HOCINE Makri

Mahmoudi Rim , Mahmoudi Hafida

Etude de conception d’un dispositif de prise de pièces a parois minces déformables

Allal Yacine , Mekki Aissa

Contribution à la conception d’une machine d’essai de fatigue pour éprouvettes plates

Fali daoud , Gana Abdelkader

ELABORATION DES COMPOSITES LAMINAIRES

Allouani Larbi , Bouzid Abdelbasset

ETUDE D’UN ROBOT SERIEL

Chebabhi messaoud , Benmekki

RELATION DURETE - PROPRIETES MECANIQUES DANS LES MATERIAUX CERAMIQUES

ZOUAK ANFAL , BENATTIA MALIKA, KORICHI LEILA

ETUDE MICROSTRUCTURALE DU SOUDAGE DES ACIERS.

BOUREZK IBRAHIM , GHADRI OUALID

INFLUENCE DE LA MICROSTRUCTURE SUR LES PROPRIETES MECANIQUES DES ACIERS SOUDES

GUENFOUD Mohamed , BERRA Mounir

Rénovation des coussinets pour les turbines à gaz

SAADA Abdelhaq , ABI Chakib

Synthèse bibliographique sur les composites biodégradables

MADI Abdelaziz , ROUBI Mohamed-Abderrahmane

Synthèse bibliographique sur les méthodes d’extraction des fibres végétales.

ABDELLAOUI Abdelkader , SAAD Moustapha

SYNTHÈSE BIBLIOGRAPHIQUE SUR L’USINAGE DES COMPOSITES

Kermiche Abdel Fettah , MILI Hacene

Etude et réalisation d’une machine d’essai de fatigue pour pièce soudé

Benabderrazag Khalil

CONTRIBUTION A LA REALISATION D’UNE MOCN

BAALI Selma

Contribution a l'etude du delaminage des composites

Gaoudi soumia

Contribution à l'étude des céramiques réfractaires

Safer Hania , Bouzidi Hadjer

Contribution à l'étude des composites électroniques

SAFER Hania , Bouzidi Hadjer

Contribution à l'étude des céramiques électroniques

Guermit Mohamed Lamdjed , Bellah Youcef

CONTRIBUTION A L’ETUDE DES DÉFORMATIONS STRUCTURELLES DES MACHINES OUTILS

Bouteraa Seyf Eddine

Contribution au design d’un dispositif de retournement de chassis lors du soudage

Bouchareb el yamine , El Elmi Khalil

Investigations des microstructures d’acier soude a l’arc-application aux chassis aci de msila

Saadini Rachid , Mihoubi Khaled

Contribution à l’étude d’un palier hydrodynamiques lisse

ATALLAH Hamza , Mahroug Elwalhi

Contribution a l'etude des composites

Kechiche Fateh

Contribution à la Simulation de la flexion 3pts

Soufi Sami

Etude des méthodes de contrôle des machines-outils conventionnelles

Bouzidi khadidja

Contribution a l'etude du procede d'usinage par jet d'eau

Daif sihem

CONTRIBUTION A L’ETUDE METALLURGIQUE DU SOUDAGE CAS DES ACIERS

This paper aims to strengthen composites by treated and untreated date palm fibers (PDF), with sodium hydroxide (NaOH), for light applications. With 75% cellulose content and a density of 1.2 g/cm3, the palm fibers were exposed to a preparatory treatment with 1.5% NaOH for 24 h prior to integration into a polyester. Four polyester samples comprising 30% of palm fiber were manufactured. Additionally, the palm fiber interface was evaluated using scanning electron microscopy (SEM) and optical microscopy. The specimens underwent mechanical testing and it shows that tensile (18% increase in stress and 1.2% increase in Young’s modulus) and flexural properties (20% increase in strength and 10% increase in Young’s modulus) of treated composites as compared with untreated fibers. A MATLAB-based Artificial Neural Network (ANN) model was applied to estimate stress and strain at break as well as the Young’s modulus, based on three input characteristics: section, sample length, and chemical treatment. It was obtained that the polyester reinforced by NaOH-treated palm fibers increased the mechanical characteristics relative to the untreated fibers. The coefficient of determination R3 in the ANN models is 0.87. These results suggest that the ANN model is a useful tool for predicting mechanical properties.

