Browsing by Author "Gaceb, M."
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Item Analysis of crack evaluation standards in welded joints of pipelines(Elsevier, 2005) Bouzid, R.; Bouali, E.; Gaceb, M.Item Approche probabiliste au contrôle et suivi des joints de soudure des conduites(2007) Abdelbaki, Noureddine; Bouali, E.; Bouzid, R.; Gaceb, M.Les conduites de transport des hydrocarbures sont des constructions mécano-soudées, confrontées en exploitation à des conditions particulières de fonctionnement. Les ruptures des joints de soudure des conduites, bien que rares, ont des conséquences majeures aux niveaux humain, environnemental et économique. Ces derniers sont le siège de formation des fissures de fatigue. L'utilisation des résultats d'inspection in situ, à partir des techniques de contrôle non destructif, est une composante essentielle de la réévaluation et du maintien de l'intégrité des conduites dans leur fonction. Elle nécessite des méthodes de calcul et des outils d'aide à la décision en appui des campagnes d'inspection et de réparation. C'est dans ce contexte que la présente étude a été réalisée qui est une contribution à l'effort méthodologique d'évaluation de l'endommagement par détection de fissure et d'estimation de la durée de vie résiduelle des joints de soudure sous sollicitations en fatigueItem Establishment of data base and a classification of defects in the metal of pipes according to their severity(Elsevier, 2012) Bettayeb, M.; Bouali, E.; Abdelbaki, Noureddine; Gaceb, M.Given the distances between areas of production and consumption of hydrocarbons, transport by pipeline is the most competitive means. These pipelines made of metal pipes can contain several types of defects of different origins. These defects can lead to pipeline failures that may have serious consequences resulting in ecological or financial disasters. The causes of these failures can be of various kinds. To assess the integrity and study the ageing of hydrocarbons transport pipelines is a current problem in the world which must be solved. The degraded state of thousands of kilometers of pipeline in the world requires the elaboration of rehabilitation by repair or replacement programs of sections in poor condition. If on one hand rehabilitation operations do improve the safety of hydrocarbons transport pipelines and prolong their remaining life, they are very expensive on the other. Therefore they must be carried out according to a previously well established plan, which determines the priority given. This priority must be defined by a multi-criteria evaluation, which also includes the criterion of severity of the defects located in the pipes metal according to the result of previous inspections of the pipelines towards the importance and the integrity of each section of the pipe.In this context the elaboration of a database and a classification of the defects in the metal of the hydrocarbons transportation pipes according to their severity are essential in this studyItem Etude de l’influence de l’état de surface sur la tenue à la fatigue d’un acier XC48(2008) Gaceb, M.; Brahimi, S.On parle communément de la durabilité d'un matériau comme s'il s'agissait d'une propriété fondamentale définie comme la période de temps pendant laquelle le matériau accomplira une fonction utile. La vie utile d'un matériau en service dépend cependant toujours non seulement de la combinaison des facteurs de charge et d'environnement auxquels il est soumis mais aussi des facteurs d'intégrité dont l'état de surface constitue un facteur très important, et c'est ainsi qu'il faut toujours tenir compte des paramètres d'état des surfaces dès la mise en service lorsque l'on considère la durabilité, ou vie du matériau en service. Cette dépendance est encore plus ressentie dans le cas des matériaux utilisés dans la confection de composants sollicités à la fatigue. Que ce soit en fatigue mécanique ou en fatigue de contact, les gradients de propriété au voisinage de la surface (microstructure, écrouissage, contraintes résiduelles) et les imperfections superficielles apportées par les procèdes de fabrication jouent un rôle primordial sur la tenue à la fatigue en service du composant. La présente étude vise à établir l'influence des paramètres de surfaces réalisées par tournage sur la résistance à la fatigue d'un acier XC 48, en s'attachant plus particulièrement a identifier l'effet de la rugosité qui peut être produite sous différentes conditions d'usinage des surfaces. Pour ce faire, diverses éprouvettes, présentant des combinaisons variées d'état de surfaces, réalisées par tournage à différents paramètres de coupe ont été soumises à des essais de flexion rotative et l'effet sur la durée de vie et la limite de fatigue, pour divers conditions de chargement, a été évaluéItem Influence of properties of large pipes on the reliability of pipelines(2008) Abdelbaki, Noureddine; Bouali, E.; Gaceb, M.; Bouzid, R.Item Investigation of the effect of aluminum alloy position on residual stresses in dissimilar fsw weld by using the ultrasonic method(IOP Publishing, 2018) Hadji, Idir; Badji, Riad; Gaceb, M.; Kherrouba, N.; Rabahi, L.The main goal of this study is to show the effect of the advancing side (AD) and the retreating side (RT) position on the Residual stresses and local mechanical behaviour