Liste des communications
Crack propagation resistance in hydrocarbon transport pipelines
The aim of this paper is to determine the propagation resistance of cracks in grade API 5L X70 steel pipes. These pipes are produced by the Algerian company of manufacture of welded pipes (ALFAPIPE), they are intended for the transport of the hydrocarbons. Mechanical tests such as resilience and tensile strength were carried out on specimens taken from pipe ferrules in the longitudinal and transverse directions. The resilience tests are carried out at different temperatures in order to calculate the stress intensity factor. Tensile tests are used to have the mechanical characteristics of the material. The experimental results are then exploited in the modeling part by the software of calculation of the structures using the method of the finite elements, the calculation code is CASTEM 2016. Voir les détails
Mots clés : Tenacity, fracture, Resilience, Modeling.
Influence of heat treatment on the structure and abrasion wear of A105N steel
Wear is the removal of material from a surface by very different mechanisms such as abrasion, erosion, fatigue and corrosion. In the industrial sector, the cost of repairing used parts is very high; the solution in this case is to choose an anti-wear material. To choose an anti-wear material, the first factor is the identification of wear type; however, the conditions of use in the industry are complex so the choice of materials is difficult.Usually the choice of material depends on several factors such as high hardness, high resistance to abrasive wear and low friction coefficient. Thermal treatments are proposed in order to improve these properties. The objective of our work is to study the influence of heat treatment on the structure and abrasion resistance behavior of A105N steel.Samples solution treatment is carried out at a temperature of 900 °C for 2 h then quenched in water. Experimental techniques such as optical microscopy, SEM, EDX and abrasion wear test are used to highlight the effect of heat treatment on the wear resistance of the steel.The microstructural characterization shows that in the initial state, the structure is composed of ferrite and perlite, after tempering, the structure is composed of perlite and bainite. The wear tests by abrasion show a clear difference on the weight losses of up to 50% following the quenching treatment. Voir les détails
Mots clés : wear, abrasion, steel, heat treatment, A105N.
Simplified modeling to avoid breakage of sheet metal during tandem rolling
In the tandem rolling, the simultaneous passage of the sheet between multiple cages poses a control problem of inter-stand tension [1,2]. Manufacturers tend to ask the equal tension between a cage and another, that is to say between the output of a cage and the input of the next cage. This causes a speed regulation problem. Indeed, this generally gives different speeds between the input and pass out of the previous pass. Which may lead to ripples or excessive tension may cause breakage of the strips. To illustrate this situation, we propose to take the data from the tandem mill site steel complex Arcelor-Mittal El Hadjar Algeria. It contains five stand tandem mill. The purpose of this work is to get to determine for each case, the correction to be made to obtain equal speeds and tensions between the output of each cage and the door of the cage that follows.To our simplified calculation model, two Matlab program was developed:-the first: Greenhouse to the rolling calculation (speeds, the neutral plane, ....)-the second: to make corrections tensions in order to obtain equal speed between the output of a cage and the input of the next cage.The Results show the convergence speed after the correction of tension, like that, to avoid the risk of breakage or undulation of the rolled strip and pre calculated magnitudes we do not stray from reality. Voir les détails
Mots clés : modeling, rolling, tension, speed., breakage
EFFECTS OF TOLUENE-METHANOL MIXTURE ON MECHANICAL AND STRUCTURAL PROPERTIES OF HDPE PIPE
The aging of pipes is an economic and technical challenge for drinkable water and natural gas networks. The degradation of HDPE pipes depends on factors such as age, laying and service conditions, environmental temperature, fluids and soils corrosiveness, density and traffic loads. In service, polymer structures are often exposed to aggressive environmental stresses such as UV’s, oxygen, acids, bases and solvents, affecting the nature of the material as well as its microstructure, physical status and chemical composition. Various studies have presented results on HDPE pipes embrittlement, focusing on cracking phenomena under environmental stress cracking, creeping and fatigue cracking. The weakening of the material usually resulted from mechanical behavior modifications which made it unable to withstand loads without breaking under normal service conditions. In this study, we attempted to assess the effects of an equimolar toluene-methanol mixture while considering exposure to air and water as references. Morphological properties such as crystallinity, crystalline lamellae thickness and the oxidation induction time (OIT) are studied using differential scanning calorimetry in order to establish the extent of degradation using DSC. Mechanical tests and thermal analysis show that toluene-methanol mixture is much more absorbed by the resin compared to water, i.e. the degradation is very pronounced. In terms of mechanical properties (E, σy and εf), the nominal values collapsed. In addition, the study shows the evolution of these parameters as a function of pipe thickness in order to get an idea about structural heterogeneity across pipe wall. An increase in the crystallinity together with crystalline lamellae thickness is observed which is confirmed by literature for other organic solutions. This phenomenon is known as chemical-crystallization due to the shrinkage of the amorphous phase during possible chain segmentation process. Voir les détails
Mots clés : HDPE; Environmental effect; Aging; Mechanical properties; Crystallinity; OIT
Approche expérimentale pour la détermination de la distribution des contraintes résiduelles dans un pipe en polyéthylène.