Citation

Hocine MAKRI , , (2024-09-04), Investigation on the Mechanical Behavior of Date Palm Fibers Reinforced Composites: Predictive Modelling Using Artificial Neural Networks (ANNs), Journal of Natural Fibers, Vol:21, Issue:1, pages:17, Francis and Taylor

This research aims to examine the physical, structural and chemical properties of Aster Squamatus (AS) fibres, which are commonly found in Algeria, Brazil, France and the West Indies. In this work, we assess their appropriateness as reinforcing fillers to fabricate components for polymer composites principally designed for lightweight applications. To accomplish this objective, an extraction of fibres from plants modification of AS fibres and characterization of both untreated fibres (UASFs) and alkali-treated AS fibres (TASFs) are conducted. We analysed the crystallinity, chemical composition, thermal characteristics, and mechanical properties of AS fibres as per standard methods. It's clear from chemical treatment that amorphous components were successfully eliminated from the AS fibres, including hemicellulose, lignin, and wax. Consequently, the fibres' thermal, physical, and mechanical characteristics including Young's modulus, tensile strength, crystalline index, and surface roughness were substantially enhanced. It was determined that the fibres possessed a thermal stability of around 250 °C, with the maximal degradation temperature rising from 372.50 to 375.35 °C. The maximum stress rose from 183.24 ± 25.27 to 302.00 ± 24.91 MPa, the Young's modulus increased from 11.08 ± 1.1 to 18.53 ± 1.45 GPa, and the crystallinity index increased from 43% to 45%. Two-parameter Weibull statistics showed a strong link between experimental data and mechanical features of the twenty samples. We concluded from this work that AS plant fibres can serve as a robust reinforcing material in polymer composites for various applications. Keywords: Aster squamatus fibres; Composites; Alkali treatment; Morphological properties; Thermal properties; Tensile test; Weibull statistics

Citation

DJALAL Mebarkia , Hocine MAKRI , , (2024-08-20), Effect of alkali treatment on new lignocellulosic fibres from the stem of the Aster squamatus plant, Journal of Materials Research and Technology, Vol:32, Issue:, pages:2882-2890, Elsevier

This study assesses the impact of alkaline treatments and volume fractions on biocomposites composed of a high-density polyethylene (HDPE) matrix reinforced with date palm tree fibers (FPDS). Tensile tests were conducted on both untreated and NaOH-treated biocomposites. Additionally, fiber analysis was performed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results reveal higher strength and stiffness compared to HDPE, albeit with limited plasticity making the material brittle. The NaOH treatment enhances certain mechanical properties. Further assessments encompassed hardness, density, melt index, and Izod impact tests. Two volume fractions, 20% and 25%, of FPDS were tested. The study establishes a correlation between empirical predictions and artificial neural network (ANN) models. Notably, an ANN architecture consisting of two input factors, 10 hidden nodes, and one output provides the analysis of mechanical properties. This investigation highlights the potential of FPDS-reinforced HDPE biocomposites, emphasizing their mechanical performance under various treatments and fiber levels.

Citation

Hocine MAKRI , , (2024-04-10), Assessment of mechanical and physicochemical properties of palm fiber composites: Effect of alkaline treatment and volume alterations, Journal of Composite Materials, Vol:58, Issue:15, pages:1789-1800, Elsevier