of dissimilar friction stir welds of aluminum alloys AA2024-T3 and AA7075-T6. Different samples were produced by varying the rotational speed of the tool (1200 and 1400 rpm) and the alloy position regarding the advancing side of the tool. Ultrasonic Method has been used to evaluate Residual Stresses. This method is based on the acoustoelastic effect, which measures the velocity variation of the elastic waves according to the stress state of the material. This can be achieved through a calibration test, which permits the determination of the acoustoelastic coefficient (K). The results show a tensile stress in the Nugget (N), the heat affected zone (HAZ) and a compression stress in the base metal (BM). Increasing the rotational speed reduces the amplitude of the longitudinal residual stresses with a high reduction in the case where AA7075 - T6 is in the advancing side whit 1400 rpm. This has been directly associated to the increase in the heat input and the reduction of the thermal mismatch between different areas of the weld. The microstructure effect of aluminum alloy position acts on the acoustoelastic constant K. The choice of t0 corrects the overestimated residual stresses in the (HAZ) and (N).Item Microstructure and mechanical behavior in dissimilar 13Cr/2205 stainless steel welded pipes(Elsevier, 2015) Bettahar, K.; Bouabdallah, Mounira; Badji, R.; Gaceb, M.; Kahloun, C.; Bacroix, B.Thiswork aims to investigate the microstructure and themechanical behavior of dissimilar 13Cr Supermartensitic/2205 Duplex stainless steelwelded pipes. A wide variety ofmicrostructures resulting fromboth solidification and solid state transformation is induced by the fusion welding process across the weld joint. The tensile tests show that the deformation process of the dissimilarweld joint ismainly controlled by the two basematerials: the duplex steel at the beginning of the deformation and the supermartensitic one at its end. This is confirmed by the microtensile tests showing the overmatching effect of the weld metal. The fatigue tests conducted on dissimilar welded specimens led us to conclude that the weld metal is considered as a weak link of the weld joint in the high cycle fatigue regime. This is supported by its lower fatigue limit compared to the two basematerials that exhibit a similar fatigue behaviorItem Parametric study of the mechanical properties of nanocrystalline TiN/CrN multilayer coatings with a special focus on the effect of coating thickness and substrate roughness(Elsevier, 2021) Atmani, Taous Doria; Gaceb, M.; Aknouche, Hamid; Nouveau, C.; Bouamrene, M.S.In a plot to improve the performance of steel mechanical parts subject to aggressive friction solicitations, three batches of deposits of TiN and CrN layers on steel substrates with two different roughnesses have been obtained using reactive DC magnetron sputtering. The present study was conducted to determine the effect of varying TiN/CrN multilayer coatings thickness (varying modulated period Λ and interlayer thickness), on their mechanical and tribological properties. The morphological and the structural properties were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The nanoindentation measurements displayed improvement in hardness (> 40 GPa) and Young's modulus (> 600 GPa) for the coating with Λ ≅ 12 nm (TiN Λ/2 ≅ 7.5 nm + CrN Λ/2 ≅ 4.5 nm) thickness and the higher number (300) of interfaces, deposited on the rougher substrate. Its low coating damage under the scratch test, associated with its estimated adhesion work (Wad), indicated a good cohesive/adhesive strength and improved structural and mechanical propertiesItem Reliability of an unstable pipeline used for natural gas transportation(2007) Abdelbaki, Noureddine; Bouali, E.; Bouzid, R.; Gaceb, M.Item Semi-probabiliste approach of hydrocarbons canalization(2007) Abdelbaki, Noureddine; Bouali, E.; Bouzid, R.; Gaceb, M.Item Study of defect admissibility in gas pipelines based on fracture mechanics(School of Engineering, Taylor’s University College, 2009) Abdelbaki, Noureddine; Bouali, E.; Gaceb, M.; Bettayeb, M.Bearing in mind the considerable distances between natural gas fields and consumers’ appliances, transport by gas pipelines remains the most competitive means. These gas pipelines which are generally made of steel pipes may contain however several types of defects of various origins and which are susceptible to initiate cracks which may grow under some circumstances to such extent as to lead to fracture. Failures of gas pipelines may have serious consequences and may lead to catastrophes from ecological and financial viewpoints. It is therefore interesting to study the defect admissibility so as to maximize safety and minimize exploitation costs through a simplified method based on the Failure Assessment Diagram (FAD). The latter is used in conjunction with Finite Element Analysis (FEM) applied to fracture mechanics to help decision making as to whether a given defect present in a pipe is acceptable or notItem Study of life and mechanical properties of welded joints of big diameter pipelines(2005) Abdelbaki, Noureddine; Fenineche, N.; Bouali, E.; Bouzid, R.; Gaceb, M.The increase in transportation capacities of pipe-lines necessitates the introduction of new construction tubes and new production technologies. Tubes should