Dans cette étude la détermination des contraintes résiduelles dans un tube en polyéthylène de diamètre 125mm destiné au transport du gaz naturel est réalisée sur la base d’une approche expérimentale. La technique d’usinage successif par enlèvement de matière est utilisée. La paroi du tube est divisée en cinq couches. Les couches découpées suivant la même génératrice ont permis d’identifier la distribution des contraintes résiduelles relaxées dans le tube au cours du temps. Il a été trouvé que des contraintes compressives sont relaxées dans l’extérieur de la paroi. Et d’autres contraintes positives de traction sont libérées à l’intérieur de la paroi. Cette configuration est liée au procédé de fabrication à savoir l’extrusion. Voir les détails
Mots clés : extrusion, Pipe, refroidissement, usinage, contrainte résiduelle
Comparative Performance Study between DTC_C and DTNC Multi-level Inverter Fed DSIM
A comparative performance study between the classical direct torque control (DTC_C) and that of a direct torque control improved by applying the technique of artificial intelligence based on the neural network (DTNC) is proposed in this paper. The command is applied to a double-stator induction machine (DSIM) fed by a multi-level inverter. Simulation results of the speed control of the machine and the improvement of the torque and the flux by reducing the fluctuations are studied by illustrating the DTNC merits compared to the classical DTC_C. Voir les détails
Mots clés : A double-Stator Induction Machine, Direct Torque Control, Neural Network, Multi-level Inverter.
A summary of Vibration analysis techniques forfault detection and diagnosis in bearing
Bearing is one of the most critical components ofrotating machinery .They are employed to support and rotate theshafts in rotating machinery. Therefore; any fault in the bearingscan lead to losses on the level of production and equipments aswell as the creation of an unsafe working environment forhumans. For that reason, the bearing fault diagnosis has receivedconsiderable attention from the research and engineeringcommunities in recent years. The purpose of this study is toreview the Vibration analysis techniques and explore theircapabilities, advantages and disadvantage in monitoring rollingelement bearings. Voir les détails
Mots clés : Vibration analysis, bearing Fault diagnosis, Fast Fourier Transform (FFT), Envelope Analysis (EA), Short Time Fourier Transform (STFT), Empirical Mode Decomposition (EMD)
EFFECT OF MULTI-PASS HOT ROLLING ON RECRYSTALLISATION BEHAVIOUR OF FERRITIC STAINLESS STEEL TYPE 409
The aim of this research is to study the effect of interrupted deformation on the recrystallisation behaviour of ferritic stainless steel type 409. Hot rolling schedules have been performed on an experimental rolling mill using rectangular slabs of this ferritic stainless steel.The research has been carried out using material of ferritic stainless steel type 409, which contains precipitates, initially using experimental rolling of small slabs and quantitative optical metallographic techniques with one pass only. Stainless steel type 409 displays a slower rate of recrystallisation than other ferritic stainless steels and this is attributed to the presence of titanium.The effects of static recovery and full static recrystallisation between two passes on subsequent recrystallisation kinetics have been investigated. In this stainless steel, when recovery occurs between the passes, subsequent recrystallisation is retarded compared with that for a single pass of the combined strain. Increasing the recovery time increases the retardation of recrystallisation even more. Also it has been found that when recrystallisation is complete between the two passes, the rate of subsequent recrystallisation after the second deformation was considerably accelerated. Voir les détails
Mots clés : ferritic stainless steel type 409, precipitates, hot rolling, dynamic recovery, static recovery, static recrystallization.
