CRTI Library

Détermination expérimentalement et numériquement des paramètres de rupture à l'aide de la technique de corrélation d'image digitales DIC et l'analyse FEM

For the purpose of determining the critical fracture parameters of materials such as the critical energy restitution rate GIc, the stress intensity factor KIc, the maximum fracture load and the critical crack opening CTOD where δc numerous approaches are used in the literature. One of the approaches is based on experimental tests assisted by numerical methods such as Digital Images Correlation DIC and FEM finite element analysis. A FEM finite element analysis under a computation code (ABAQUS) allows to simulate the rupture tests, through numerical models in elasticity or elasto-plasticity allows to extract the values of the different components of the displacement and deformation field, the latter are confronted with the same parameters obtained experimentally. And finally, the calculation of the energy restitution rate and the stress intensity factor as well as the critical opening of the CTOD cracks. Voir les détails

Mots clés : Critical failure parameter, The critical energy release rate GIc, The stress intensity factor KIc, The maximum breaking load

Réalisation d'un système de navigation d’un quadricoptère piloté par carte Raspberry Pi

This thesis is devoted to the realization of a navigation system specific to the quadricopter based on the Raspberry Pi 3 B development board. The latter must acquire and process in real time the information from the MPU6050 and GPS sensors, integrate scenes captured by a Pi camera integrated with the system produced, command and control the quadcopter remotely via a joystick and a smartphone. The results obtained by the sensors and the camera to be displayed on the smartphone, which represents the ground station. Voir les détails

Mots clés : UAV, quadricopter, navigation system, Raspberry Pi 3B, MPU6050, GPS, real time, Pi camera, joystick, smartphone.

Experimental, Mechanical Characterizations of Friction Welding of Steel and Aluminium Joints

Rotary friction welding (RFW) is a solid-state joining process which works by rotating one workpiece relative to another while under a compressive axial force, which produces coalescence of materials workpieces. It is considered most viable alternative to overcome the difficulties faced in conventional joining techniques. As it is a solid state welding process, the process does not form molten pool thereby eliminating the solidification errors. It offers many advantages for some manufacturing sectors for a wide range of applications. In this research, we investigated the mechanical and metallurgical characteristics of RFW welded joints for homogenous and heterogeneous assemblies. We have studied A60 steels and 2017A series aluminum alloys. The obtained welds are similar in appearance in that they have several Microstructural distinct zones.So, the results show that by increasing the rotating speed employing 1000 and 1600 rpm, the mechanical properties during the RFW process is lightly improved, favored by the increase in heat flow. In the same specimen, the microhardness distribution is generally viewed lightly changed between center line throw weld of welded tube and close to their boundary line. This is due to the no-uniform of temperature distribution in cross section. Thus, plastic deformation of heated portion of the metal plays an important role in friction welding process and their quality. Microstructural analysis reveals that grain growth in the joint WCZ and in heat affected zone HAZ because of the no-uniform of thermal flux distribution in both directions (transvers and longitudinal of tube). Finally using RFW, the fabricators allow to perform and maintenance the mechanical components with low cost and which it conserves their welding quality compared to the classical fusion welding. Voir les détails

Mots clés : Rotary friction welding (RFW), plasticised material, heat flux, characterization, Microhardness

The Microstructure, Texture and Mechanical Propertiesof Friction Stir Welded Aluminum Alloy

The microstructure and texture of 7075-T6 FSW weld with optimal parameters are investigatedusing optical microscopy, electron back scatter diffraction and neutron diffraction. The mechanical proper-ties are characterized through microhardness, nanoindent ation and ultrasonic tests. The friction stir weldingis performed at a nominal rotational speed of 1400 rpm and a traverse speed of 60 mm/min. The nugget zonecontained fine, equiaxed and fully recrystallized grains. The texture of the base material mainly consisted ofCube and rotated Goss components. However, in the nugget zone, the dominant texture components were Band among common shear orientations. Elastic modulus was measured by ultrasonic and nanoindentationmethods. The ultrasonic method being nondestructive, easy, inexpensive and fast. It is found that a littleincrease of Young modulus is observed in nugget zone compared to base metal. Voir les détails

Mots clés : Aluminum alloy, FSW, microstructure, texture, Microhardness, Young modulus

CoSoTIA Project: Decision Support for the Choice of Concentrated Solar Technologies for Electricity Generation

The C oSoTIA (Concentrated Solar Technologies for I ndustrial Appli-cations) project initiated by the CRTI center in collaboration with the URMPEunit concerns the s tudy and development of CSP s olar concentrators f or indus-trial applications. I n t he present work, we present decision s upport t ools f or thechoice of a s olar concentration t echnology for s ites i n Algeria. T hey will be usedfor t he comparison between diff erent t echnologies of solar concentration e.g.:cylindro-parabolic, parabolic, s olar tower, etc. T he models used include projectcosts and site characteristics; they incorporate also engineering knowledge (eco-nomic, social, t echnical and environmental). The i nformation needed for decision-making produced by these t ools i s: the t otal cost of the project, i ndicators witheconomic, social, t echnical and environmental aspects. The case s tudies presentedwere conducted under t he SAM Advisor environment, which was developed t oevaluate the capacities t o i mplement C SP project i n order to produce expertisefor t he diff erent actors t hrough an application on a given s ite (by t he client). Fourcase sites i n Algeria and f or two t ypes of s olar concentrator plant are studied andpresented. A comparative study was conducted and for each s ite the best C SP wasdeduced and commented. Voir les détails