Despite the many benefits that have expanded the field of fiber-reinforced composites applications, they remain vulnerable to failure by fold separation, a failure mode known as delamination. In some applications, fiber-reinforced composites come in the form of tubes for civil use in the underground transport of liquids. Usually these pipes are manufactured using a filament winding technique. Thus, an appropriate selection of the winding angle is therefore required to enhance the delamination resistance. In this paper, the effect of the winding angle and the initial crack length on the delamination behavior of vinyl ester resin-fiberglass composites was investigated experimentally. Accordingly, DCB samples with different winding angles (±45°, ±55° and ±65°) were cut from pipes of 08folds manufactured by the filament winding technique and then subjected to tests under mode-I loading. Previously, initial cracks of 50mm and 100mm length were created by the introduction of a thin film of polytetrafluoroethylene (PTFE) during the winding process. The mode-I fracture tests were conducted according to ASTM D5528-94a standards. Results show that the delamination resistance is enhanced with higher winding angles and lower initial crack lengths, respectively. The qualitative analysis shows that ±65° winding angle provides the best delamination resistance behavior compared to ±55° and ±45° winding angles

Citation

Hocine MAKRI , , (2023-12-14), Experimental investigation of the delamination behavior of glass-fibre reinforced composite pipes, U.P.B. Sci. Bull., Series D, Vol:85, Issue:4, pages:16, Politechnica University of Bucharest

In this paper, the effect of the winding angle and the number of folds on the delamination behavior of vinyl ester resin-fiberglass composites under mode-I loading was investigated experimentally. Accordingly, double cantilever beam samples with 8 and 12 folds and with different winding angles (±45°, ±55° and ±65°) were cut out of industrial pipes and subjected to mechanical tests. Furthermore, thick films were introduced during the winding process to create initial cracks of 50mm. The Mode-I fracture tests were conducted according to ASTM D5528-94a standards. Results show that the [±65°] winding angle provides the best delamination behavior and greater resistance to cracking compared to the [±55°] and [±45°] winding angles. Results also show that the number of folds has no effect on the initiation of the crack stage, but it significantly affects the propagation stage.

Citation

Hocine MAKRI , , (2023-10-23), Comprehensive study of the delamination of glass-fiber based composites., Academic Journal of Manufacturing Engineering, Vol:21, Issue:3, pages:8, Editura Politehnica

In this paper, the effect of the winding angle and the number of folds on the delamination behavior of vinyl ester resin-fiberglass composites under mode-I loading was investigated experimentally. Accordingly, double cantilever beam samples with 8 and 12 folds and with different winding angles (±45°, ±55° and ±65°) were cut out of industrial pipes and subjected to mechanical tests. Furthermore, thick films were introduced during the winding process to create initial cracks of 50mm. The Mode-I fracture tests were conducted according to ASTM D5528-94a standards. Results show that the [±65°] winding angle provides the best delamination behavior and greater resistance to cracking compared to the [±55°] and [±45°] winding angles. Results also show that the number of folds has no effect on the initiation of the crack stage, but it significantly affects the propagation stage.

Citation

Mohamed SLAMANI , Hocine MAKRI , SELMA Baali , , (2023-10-01), COMPREHENSIVE STUDY OF THE DELAMINATION OF GLASS-FIBER BASED COMPOSITES, ACADEMIC JOURNAL OF MANUFACTURING ENGINEERING, Vol:21, Issue:3, pages:61-68, ACADEMIC JOURNAL OF MANUFACTURING ENGINEERING

During welding operation, a thermal phenomenon related to the repeated process of non-uniform heating followed by cooling at room temperature. As a result, the microstructure of the weld bead and surrounding areas of the base metal are modified and are partially affected by the poorly heated area during welding. The object of this work concerns the microstructural and mechanical characterization of a welded joint with wire type SG2 carried out on micro alloyed ferritic base steel with low carbon (0.45% C). This commercial product is widely used in mechanical engineering in the machinery industry, cranes. Samples were cut from rough as hot-rolled sheet. A chemical analysis of the base metal was conducted to confirm the chemical composition previously provided. Mechanical polishing and chemical attack with Nital 3% followed by microstructural characterization by optical microscopy of the welds followed by micro hardness tests using an instrumented microdurometer. The results obtained make it possible to draw the following conclusions: In the bonding area where the thermal input is quite large and short, a grain size gradient was obtained, conditioned by the temperature gradient of the welding along the plates. In the melting zone, different structures are found conditioned by the cooling rate; for the large cooling rates, in the case of external passes: a characteristic needle structure of the out of equilibrium ferrite has been revealed. For passes heated several times, in the case of regenerated areas of the lower part of the weld joint; a ferritic structure of weidmanstatten with increasingly regular grains and for the internal passes of the intermediate part having undergone heating treatments; structures closer to the equilibrium state or to mixed textures of regular ferrite, due to the coalescence of ferrite needles. These results confirm the modification of the initial microstructure by thermal input during welding.

