Liste des documents

Nombre total de résultats : 1994
Pertinence Titre A-Z Plus récents Plus anciens
10 25 50
Année de publication

Caractérisation physico-chimique et électrochimique d’un soudage par friction rotative

Mémoire de Master

The objective of This dissertation of master is to perform rotary friction welding . the first is to carry out a homogeneous welding by varying the speed of rotation and the second is to carry a heterogeneous welding AL2017/ Steel 304L . We follow a physico-chemical and electrochemical characterization on its two types of welding . Voir les détails

Mots clés : Rotary friction welding, AL2017/ Steel 304L, types of welding

Caractérisation mécanique jonctions d’assemblables :acier inoxydable 304L /alliages de types ZY-4

ch. Charikhi, M.Y. Yendjah  (2022)
Mémoire de Master

In order to avoid or minimize the appearance of the harmful phases in the zone of diffusion of the works employed aiming at controlling the flow of diffusion of the chemical elements through the interface, although studies are undertaken, the nature of the compounds, the formation kinetics of certain phases and the number of zones formed at the interface in the temperatures of their practices, between 950-1100°C, remain controversial. The data related to the compromises between the operating parameters of the welding thermal cycle, in particular the temperature and the holding time of the isothermal bearing during a direct bond Zy4/steel are not very developed in the literature. The recent results obtained on the shape of the interface and the nature of the phases formed which will serve as a basis for the interpretation of the results which will be obtained and presented in the last chapter. The ZPR consists of three layers regardless of the holding temperature The CI ~ 4 to 6 μm thick type - is located on the steel side. The thickness CII is practically independent of temperature, formed of a mixture of ε+Zr2 phases between 950 and 1020°C and of ε+-Zr phases for T=1050°C. Its thickness as well as its microstructure strongly depend on the holding temperature. The thickness of the ZPR evolves continuously up to 1020°C and increases drastically when T=1050°C . Results obtained from the evolution of the thickness of the reaction product zone as a function of residence time e=f, used to define the experimental parameters are used to select the thickness of the ZPR. During these steps the liquid fraction is gradually increasing and the thickness of CIII becomes drastically enlarged after 45 minutes of isothermal holding. Voir les détails

Mots clés : diffusion of the chemical elements, harmful phases

Détection des feux de forêts en utilisant les images aériennes acquises par drone et le modèle YOLOv3

Mémoire de Master

Forest fires in recent years have destroyed hundreds of thousands of hectares and caused the death of several people, these fires also have a significant economic cost. In this work, we propose an approach for an early wildfire detection, before their development into fires, because it is difficult to control them afterwards. The approach is based on the processing of aerial data acquired by unmanned aerial vehicles (UAV), and the automatic early wildfire detection, which allows to send an emergency alert directly to the relevant services and a to have a fast response. The technique used is based on transfer learning applied on a model of object detection which is YOLOv3, then validate the effectiveness of the model using the datasets of Flame, FiSmo and other images. The performances obtained in terms of Recall, F1-Score, Accuracy and Precision are respectively: 95.535%, 95.085%, 92.559%, and 96.428%. Voir les détails

Mots clés : Drone, Wildfire, Forests, YOLOv3, Detection.

Conception et commande d'une machine de soudage de type TIG

Y.Messad  (2018)
Mémoire de Master

TIG welding machine are higly used in mostof industries.this work consists of the desing and engineering of a welding machine. Voir les détails

Mots clés : arc welding, TIG generator, DC/DC convertor

Modélisation du comportement mécanique des constituants du palmier dattier

GUETTAF TEMAM Tahar (2017)
Thèse de doctorat

Dans les régions arides et semi arides, nous retrouvons les palmiers dattiers en masseet cette richesse joue un role important au dévellopement de ces dernières, spécialement dansl’activité économique et sociale. Sachant que la datte est le fruit des palmiers mais reste à savoirqu’il dispose aussi d’un bois de tronc et de palmes assez important utilisés dans les fabricationstraditionnelles relatives à ces régions ou entant qu’engrais fertilisant les terres utiles, cespratiques sont limitées raison du manque de données scientifiques et techniques dans cedomaine. Dans otre recherche une large base de données techniques aussi physique, technique tmicroscopique définissant l’aspect morphologique des fibres et du bois des variétés Deglet Nour,Mech Degla et El Ghers pris encharge par cette étude de recherche. Des caractérisations on étéréalisées telle que la microscopie optique, le taux d’absorption et le taux d’humidité ont révélésbeaucoup de déductions aussi des tests mécaniques telle que les tests de traction ont été réalisés. Voir les détails

Mots clés : Palmier, palmier dattier, bois, microstructure de bois, caractérisation mécanique, modélisation

Surface performances of Ti-6Al-4V substrates coated PVD multilayered filmsin biological environments


Multilayered and nanostructured coatings of Ti based alloys (oxides and nitrides) are elaborated and tested for increasing protective properties such as corrosion and wear resistances. A pin-on-disc tribometer was used to evaluate the wear resistance in Hank's solution against bovine bone. Corrosion behavior in Hank's solution was determined by potentiodynamic and electrochemical impedance spectroscopy techniques. Besides, the specimen surfaces were characterized by Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) microanalyses. The results showed that optimal tribological properties were obtained in the case of coatings having TiN as top layer. The main wear mechanism was abrasive third bodywear. In vitro corrosion tests at 37 °C showed that the better corrosion resistance was obtained when TiN was the top layer. However all of them exhibited good tribological properties, good corrosion resistance and then may be promising options for biomedical applications. Voir les détails