Frittage de l’Hydroxyapatite HA poreuses élaborées
Au cours des dernières années, la nécessité de substituer et la réparation des tissus endommagés durs (os, articulations, dents) a augmenté en raison de maladies et les blessures.Avec la demande croissante de matériaux bioactifs pour orthopédique ainsi que la chirurgie maxillo-faciale, l'utilisation d'hydroxyapatite HA en tant que charges, les espacements et des substituts de greffe osseuse a reçu une grande attention surtout au cours des deux dernières décennies, principalement en raison de leur biocompatibilité, bioactivité et ostéoconduction en ce qui concerne les caractéristiques pour accueillir les tissus.Nous allons présenter le mode d’élaboration du d'hydroxyapatite, ensuite la densification de pastilles poreuses pour le teste de régénération. Voir les détails
Mots clés : élaboration, hydroxyapatite, frittage, porosité
Elaboration and characterization of thin solid films containing cerium
Cerium oxide films are widely studied as a promising alternative to Cr(VI) based pre-treatments for the corrosion protection of different metals and alloys. Cathodic electrodeposition of Cerium containing thin films was realised on TA6V substrates from a Ce(NO3)3,6H2O and mixed water-ethyl alcohol solutions at 0.01 M. Experimental conditions to obtain homogeneous and crack free thin films were determined. The deposited cerium quantity appears proportional to the quantity of electricity used, as indicated by the Faraday law. Subsequent thermal treatment lead to a CeO2 coating, expected to provide an increase of TA6V oxidation resistance at high temperatures. The deposits were characterized by differential scanning calorimetry (DSC), optical and scanning electron microscopies.Titanium and its alloys have been considered as one of the best engineering materials for use in industrial application due to their high specific strength, good corrosion resistance and biocompatibility [1-3].However, a major problem of titanium alloys is an insufficient wear resistance and serious oxidation at high temperature [4,5].To combat this problem, conversion coatings are widely used as part of the corrosion protection system [6]. The use of rare-earth compounds particularly cerium compounds have attracted significant attention for corrosion protection of metals and alloys as a result of new environmental regulations to replace toxic compounds [7, 8]. Cathodic electrodeposition has been used because of the low cost of equipment and of precise control of deposited thickness [9,10]. The focus of this study is on cerium based conversion coatings, wich have shown promise as potential replacements for chromates [11,12]. In the present work, an electrodeposition technique was used to get, in one step, thin cerium containing films over all surfaces of TA6V samples. The deposits were then submitted to a thermal treatment under argon in order to get a CeO2 coating, the aim being to later study the behaviour of such a coated material under high temperature oxidation conditions.The electrochemical bath was a 0.01 M Ce(NO3)3 solution, obtained by dissolving commercial cerium nitrate (Ce(NO3)3, 6H2O, 99.99% purity) in water 50 vol.% ethyl alcohol. Electrodeposition was realised using a classical three electrode experimental set-up, described elsewhere [13,14], including a TA6V sample as cathode, a platinum grid counter electrode and a saturated calomel electrode (SCE) as reference. Deposition experiments were carried out in galvanostatic mode, current density varying from j= -2 to - 0.05 mA cm-2, at ambient temperature and without stirring. Deposition time was varied from 100 to 7200 s. The variation of the potential versus time was recorded during deposition. After electrodeposition, samples were rinsed with ethyl alcohol and air dried for at least a night before further use or analysis. These experimental conditions were chosen from previous work [14] and were expected to provide thin films with a thickness in the range 50–500 nm.The aim of this work was to determine adequate parameters for cathodic electrolytic deposition, on TA6V substrate, of cerium hydroxide films from mixed water–ethyl alcohol solutions to obtain, after a thermal treatment, thin CeO2 films(<500 nm), suitable for high temperature purposes. The deposit weight and hence the deposit thickness was shown to increase with current density at a constant deposition time. However, low current densities (-0.2 mA.cm-2) promoted the formation of thin, crack-free films (which was not the case for higher current densities). The deposited cerium quantity appears proportional to the quantity of electricity used, as indicated by the Faraday law. Microscopic observations (-0.2 mA.cm-2) revealed that formed cerium hydroxide films are uniformly deposited all over the sample surfaces. The results of the DSC analysis are in perfect concordance with the literature. This study thus illustrates that electrolytic deposition can be used to obtain thin and uniform cerium films over a metallic substrate used as the cathode. High temperature oxidation experiments are currently performed on coated specimens. First results are quite promising. Voir les détails
Mots clés : electrodeposition, Cerium oxide, Cthodic deposit, Titanium alloy.