Citation

Hocine MAKRI , ,(2023-09-26), Microstructure investigation on low carbon steel joints arc welded,3rd International Conference on Innovative Academic Studies ICIAS 2023,TURKEY

The aim of this investigation is to evaluate the use of new lignocellulosic fiber extracted from Centaurea hyalolepis plant as a potential reinforcement for light-weight composite applications. In this study, anatomical structure and morphological surface of Centaurea hyalolepis fiber were conducted. The physical-chemical, thermal, crystalline,mechanical, characteristics of extracted fibers were also examined using Attenuated Total Reflectance-Fourier Transform Infrared (ATRFTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and tensile test. ATR-FTIR analysis confirmed the existence of the main components of lignocellulosic fiber (lignin, cellulose, and hemicellulose). XRD revealed the presence of cellulose with a crystallinity index of 57.93%.By densimetry, the density of Centaurea hyalolepis was determined as 1.13 g/cm3. The Centaurea hyalolepis was found to be thermally stable up to 271°C. The kinetic activation energy was determined as 115.943 kJ/mol. Tensile tests revealed that the mean tensile strength and Young’s modulus of Centaurea hyalolepis fiber were about 372,5 MPa and 9.036 GPa respectively. Because of the dispersion in the experimental tensile results, the Weibull statistical analysis with two parameters was carried out. Regard these findings, the Centaurea hyalolepis fibers can be a suitable candidate for low density polymeric composites reinforcement.

Citation

Hocine MAKRI , , (2023), Extraction and characterization of novel lignocellulosic fibers from Centaurea hyalolepis plant as a potential reinforcement for composite materials, Journal of Composite Materials, Vol:57, Issue:21, pages:14, SAGE

The objective of the present work is to determine the mechanical properties of ceramic composites on the basis of load-discharge curves and crack-length measurements. For the purpose, ceramic composite samples were prepared from different mixtures of starting powders of boehmite (AlOOH) and zircon (ZrSiO4) by variation of the Boehmite to zircon weight ratios and then subjected to a reactive sintering in air at 1600°C. The sintered samples were characterized in terms of phase composition, relative density, microstructures and mechanical properties by Vickers indentation tests. Furthermore, the microstructure was related to mechanical properties. The effects of both initial powder ratios and sintering conditions on the hardness and fracture toughness were analyzed. The results showed the possibility to manufacture a ceramic material with desired phases, acceptable density and mechanical properties by varying the composition of the initial powders. The results also show that the increase in zirconia rate improves toughness but promotes the porosity which acts on the opposite of toughness and hardness but enhances elasticity. The use of load-unload curves for the determination of mechanical properties of ceramic materials is effective.

Citation

Hocine MAKRI , ,(2022), Determination of mechanical properties of Alumina-Zirconia ceramic composites by instrumented indentations,3rdInternational Conference on Applied Engineering and Natural Sciences. ICEAENS2022. July 20-23, 2022, Konya, Turkey,Konya, Turkey

Fibre-reinforced polymer composites have replaced many conventional materials, especially in liquid transport applications because of some of the advantages they offer. But when loaded, these materials present damage in the form of layer separation. This mode of degradation is known as delamination. The main objective of this experimental work is to study this behavior in Mode-I type loading, focusing the influence of the winding angle and the initial crack on the GIC interlaminar toughness for the case of composite material elements taken from tubes with transverse curvature. For the experimental, DCB samples are tailored in 500mm-radius tubes of fibreglass vinyl ester resin based composite obtained by filament winding at different winding angles (45°, 55° and 65°) and having initial crack a0 of different length 50mm, and 100mm. A thin film of PTFE is interposed in the middle layer during the construction of the tubes as a crack initiator. Special loading devices were prepared and used to conduct the fracture tests in Mode-I in accordance with ASTM D5528-94a. The tests were performed on an INSTRON-5969 machine. The results obtained showed that the shorter the initial cracks, the greater the toughness of the interlaminar fracture, achieving an inverse relationship between the interlaminar fracture toughness and the length of the initial crack. The results also showed that the 65° winding angle confers a good behavior vis-à-vis delamination as the 55° and 45° angles.

