Browsing by Author "Chellil, Ahmed"

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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
Aeroelastic stability analysis of composite rotor blade
(IEEE, 2013) Chellil, Ahmed; Settet, A.T.; Lecheb, Samir; Nour, Abdelkader
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.
Alkaline Treatment’s Effect on Mechanical Properties and Damage Assessment Through Acoustic Emission of Luffa Fiber Composite
(Springer, 2022) Grabi, Massinissa; Chellil, Ahmed; Habibi, Mohamed; Laperriere, Luc
Improving the mechanical properties and reduced damage of natural fiber-reinforced composites can contribute to their increased use in various fields. In this paper, an experimental study describes the effect of alkaline treatment of two different concentrations of 2 % and 5 % NaOH for one hour on the mechanical performance and damage of luffa fiber composites. Three different composites reinforced with treated and untreated luffa fibers were developed using the resin transfer molding (RTM) process. The specimens were coupled with acoustic emission during tensile tests, to monitor and evaluate damage mechanisms. The tensile test results showed that the alkaline treatment of 5 % improved tensile strength, which reached 81.08±1.48 MPa. However, the 2 % treatment improved Young’s modulus with 8.94±0.5 GPa. In comparison, T2 % and T5 % composites provided the best results for mechanical properties compared to NT composites. Four classes of damage mechanisms have been identified using the K-means clustering method, including matrix cracking, fiber pull-out, delamination, and fiber breakage. The cumulated energy and hits of the 5 % treated composite was lower than the untreated and 2 % treated, which means less damage to the T5 % specimen. Scanning electron microscopy (SEM) pictures of the tensile fractured surfaces of luffa fiber composites treated with 5 % NaOH, revealed good adhesion between the fibers and the matrix. The AE results are convincing, and they were confirmed by SEM pictures of the specimens’ fractured faces, which revealed the main causes of material failure, So, based on the AE results and mechanical properties, T5 % composite is preferable.
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.
Characterization of low-velocity impact and post-impact damage of luffa mat composite using acoustic emission and digital image correlation
(SAGE Publications, 2022) Grabi, Massinissa; Chellil, Ahmed; Habibi, Mohamed; Grabi, Hocine; Laperriere, Luc
In this paper, low-velocity impact and compression after impact damage tolerance of composite reinforced with natural luffa mat were studied for the first time. The effect of impact energy and the influence of the damaged area on the residual mechanical properties under compression were investigated. Acoustic emission (AE), digital image correlation (DIC) and scanning electron microscopy (SEM) were used for the evolution of different damage modes and displacement fields. The findings of the experiments reveal that compression after impact tests of 1, 2, and 3J show a significant effect of the residual damage which decreases residual compressive strength by 12.61, 24.14, and 30.9%, respectively, compared to the unimpacted composite, but Young’s modulus was not significantly affected. Multivariable statistical analysis of the AE signals identified four classes of damage: matrix cracking, fiber-matrix debonding, delamination, and fiber failure. It also showed that the damage mode of unimpacted composites which presents the majority of the amplitude events of the AE signals is mainly due to fiber failure, by contrast, for impacted composites the damage mode is mainly due to fiber-matrix debonding. The AE results are convincing and they were confirmed by SEM images of the fractured faces of the specimens, which revealed the main causes of material failure during the compression after impact test. The DIC system monitored the effect of pre-existing damage under compressive loading and found that increasing impact energy increases the stress concentration around the impacted area and has a significant effect on residual crack development, much more in the loading direction
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 Behavior of Functionally Graded Turbine Blade Using Numerical Modeling
(Springer, 2025) Houari, Amin; Guemmour, Mohamed; Amroune, Salah; Chellil, Ahmed; Nour, Abdelkader; Kouider, Bendine; Madani, Kouider; Campilho R.D.S.G.