Mots clés : Decision support, Multicriteria analysis, Solar concentration, CSP, SAM Advisor

Weldability, microstructure, and residual stress in Al/Cu and Cu/Alfriction stir spot weld joints with Zn interlayer

In this work, the effect of lap joint configuration and Zn interlayer addition on the microstructure, the residual stress state, and thequality of Al/Cu (configuration #1) and Cu/Al (configuration #2) friction stir spot welds (FSSW) was investigated. The studyrevealed the close dependency of the weld joint quality on the pin length and Zn addition. The higher the pin plunge depth is, thegreater the obtained tensile shear strength. The Zn addition reduced sensibly the thickness of Al2Cu layer (from 10 to 2 μm) andfavored the formation of the Al4.2Cu3.2Zn0.7 precipitate that hindered the formation of detrimental Al4Cu9compounds. Materialflow analysis revealed the presence of an intermixing zone containing thin continuous intermetallic layer (approximately 2.07 μm) at the weld interface of configuration #1. Meanwhile, the Cu material was covered by the Zn layer, which resultedin a hardness increase (228 HV) at the stirred zone. In addition, a significant increase of the tensile shear strength from 1650 to 3600 N was noticed (an improvement rate of ≈ 118%). Conversely, in configuration #2, the Zn foil was squeezed out of the spotweld interface resulting in the absence of material intermixing, discontinuous intermetallic layer, low hardness level (140 HV),and weak improvement rate of the shear strength (≈ 53%). The Zn interlayer addition resulted in a quasi-symmetric distribution ofthe residual stresses and shifted their nature from tensile stresses (+ 60 MPa) to compressive ones ( − 10 MPa). Voir les détails

Mots clés : FSSW, aluminum, copper, Zinc interlayer, Tensile shear, microstructure, intermetallic Compounds, residual stress

Conception d’un autopilote pour un drone léger type quadri-rotor

This dissertation is divided into two important parts: the first part is dedicated to the establishment of the dynamic quadrotor model to study its stability and control under MATLAB. The second part is reserved for the realization of an autopilot card for the quadrotor that should be compatible with Arduino MEGA development board. This card must be able to acquire and process information from the MPU6050 and GPS sensors in real time, to order and control the quadrotor. The results obtained by the sensors must be displayed on a graphical interface representing the ground station. Voir les détails

Mots clés : Quadrotor, autopilot, Arduino MEGA, GPS, MPU6050, ground station, real time, MATLAB.

Comparison in Temperature evolution and Mechanical properties of an aluminium alloy welded by FSW and TIG processes

The purpose of this study is to show the potentiality of Friction Stir Welding (FSW) for joining the 2017A aluminium alloy, which is difficult to be welded by fusion techniques. A comparative study of FSW with a conventional fusion process as Tungsten Inert Gas (TIG) is made. FSW welds are made up using a specific tool mounted on a milling machine, however a single pass welding was applied to obtain a TIG joint. Thereafter, the comparison between the two processes has been made on the mechanical properties and thermal behavior. The results show that the thermal cycle peak induced by FSW process are lower than that induced by TIG process about 25%. Because the FSW does not need to melt the materials during welding. Microstructural examination revealed the grains refinement of the FSW weld joints that induce better mechanical properties (tensile tests and microhardness), higher joint efficiency (more than 80%) and good ductility compared to TIG joint. FSW process currently opens a great opportunity of application in the industrial and transport fields. Voir les détails

Mots clés : FSW, TIG, aluminum, Temperature, tensile joint efficiency, Microhardness

Temperature Evolution, Microstructure and Mechanical Properties of Heat-Treatable Aluminum Alloy Welded by Friction Stir Welding: Comparison with Tungsten Inert Gas

Friction Stir Welding (FSW) is a solid-state welding technique that can join material without melting the plates to be welded. In this work, we are interested to demonstrate the potentiality of FSW for joining the heat-treatable aluminum alloy 2024-T3 which is reputed as difficult to be welded by fusion techniques. Ther eafter, the FSW joint is compared with another one obtained from a conventional fusion process Tungsten Inert Gas (TIG). FSW welds are made up using an FSW tool mounted on a milling machine. Single pass welding was applied to fabricated TIG joint. The comparison between the two processes has been made on the temperature evolution, mechanical and microstructure behavior. The microstructural examination revealed that FSW weld is composed of four zones: Base metal (BM), Heat affected zone (HAZ), Thermo-mechanical affected zone (THAZ) and the nugget zone (NZ). The NZ exhibits a recrystallized equiaxed refined grains that induce better mechanical properties and good ductility compared to TIG joint where the grains have a larger size in the welded region compared with the BM due to the elevated heat input. The microhardness results show that, in FSW weld, the THAZ contains the lowest microhardness values and increase in the NZ; however, in TIG process, the lowest values are localized on the NZ. Voir les détails

Mots clés : Friction Stir Welding, tungsten inert gaz, aluminum, microstructure

Edge detection in an infrared image in steeland metallurgical domain

The iron and steel domain has a very important role in the industry. Indeed, much research has been fixed to the product quality, which is an essential factor in the production cycle. Among the most used techniques to today, to inspect the finished product, there is the infrared thermography. This latter allows for detecting defects in materials. Treatments of captured image using an infrared camera can detect the edge of these defects and hence locate them. In this work we try to apply mathematical methods to detect these edges. Voir les détails

Mots clés : Infrared thermography, materials, Defects, edges