Citation

Hocine MAKRI , ,(2022), Effect of winding angle and initial crack length on delamination in fiber reinforced composite tubes,1st International Conference on Innovative Academic Studies. ICIAS2022. September 10 - 13, 2022, Konya, Turkey,Turkey

The mechanical properties of steel are part of the necessary conditions to know for the proper functioning of mechanical systems in industry. The objective of this work is the study of the mechanical characteristics of low alloy steel AISI 4041. Considering an experimental approach based on the influence of different heat treatments (quenching and tempering at different temperatures) on the behavior of the steel studied in tension. The desired mechanical characteristics relate to hardness, breaking strength, elongation and the coefficient of necking. After the tensile tests, it was observed that there is a reciprocity between the tempering temperature on the one hand and the hardness of the material and the breaking strength on the other hand. A certain proportionality noticed between the hardness, the elongation and the coefficient of necking.

Citation

Abdelmalek ELHADI , Hocine MAKRI , ,(2022), Study of the Influence of Tempering Temperature on the Tensile Behavior of a Low Alloy Steel,2nd International Conference on Engineering and Applied Natural Sciences,Turkey

In order to understand the mechanical behavior in tension of the aluminum alloy 6082, we carried out an experimental study. After the samples (tensile specimens) were manufactured on the lathe according to the standardized dimensions, they were heat-treated (solution treatment, water quenching and tempered at different temperatures to have different hardness. Tensile tests were carried out by the tensile machine, which allowed us to have experimental results and to understand the behavior of the aluminum alloy 6082 through its mechanical properties such as hardness, breaking strength, elongation and coefficient of necking.

Citation

Abdelmalek ELHADI , Hocine MAKRI , ,(2022), Effect of Heat Treatment of Mechanical Tensile Characteristics of an Aluminum Alloy,2nd International Conference on Engineering and Applied Natural Sciences,Turkey

This work presents a study of the determination of the temperature at the interface in the dry friction of the low alloy steel pin against a medium-hard carbon steel disk. The parameters: Normal load applied, sliding speed, hardness of the material and coefficient of friction resulting during the tribological tests carried out play a very important role on the thermal effects of the opposing surfaces. The Archard model was used to determine the temperature at the tribological couple interface, using the parameters mentioned above.

Citation

Abdelmalek ELHADI , Hocine MAKRI , Mohamed SLAMANI , ,(2022), Evaluation of Temperature at the Interface of Pairs of Steels in Dry Sliding as a function of Hardness,1st International Conference on Scientific and Academic Research,Turkey