Mots clés : PVD coatings, oxides, Nitrides, Biomaterials, tribology, corrosion

Dry sliding wear performance of an annealed TiNi alloy with differentnickel contents

Soumaya MEDDAH, Hacene Chadli, Mounira Bourebia, Alex Montagne, Alain Iost, Mohamed Labaiz, Ahlem Taleb  (2020)

The wear behaviour of the TiNi alloy tested at different conditions (2 and 4Nas applied loads and 40,50 an 60 wt%as nickel contents) was investigated. For this purpose, two main experimentaltechniques consisting of wear and indentation tests were used. Scanning electron microscopy (SEM)and laser source profilometry were employed to reveal the wear mechanisms and the affected wornsurfaces. Furthermore, design of experiments planning introducing factorial design as well as responsesurface was adopted to attempt predicting the coefficient friction according to the planned testparameters. Nanoindentation results showed that all the TiNi alloys are harder than a TA6V4 alloywhich is commonly used in dental implant. Particularly, the TiNi60 alloy exhibited superiorsuperelasticity, characterized by a lower E/Hratio and a higher depth recovery ratio than the TA6V4alloy. Besides, the wear rates underwent a substantial increase with the increase of the applied load buta decrease with increasing the Ni content. The worn surfaces analyses revealed an enhanced resistanceto adhesive and abrasive wear with increasing nickel content. Voir les détails

Mots clés : TiNi alloy, factorial design, Wear Resistance, superplastic behaviour

Effect of ball burnishing process on mechanical propertiesand impact behavior of S355JR steel

Mounira Bourebia, Hamid Hamadache, Laouar Lakhdar, Zoheir MENTOURI, Djemili Kamila, Hazem Tarek, Taleb Ahlem  (2021)

Often, surface mechanical treatment (SMT) or heat (quenching, tempering) is used to improve the surface condition andmechanical characteristics such as impact resistance and tensile strength. Hence the objective of this experimental work, whereball burnishing (BB) as well as quenching and tempering were applied on S355 JR steel specimens, is to evaluate the surfacehardness Hv, the rupture strength Rm, the energy absorbed W during the impact test, and the work-hardened thickness e after theburnishing operation. Factorial designs were used for the test organization and mathematical models were established for theprediction of Hv, Rm, W, and “e” in function on treatment parameters considered: number of tool passes (i) and the pressure force(Py). The results show that the surface hardness increases by 30.46%. The high levels of Py and i were allowed to improve Rm by30.8% as well as an increase in tenacity of only 3.6%. Increasing the force to 20kgf promotes mixed rupture under the effect ofimpact to shock. The quenching and tempering improve the Rupture strength Rm by 183% and 119%, respectively, while theeffect of burnishing was limited to a rate of increase of this property of 28% compared to machining. Voir les détails

Mots clés : Tensile resistance . Burnishing . Heat treatment . Superficial hardness . Absorbed energy . Penetration depth . Ruptures facies

Experimental Study Of The Effect Of Shot Peening Parameters On The Surface Texture - Influence On The Adhesion Of A Paint Coating

M.Bourebia, S.Meddah, Z.Mentouri, A.Oulabbas, S.Achouri, L.Laouar  (2022)

The investigation presented in this paper focuses on the effect of surface texture on the adhesion of a paint coating as well as the influence of shot peening regime parameters on the surface isotropy indicator "Str" and on the fractal dimension "Df". The tests have been organized according to full factorial designs 23, where three parameters have been examined, at their two levels (min, max), namely the pressure (P), the angle of attack (θ) and the time (t). 3D roughness measurements have been carried out to characterize the different surfaces after a shot peening operation. A mathematical model linking the input parameters (P, θ, t) and the output parameter "Str", in the study area has been established, and the fractal dimension (Df) has been used for the surface characterization. Paint deposit has been applied to surfaces and adhesion tests have been carried out. The results show the significant effect of the impact angle on "Str", and the interaction between the different parameters in the studied area. Furthermore, the greatest bond strength has been obtained with the sample 3 (F = 4.25 N / mm2), whose the isotropy indicator "Str" is equal to 0.6438 and the fractal dimension Df = is about 1.768. Voir les détails

Mots clés : surface texture, fractal dimension, shot peening, Adhesion

Inhibition Effect of 2,2’-bipyridyl on the Corrosion of Austenitic Stainless Steel in 0.5M H2SO4


The corrosion inhibition of AISI309 austenitic stainless steel by 2,2'-Bipyridyl in 0.5MH2SO4 at 298K was studied using the mass loss’ method, the potentiodynamic polarization (Tafel), the linear polarization (LRP), and the electrochemical impedance spectroscopy (EIS). The results showed a mixed inhibition mode and an increase in the charge transfer resistance, due to inhibitor molecules' adsorption at steel surface. This latter obeys to Langmuir isotherm. The observation by scanning electron microscopy (SEM) and the analysis by energy dispersion spectrometry(EDS) confirm an inhibitor film’s presence. The calculated inhibition efficiencies are in accordance with 87.78% maximum value. Voir les détails

Mots clés : AISI309, 2, 2'-Bipyridyl, EIS, Tafel, corrosion, inhibition