Génie mécanique

Nombre total de résultats : 207
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Characterizations of joints HDPE welded by FSW

LATEF M, ZAHLOUL H, BADIDI BOUDA A, MEBTOUCHE A, ABBASE A  (2018)
Article de conférence

The aim of this work is the characterization of high density polyethylene (HDPE) joints welded by the Friction Stir Welding (FSW) technique. The characterization is done by destructive testing (mechanical tensile tests) for welded joints.To do this work, a series of experimental tests were made by taking in account of several parameters: - the geometry of the welding tool (pin), the axial force Fz applied to the tool along its axis of rotation, to compensate for the pressure formed in the weld zone, the speed of rotation of the tool, the speed of advance of the tool,in this work, we only take in account of the last two parameters.The results obtained were satisfactory and show the influence of these parameters on the quality of the joint. Voir les détails

Mots clés : FSW, HDPE, polymers, welding

Étude de l’influence des traitements thermiques sur les paramètresultrasonore : Application à la caractérisation non destructive des matériaux

Mohamed LATEF (En préparation)
Thèse de doctorat

L’efficacité des ultrasons dans le domaine de la caractérisation non destructive desmatériaux a été largement prouvée. Leur domaine d’application s’étend et sediversifie de jour en jour. Ils représentent un outil de choix pour la détermination del’état de contrainte de certains éléments dans les assemblages industriels. En effet, laprésence de contraintes mécaniques et/ou traitement thermique dans une structureinflue directement sur les paramètres de propagation des ultrasons dans lesmatériaux. L'analyse ultrasonore des matériaux est basée sur un principe simple de laphysique : le mouvement de n'importe quelle onde sera affecté par le milieu danslequel elle se propage. Ainsi, des changements d'un ou plusieurs des quatreparamètres facilement mesurables (temps de transit, atténuation, diffusion et spectredes fréquences) associés au passage d'une onde de haute fréquence à travers lematériau peuvent souvent être corrélés avec des changements des propriétésphysiques telles que la dureté, le module élastique, la densité, l’homogénéité, ou lastructure du grain. L’objet de ce travail porte sur l’étude de l’influence des traitements thermiques desmatériaux sur certains paramètres ultrasonores tels que la vitesse de propagation, lecoefficient d’atténuation et le décalage en fréquence de certains modes depropagation.L’objectif est mettre au point une technique non destructive pour remettre auxcaractéristiques d’un matériau par les mesures expérimentales d’un ou plusieursparamètres ultrasonores. Voir les détails

Mots clés : cnd, traitement thermique, vitesses de propagation, coefficients d’atténuation, décalages en fréquence

PRISE EN COMPTE DE L’ASPECT NON LINÉAIRE DANS L’ANALYSE MODALE DES STRUCTURES MÉCANIQUES

LATEF Mohamed, A?AD Abedelkarime  (2016)
Article de conférence

La connaissance des caractéristiques modales est primordiale dans l’étude du comportement dynamique des structures. L’application de l’analyse modale a été souvent réservée au domaine linéaire. Cependant, la plupart des structures mécaniques, rencontrées dans la pratique, présentent un comportement plus ou moins non linéaire. L’aspect non linéaire est d’origines diverses, dépend de plusieurs facteurs et peut se manifester globalement (géométrie, propriétés mécaniques,…) ou localement (conditions aux limites, joints, …).Dans ce travail, nous avons applique l’analyse modale a des systèmes vibratoires discrets (masse-ressort) non linéaires d’aspect géométrique.Plusieurs méthodes ont été utilisées pour déterminer les paramètres modaux, a savoir :- Balance harmonique (analytique).- Variété de l’invariant de Shaw-Pierre (numérique).- Range Kutta d’ordre 4.Des programmes ont été établis sous matlab pour exploiter ces méthodes. Les résultats obtenus nous ont permis de préciser :- la limite entre les systèmes linéaires et non linéaires.- l’effet des conditions initiales et le paramètre non linéaire.- domaine d’application des méthodes permettant l’étude des systèmes non linéaires. Voir les détails