Les composites multicouches en polymères renforcés de fibre de verre ont remplacé beaucoup de matériaux conventionnels dans les applications de transport de liquides à cause de certains avantages qu’elles offrent. Mais, lorsqu’ils sont chargés, ces matériaux sont vulnérables aux dommages menant à la séparation des couches. Ce mode de dégradation est connu sous le nom de délaminage. L’objectif principal de ce travail expérimental est d'étudier le comportement vis-à-vis du délaminage en Mode-I pour des éléments en matériaux composites présentant un rayon de courbure et qui sont prélevés de tubes. Focalisant l’influence de l'angle d'enroulement et la fissure initiale sur la ténacité interlaminaire GIC. Pour atteindre cet objectif, des échantillons DCB présentant a courbure sont réalisés à partir de tubes composites de 500mm de rayon fabriqués à partir de résine de vinyle ester et renforcé en fibre de verre élaborés par enroulement filamentaire selon différents angles d'enroulement (±45°, ±55° et ±65°) et comportant fissure initiale a0 de longueur différentes 50, et 100mm. Les pré-fissures sont réalisés par interposions d’un film mince de PTFE dans la couche médiane lors de l’élaboration des tubes. Des dispositifs de chargement spéciaux conformes aux normes ASTM D5528-94a ont été préparés et utilisés pour mener les essais mécaniques de rupture en mode-I. Les essais ont été réalisés sur une machine INSTRON-5969. Les résultats obtenus ont montré une relation inverse entre les valeurs de ténacité de la rupture interlaminaire et la longueur de la fissure c’est à dire, moins long sont les longueurs des pré-fissures plus grands sont les valeurs de la ténacité de la rupture interlaminaire et que l'angle d'enroulement ± 65° confère au matériau un bon comportement vis-à-vis du délaminage que les angles ± 55° et ± 45°.

Citation

Hocine MAKRI , ,(2021), ETUDE DU DÉLAMINAGE DANS LES TUBES EN MATÉRIAUX COMPOSITES,ETUDE DU DÉLAMINAGE DANS LES TUBES EN MATÉRIAUX COMPOSITES,oran

Les composites multicouches en polymères renforcés de fibre de verre ont remplacé beaucoup de matériaux conventionnels dans les applications de transport de liquides à cause de certains avantages qu’elles offrent. Mais, lorsqu’ils sont chargés, ces matériaux sont vulnérables aux dommages menant à la séparation des couches. Ce mode de dégradation est connu sous le nom de délaminage. L’objectif principal de ce travail expérimental est d'étudier le comportement vis-à-vis du délaminage en Mode-I pour des éléments en matériaux composites présentant un rayon de courbure et qui sont prélevés de tubes. Focalisant l’influence de l'angle d'enroulement et la fissure initiale sur la ténacité interlaminaire GIC. Pour atteindre cet objectif, des échantillons DCB présentant a courbure sont réalisés à partir de tubes composites de 500mm de rayon fabriqués à partir de résine de vinyle ester et renforcé en fibre de verre élaborés par enroulement filamentaire selon différents angles d'enroulement (±45°, ±55° et ±65°) et comportant fissure initiale a0 de longueur différentes 50, et 100mm. Les pré-fissures sont réalisés par interposions d’un film mince de PTFE dans la couche médiane lors de l’élaboration des tubes. Des dispositifs de chargement spéciaux conformes aux normes ASTM D5528-94a ont été préparés et utilisés pour mener les essais mécaniques de rupture en mode-I. Les essais ont été réalisés sur une machine INSTRON-5969. Les résultats obtenus ont montré une relation inverse entre les valeurs de ténacité de la rupture interlaminaire et la longueur de la fissure c’est à dire, moins long sont les longueurs des pré-fissures plus grands sont les valeurs de la ténacité de la rupture interlaminaire et que l'angle d'enroulement ± 65° confère au matériau un bon comportement vis-à-vis du délaminage que les angles ± 55° et ± 45°.

Citation

Hocine MAKRI , Hocine MAKRI , ,(2021), Etude du délaminage dans les tubes en matériaux composites,2. Séminaire international sur l’Industrie et la Technologie.12 et 13 Mars 2021.,Oran. Algeria