Turbine blade performance degrades under dynamic stresses from high temperatures and vibrations. design is challenging due to material limitations. Designers must minimize stresses, especially centrifugal forces, within acceptable material limits. the complex nature of these blades requires a seamless integration of design, material selection, and manufacturing processes to achieve the highest performance. thus, graded material properties are essential to control their behavior and ensure the longevity of the turbine blades during operation. this project aims to develop novel metal/ceramic functionally graded material (fgm) blade designs to enhance the lifespan of gas turbine rotors. A numerical study using the mesh method (umm) with the abaqus code will produce a 3d graded multifunctional material with controlled strength under different loading conditions. Our numerical analyzes of the behavior of a blade was carried out in two parts. The first studies the static behavior, using the tto homogenization method to define the elastoplastic zone of the fgm and a damage criterion for the fgm up to failure via the xfem technique. The second part analyzes the vibration behavior of the blade, considering various parameters such as the direction of the distribution of the fgm’s material properties according to thickness, and the effect of combinations of metals and ceramics, characterized by the exponent n of the power law. Numerical analyses using abaqus code for the metal model were validated experimentally. Analyzes of the fgm design has confirmed its validity in relation to the metal model. The results emphasize the importance of the distribution of material properties in fgm blades that significantly affect the stress distribution and modal analysis.
Dynamic behavior to fatigue crack initiation of a glass/epoxy laminate
(Trans Tech Publications, 2014) Lecheb, Samir; Nour, Abdelkader; Chellil, Ahmed; Lechani, R.; Kebir, H.
This paper based to study of the dynamic and fatigue behaviors with numerical and experimental parts of a composite material manufactured by stacking two layers of E-glass fiber in different angle orientations (0°/90°) immersed in polyester resin with total thickness 1.39mm. In Finite Element Analysis (FEA) using ABAQUS was used to evaluate the maximal (displacement, strain and stress) and the natural frequencies (mode shapes) of composite behavior under crack initiation condition. In the experimental part the laminate plate specimen with two layers is tested under one types of cyclic load in fully reversible tensile at (R=0), the fast fracture occur phenomenon and the fatigue life are presented, the fatigue testing exerted in INSTRON 8801 machine.
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 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.
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.
Effects of the geometrical parameters of the core on the mechanical behavior of sandwich honeycomb panel
(2019) SETTET, Tidjani Ahmed; Aguib, Salah; Djedid, Toufik; Chikh, Noureddine; Chellil, Ahmed
The present work is the study of mechanical behavior due to variation of the geometrical parameters in the core of the sandwich honeycomb panel. This study has allowed us to increase or decrease the strains and stresses of the panel, in changing the angle of alveolus, as explained and described below. In taking into consideration the results obtained previously to improve the mechanical properties and increase the adhesion of different parts of the panel, without changing the adhesive, we have conceived two new models, in increasing the contact surfaces in boundary of each part of the panel and giving a conical hexagonal shape in his corp
Etude des charges aéroélastiques d'une pale en composite
(2013) Chellil, Ahmed
Le but de ce travail est d'étudier le système des articulations de la pale des amortisseurs hydrauliques et en élastomère pour réduire le niveau vibratoire dans les rotors d'hélicoptères. Ces amortisseurs comprennent des moyens de rappel élastique à raideur et amortissement déterminés, pour éviter les phénomènes de résonance, en particulier de résonance de trainée et aussi de résonance de battement qui peuvent apparaître notamment sur les pales d'hélicoptères. En premier lieu une étude du comportement dynamique du système rotor avec les différents modes de vibrations et évaluation des contraintes des pales est établie. En deuxième lieu un modèle non linéaire identifiant les contraintes aéroélastiques en fonction de la rigidité du fuselage est simulé. Une modélisation en trois D par éléments finis de la structure en fonction des caractéristiques mécaniques du matériau et des charges aéroélastiques est présentée. Les calculs numériques sur le modèle développes tenant compte de l'interaction aéroélastique prouve que les amortisseurs en élastomère de type viscoélastique donne des meilleurs résultats par rapport aux autres hydrauliques. Une simulation numérique de la fissure sous les charges aérodynamiques sur la pale est présentée. Ce qui a permis de mettre en évidence un indicateur pour la surveillance et la prédiction de l'endommagement dans les pales d'hélicoptère. Enfin expérimentalement le choc dynamique d'impacts, a montré clairement la variation des propriétés mécaniques (la fréquence propre, la rigidité et le facteur d'amortissement) sous l'influence de la propagation de la fissure
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.
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.
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.
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.