Mots clés : analyse modal, Non linéarité, vibration, Paramètres modaux (Fréquences et Modes propres)

A Simple Isoparametric Finite Element Based on the Reddy’s Theory for the Laminated Plates Bending Analysis

K. BELKAID, B. BOUBIR, A. Guenanou, H. Aouaichia  (2018)
Article de conférence

The aim of this work is to develop a quadrilateral finite element based on Reddy’s third order shear deformation theory for the bending behavior analysis of composite laminated plates. The element is a C0 four-nodded isoparametric with seven degrees of freedom at each node, three translation components, two rotations and two higher order rotational degrees. In particular, selective numerical integration is introduced in order to improve the results and to alleviate the locking phenomenon. The performance and reliability of the proposed formulation are demonstrated by comparing the author’s results with those obtained using the three-dimensional elasticity theory, analytical solutions and other advanced finite element models. Voir les détails

Mots clés : Ajout mot cléThird Order Shear Deformation Theory, Ajout mot cléLaminated Composite Plates, Ajout mot cléFinite Element, Bending Behavior

Correlation between defect depth and defect length through a reliability index when evaluating of the remaining life of steel pipeline under corrosion and crack defects.

Djamel Zelmati, Oualid GHELLOUDJ, Abdelaziz AMIRAT  (2017)
Publication

Despite the various engineering models existing for lifetime investigation of hydrocarbon steel pipelines under localized corrosion and crack defects there is still a lack of information about the correlation between the two main parameters characterizing the geometrical defect model, depth and length. So the aim of the present work is a contribution in evaluating the remaining life of the pipeline using reliability analysis in order to correlate the two parameters through one common parameter, the reliability index. As a first step, the investigation is carried out on four standard and well established engineering models; Irwin, SINTAP, ASME B31G and Modified ASME B31G methods, aiming to coordinate results given by each of the four models. The potential defect depth and length correlation through a reliability index can be used as a decision-making tool to give realistic answers for replacing and/or repairing a tube subjected to internal pressure and on which flaws of different depths and lengths have been detected from inspection of a pipeline after few years of service. Voir les détails

Mots clés : corrosion, Defect, Reliability, Correlation, Sensitivity

Reliability estimation of pressurized API 5L X70 pipeline steel under longitudinal elliptical corrosion defect.

Djamel Zelmati, Oualid GHELLOUDJ, Abdelaziz AMIRAT  (2017)
Publication

The probabilistic approach is the best way to give realistic answers for design and maintenance and it is considered as a powerful decision-making tool. In the present paper, assessment of the failure probability of corroded pipeline subjected to internal pressure is estimated by using the first order reliability method (FORM). Measurements of defect dimensions have been achieved changed into collected by using ultra sound inspection probe through a 75-km pipeline portion on one of the main Algerian high pressure gas transportation that has been in service for 30 years. The sensitivity analyses have been carried out on random variables to identify the importance of the parameters within the reliability mechanical model. The modified B31G code has been coupled as a mechanical model, with Rackwitz optimization algorithm by using PHIMECA Software. The limit state function resumes the difference between the pipeline burst pressure and the pipeline operating pressure. The aim of the present work is to make in evidence the competitive importance of pressure service, wall thickness and the defect depth with regards to defect length and to determine the influence of the coefficients of variation on the failure probability and the remaining life of the pipeline. A diagram based on the reliability index results is proposed to predict the pipeline degradation and it can be used as a decision tool for maintenance program. Voir les détails

Mots clés : corrosion, Failure probability, Coefficient of variation, Modified ASME B31G