Les composites multicouches en polymères renforcés de fibre de verre ont remplacé beaucoup de matériaux conventionnels dans les applications de transport de liquides à cause de certains avantages qu’elles offrent. Mais, lorsqu’ils sont chargés, ces matériaux sont vulnérables aux dommages menant à la séparation des couches. Ce mode de dégradation est connu sous le nom de délaminage. L’objectif principal de ce travail expérimental est d'étudier le comportement vis-à-vis du délaminage en Mode-I pour des éléments en matériaux composites présentant un rayon de courbure et qui sont prélevés de tubes. Focalisant l’influence de l'angle d'enroulement et la fissure initiale sur la ténacité interlaminaire GIC. Pour atteindre cet objectif, des échantillons DCB présentant a courbure sont réalisés à partir de tubes composites de 500mm de rayon fabriqués à partir de résine de vinyle ester et renforcé en fibre de verre élaborés par enroulement filamentaire selon différents angles d'enroulement (±45°, ±55° et ±65°) et comportant fissure initiale a0 de longueur différentes 50, et 100mm. Les pré-fissures sont réalisés par interposions d’un film mince de PTFE dans la couche médiane lors de l’élaboration des tubes. Des dispositifs de chargement spéciaux conformes aux normes ASTM D5528-94a ont été préparés et utilisés pour mener les essais mécaniques de rupture en mode-I. Les essais ont été réalisés sur une machine INSTRON-5969. Les résultats obtenus ont montré une relation inverse entre les valeurs de ténacité de la rupture interlaminaire et la longueur de la fissure c’est à dire, moins long sont les longueurs des pré-fissures plus grands sont les valeurs de la ténacité de la rupture interlaminaire et que l'angle d'enroulement ± 65° confère au matériau un bon comportement vis-à-vis du délaminage que les angles ± 55° et ± 45°.

Citation

Hocine MAKRI , Hocine MAKRI , ,(2021), Etude du délaminage dans les tubes en matériaux composites,2. Séminaire international sur l’Industrie et la Technologie.12 et 13 Mars 2021.,Oran. Algeria

During multipass welding, cumulative and repetitive thermal phenomena may lead to development of cracks that can seriously compromise the quality of the welded joint. The use of Non-Destructive Testing methods is needed for the in-service inspection of the welded joint quality. To reliably evaluate the performance of an NDT procedure for in-service inspections, different types of artificial defects are used for this study. They have to be representative enough in comparison with the real service defects. For instance, thermal crack was realistically created by machining in a welded joint achieved by MAG welding deposition of melted SG3 wire on E36-3 steel, this case study being widely met in the crane industry. The approach consists of comparing two different ultrasonic techniques (Normal beam inspection and Angle beam inspection) in order to evaluate their performance in detecting and determining the size of well-known defects. Despite the difficulty in developing and interpreting the on-screen signals, caused by uncertainty in measuring the defect size, better results have been achieved when the angle beam inspection technique has been applied for the in-service inspections.

Citation

Hocine MAKRI , , (2019), EXPERIMENTAL INVESTIGATIONS TO EVALUATE THE VALIDITY AND PERFORMANCE OF NDT PROCEDURES FOR IN-SERVICE INSPECTIONS, ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI, FASCICLE XII, Welding Equipment and Technology, Vol:30, Issue:1, pages:59-66, Galati University Press

Several phenomena occurring simultaneously in the welding operation, the thermal phenomenon related to the repeated non-uniform heating process followed by cooling at room temperature, affect the weld bead enormously and microstructurally modify the heat affected zone and its vicinity of the basic metal. The aim of this work concerns the microstructural and mechanical characterization of a SG2 alloy copper-welded joint made on a mainly micro-alloyed ferritic 0.54% carbon steel, widely used in construction in the gear industry, Cranes, samples were cut on a crude in the form of hot-rolled sheets provided by the Algerian company ACI-M'sila. A chemical analysis of the base metal to confirm the chemical composition was performed a microstructural characterization by optical microscopy of the welds were carried out followed by microhardness tests on an instrumented microdurometer. The results obtained make it possible to conclude that in the connection zone where the thermal input is brief and fairly important, a grain size gradient is encountered, so the grain size is conditioned by the gradient of the welding temperature along the sheets. Depending on the cooling rate in the melting zone, it can be seen that for the high cooling rate in the case of external passes, a needle structure characteristic of out-of-equilibrium ferrite is obtained. regenerating areas case of the lower part of the joint, a ferritic structure of weidmanstatten with grains more and more regular. For internal passes cases of the intermediate part having undergone reheating treatments, structures closer to the equilibrium state or to mixed textures of regular ferrite, due to the coalescence of the ferrite needles.