be produced according to pipe-lines service parameters. It is therefore useful to produce tubes which vary in diameter, in construction and mainly in the type of steel used for their production. For pipe of great diameter, destined to support high pressure, we use welded tubes made of controlled rolled steel and low alloyed improved steel. Tubes are the main constituents of pipe-lines. Their quality, the properties of their material and their welded joints determine to a high degree the possible deficiencies, stoppages and failures of pipe-lines. This is the reason why it is important to determine the requirements on tube steel and welded joints in terms of the service parameters of pipe-lines in order to avoid their rupture. The welded joints of tubes are subjected to complex static and dynamic loading, which takes place during pipe transportation, and during realization and exploitation of pipelines. The welding process of big diameter pipes is characterized by a great volume of melted metal and a large heat affected zone of the parent metal. The temperature in the vicinity of the weld joints varies from the melting temperature at the joint to lower temperatures in adjacent zones. In the region of the parent metal subjected to this temperature variation important alterations in the structure and in properties of the material take place. This is why it is estimated important to study this zone in which there is a reduction in the plasticity and the resilience of the metal and consequently there will be an increase in the probability of crack formation. The creation of a mechanical non-homogeneity in this zone reduces the work capacity of the weld joints and the reliability of pipe-lines reduces. It is in this context that the paper presented includes two parts: The first part is concerned with the hardness distribution and the resilience variation as a function of the temperature distribution in the heat affected zone of pipe. The second part considers the influence of the weld joint shape and the loading regime of the pipe-lines on their weld joints life in the big diameter pipes. This work shows how the bearing capacity of the weld joints wary with the mechanical non-homogeneity of weld properties and quality with their weld shape and with the relative thickness of the diameter layer in the welding. On the other hand this study shows the resilience variations in weld joints and in the parent metal of the pipes in the as bought state and after their mechanical ageing. The stress and strain concentration resulting from irrational configuration of welded joints cause the strength of weld subjected to cyclic loading to be diminished. This has lead to finish this work by the determination of the life specimens taken from weld joints in tubes and subjected to cyclic loads during testingItem A technique for identifying and characterizing the microcracks produced in machined surfaces(2007) Gaceb, M.; Gillibrand, D.Microcrack formation constitutes an mportant feature of the machining process and a undamental component of the surface integrity of machined components. Microcracks have been observed inside the shear zone and their presence used to explain some aspects of the chip formation process. A preliminary investigation conducted on a number of materials machined under various cutting conditions has confirmed microcrack formation on machined surfaces as a result of machining. There has been, however, no systematic study of these microcracks and their extent, dimensions and the conditions in which they are produced are not well known yet. Bearing in mind that surface microcracks can affect the fatigue, corrosion and other properties of machined components, it is important to devise some means of quantifying this microcrack formation. A technique of microcrack identification and measurement based on Transmission Electron Microscopy (TEM) is described in this paper along with its application. Two new parameters, namely the Microcrack Area Ratio (MAR) and the Microcrack Density (MD) are introduced and defined. The extent of microcrack formation on the surface of three different materials machined in the same cutting conditions is examined in the light of this technique. The results show that this technique seems promising and may be adopted in future investigations of microcrack formation on machined surfaces and the factors of influenceItem W-Ti-N thin film tribological behaviour for piston skirt properties improvement(Taylor & Francis, 2020) Chemaa, Khaled; Hassani, S.; Gaceb, M.; Madaoui, N.; Guebli, A.Tungsten-Titanium-Nitrogen (W-Ti-N) thin film, 1.1 μm in thickness, was deposited on Aluminium-Silicon (Al–Si) and stainless steel substrates using the Physical Vapour Deposition (PVD) sputtering system in order to study a new way to improve the tribological properties on engines piston skirts. Tribological test results showed very interesting friction coefficient and wear rates compared to uncoated piston skirt samples. The average value of the friction coefficient was approximately six times lower than that of the uncoated piston skirt samples. Wear rate was considerably lower. In addition W-Ti-N showed interesting corrosion behaviourItem Welded Joints in canalisations subjected to dynamic loads(Ed. Elsevier, 2005) Gaceb, M.; Bouali, E.; Bouzid, R.