Engineering modeling of wear profiles in tooth flank of polyamidespur gears

Oualid GHELLOUDJ, Djamel Zelmati, Abdelaziz AMIRAT  (2017)
Publication

The present paper is a contribution in developing an engineering model expressing the evolution of tooth flank wear in polyamide spur gears as a function of number of cycles. The method is based on first observing the behavior of wear on tooth flanks in real test conditions. Then progressive flank wear profiles are plotted in order to sort out the corresponding fitting curves together with the associated mathematical equations. The general engineering model controlling the evolution of wear profile is found of the form of quadratic equation where the variable is the circular thickness of a tooth at a given depth from the top land of the tooth. The respective parameters of the engineering wear equation are determined as a function of number of revolutions of the spur gear. A wear correction parameter kw is added in order to catch up the measuring errors when plotting the wear profile curves using the proposed engineering wear model for spur gears. The data are in good agreement with that obtained from experimental measurements. Voir les détails

Mots clés : polyamide, Spur gear, wear, Tooth flank, lubrication

EFFECT OF ELECTRICAL CURRENT ON FRICTION AND WEAR BEHAVIOR OF COPPER AGAINST GRAPHITE FOR LOW SLIDING SPEEDS

Abdeldjalil BENFOUGHAL, Ali BOUCHOUCHA, Youcef MOUADJI  (2018)
Publication

Copper-graphite is an important tribological material used in the applications of electrical sliding contact like generators and electrical brushes. A series of experimental tests were conducted on a pin-disc tribometer in air and dry sliding condition. The pair of material was subjected to electric current ranging from 0 to 10A, normal loads of 5 to 30N and sliding speed of 0.5m/s. The duration of each test was 30 minutes. Experimental results indicated that the friction coefficient decreases and wear rate increases with increasing load with and without applied electric current. The changes in surface chemistry and topography of the tribo-surfaces were characterized using Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). This later technique was used to analyze the transfer of pin materials to the counterface, and also to understand how copper and graphite influence the tribological properties. Results indicated that, electric current and normal load have more or less significant influence on the tribological behavior of the pair of materials and the effect of oxide layer created at interface of the pairs in contact. Voir les détails

Mots clés : friction, wear, Contact temperature, load, Electric current.

Estimated life time in an HDPE pipe with a semi-elliptical defect under internal pressure

L. Alimi, K. Chaoui, M. HASSANI, A. Azzi  (2017)
Publication

High density polyethylene has been widely used in marine and gas transportation, storm sewers, culverts and city drainage system. Compared with other conventional pipes, it has its own advantages, such as, chemical and corrosion resistance, toughness, flexibility, easy splicing and consequent easy handling and installation. In this paper, and in order to predict the remaining lifetime of a pipe having a defect and subjected to internal pressure, it is necessary to estimate KI stress intensity factor during the propagation of the crack. The finite element method is used to assess the values of the stress intensity factor of an axially oriented semi-elliptical crack located at the inner surface of an HDPE pipe. The crack configuration is described by the relative wall thickness (t/R), the relative crack depth (a/t) and the crack aspect ratio (a/c). The lifetimes presented are discussed according to the size of the crack and the stress intensity factor in each case. Voir les détails

Mots clés : HDPE pipe, Crack, rupture, Finite Element Method FEM, stress intensity factor, Lifetime

Estimated life time in an HDPE pipe with a semi-elliptical defect under internal pressure.

L. Alimi, K. Chaoui, M. HASSANI  (2017)
Article de conférence

High density polyethylene has been widely used in marine and gas transportation, storm sewers, culverts and city drainage system. Compared with other conventional pipes, it has its own advantages, such as, chemical and corrosion resistance, toughness, flexibility, easy splicing and consequent easy handling and installation. In this paper, and in order to predict the remaining lifetime of a pipe having a defect and subjected to internal pressure, it is necessary to estimate KI stress intensity factor during the propagation of the crack. The finite element method is used to assess the values of the stress intensity factor of an axially oriented semi-elliptical crack located at the inner surface of an HDPE pipe. The crack configuration is described by the relative wall thickness (t/R), the relative crack depth (a/t) and the crack aspect ratio (a/c). The lifetimes presented are discussed according to the size of the crack and the stress intensity factor in each case. Voir les détails

Mots clés : HDPE pipe, Crack, rupture, Finite Element Method FEM, stress intensity factor, Lifetime.