Citation

Hocine MAKRI , ,(2018), Caracterisation Microstructurale des Joints d’Acier 0.54% de Carbone Soudes a l’Arc.,International Seminar in Industrial Engineering and Applied Mathematics (ISIEAM'2018),Skikda-Algeria

The aim of the investigation was to find a liaison between materials chemicalcomposition, microstructure and mechanical properties for the E36-3 low alloy high strength steel, also called low alloy structural steel. The base material widely usedin fabrication of gear and cranes from the Algerian company CIG Constantine waswelded with cored wire SG3 by the Gas Metal Arc Welding (GMAW) technique. The behaviour of E36-3 steel in terms of metallurgical modifications, hardness and Charpy V-notch impact in weld metal (WM), heat affected zone (HAZ) and base metal (BM) was investigated and discussed. The experimental results highlighted theimpact of the welding process on the microstructure and mechanical properties. The effect of the thermal cycles developed during welding on the microstructure was reflected by the formation of various structures with various characteristics which,finally, have determined the mechanical properties of the welded joint. Besides, the influence of the number of passes on the fusion weld microstructure was studied. Inside the fusion weld, due to the effects produced by the repeated heating andcooling on the previous layers, a structure of pearlite and ferrite regenerated with fine grains was developed, while in the case of the outer passes, a combination of pearlite and acicular ferrite was obtained. The analysis of the fracture mechanismof the welded joints revealed the presence of ductile fracture, characterized bytearing of metal accompanied by appreciable global plastic deformation, at room temperature. A severe decrease of the plasticity properties of the joint was observed in the temperature range of (-20°C)...(-80°C).

Citation

Hocine MAKRI , , (2016), INVESTIGATION ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF E36-3 STEEL WELDED JOINT, Annals of “Dunarea de Jos” University, Fascicle XII, Welding Equipment and Technology, Vol:27, Issue:1, pages:47-54, Galati University

Low cost composite ceramics based on zircon-mullite-zirconia-alumina phases were prepared by reaction sintering of boehmite (AlOOH) and zircon (ZrSiO4) powders. Boehmite to zircon weight ratios of the starting powders were varied (10 to 90 wt. %). The green compacts were made by uniaxial pressing at 7 MPa followed by cold isostatic pressing at 250 MPa. A reactive sintering in air of these compacts was made at different temperatures between 1400° and 1600°C during 2 hours. A quantitative evaluation of the present phases was based on XRD. Dilatometric tests on the reaction-sintered composites were carried out in order to study the zirconia phase’s transformations and their thermal expansion coefficient (). In addition, the effects of both boehmite/zircon ratios and sintering conditions on the mechanical properties (Hardness Hv, Elastic modulus E and fracture toughness KIC) of the obtained composites were characterized by Vickers indentation.

Citation

Hocine MAKRI , , (2015), Zirconia transformation in multi-phases ceramic composites, Journal of The Australian Ceramic Society, Vol:51, Issue:1, pages:60 – 72, Australian Ceramic Society

In this work, different composites (zircon–mullite–zirconia, mullite–zircon–zirconia, mullite–zirconia, mullite– zirconia–alumina and alumina–mullite–zirconia) were developed by reaction sintering of boehmite (AlOOH) and zircon (ZrSiO4). Several mixtures were used by varying the boehmite content from 10 to 90 wt. %. All powders were mixed and grounded by ball milling and then pressed in cylindrical form. Finally, the green specimens were sintered under normal conditions for 2 hours at temperatures between 1400 and 1600°C, with a heating rate of 5°C/min. The dilatometric curves reveal several microstructural transformations in these mixtures. The X-rays diffraction spectra revealed factors such as percentage of boehmite and zircon and the sintering temperature lead to the formation of several composites. The presence of the various phases was confirmed by micrographic observations.

Citation

Hocine BELHOUCHET , Hocine MAKRI , , (2014), Elaboration and characterization of multiphase composites obtained by reaction sintering of boehmite and zircon, Journal of the Australian Ceramic Society, Vol:50, Issue:2, pages:135 – 146, Australian Ceramic Society