can affect also other plies at the same point or the same ply in different neighboring points. With neglecting the possibility of interlaminar failure, only in-plane loads are considered in this state. The results showed that the failure analysis was proposed to simulate the nonlinear laminate behavior and progressive damage of selected laminates under to their ultimate strength. In our approach, the finite element analysis is performed using MATLAB software to study the effect of tensile and compressive loading on the failure of epoxy resin laminate AS4/3501-6.
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    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.
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    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.
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    Book Abstract
    (Université M'Hamed Bougara Boumerdes : Faculté de Technologie :Département Génie Mécanique, 2021) Chellil, Ahmed; Yahi, Mostepha; Saidi, Mohamed
    La conférence de la Mécanique et Maintenance regroupe tous les acteurs du domaine dans un espace en ligne, a pour but principal de renforcer la communication entre la famille de l’enseignement supérieur et les industriels, rapprocher le secteur socio-économique avec les compétences académiques et l'administration publique. Notre objectif est de mettre en place un écosystème national favorable à l’investissement, par la communication entre les secteurs concernés. Aussi nous souhaitons à travers cette conférence, tracer une feuille de route qui pousse l'économie et le développement national vers le progrès.