Sciences des matériaux

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Non-destructive testing of cover concrete using spectral analysis of ultrasonic surface waves

Morad Grimes, Zoubir-Mehdi SBARTA, Nabil YACEF  (2016)
Article de conférence

Concrete cover evaluation with NDT technique is a critical issue in the diagnosis of structures service life. Ultrasonic NDT technique is one of the most efficient techniques for concrete strength evaluation. This paper presents the use of spectral analysis of ultrasonic surface waves for the non destructive evaluation of concrete cover in laboratory. The procedure consists in generation and reception of surface waves using the time of flight diffraction method. After extraction of the lateral wave in the received signal using the matching pursuit method, the phase velocity dispersion characteristic is determined, and concrete cover is characterized. Voir les détails

Mots clés : Time of flight diffraction, matching pursuit, concrete cover

Estimation of ultrasonic wave parameters in materials under bending force

Toufik Benkedidah, Morad Grimes, Abdelmalek BOUHADJERA  (2016)
Article de conférence

this paper presents the use of prism technique todetermine the longitudinal and transversal wave parameters in materials under simple bending forces. The weak number of studies on acoustoelastic behavior and the evolution of measurement methods led us to propose a complete feasibility study on measurements of longitudinal and shear waves for different mediums subjected to uniaxial compressive stresses.The expectation maximization algorithm is employed for parameters estimation those are amplitude, phase, time of flight, frequency and bandwidth. These parameters allow the verification of the parameter values modification resulting from the effect of bending stresses. Voir les détails

Mots clés : Ultrasonic, prism technique, expectation maximization algorithm

Fast Finite Element Computation for 3D Eddy Current Testing Problems with T-Ω Formulation

M. Hamel, H. Mohellebi, F. Hocini  (2016)
Article de conférence

The paper deals with T-Ω formulation modeling of eddy current problems. The method is applied to the analysis of 3D eddy current testing of metallic plate with cracks, and the usefulness of the method is investigated by comparing calculated results with measured ones. Voir les détails

Mots clés : nondestructive testing, Eddy Current, Cracks, T-Ω formulation, 3D finite element.

Study of the Effet of the Geometry Shape of defecton the Reliability of NDT Device

Z. Oudni, H. Mohellebi  (2016)
Article de conférence

This work concerns the study the effect of random properties and defect geometry on the reliability analysis ofthe non-destructive testing inspection device. Two kinds ofdefects geometries are considered as rectangle and triangle shapes respectively. A stochastic finite element method (SFEM) was used to solve the 2D electromagnetic equation incylindrical structure. The results obtained for both rectangle and triangle random shapes are given. Voir les détails

Mots clés : random geometry, random propertie, nondestructive testing, reiability analysis, stochastic finite elements

The Effect of Laser Treatment on the Erosion Resistance of a Copper -Nickel Austempered Ductile Iron

Mohamed H. Alaalam, Abdussalam M. Drah  (2016)
Article de conférence

The present work investigates the effect of laser surface hardening on the erosion resistance of alloyed austempered ductile iron contain 1.5% copper and 1.5% nickel austenitized for different austenitising times.Continuous wave of CO2 laser was used to heat by overlapping technique. The laser processing parameters used were; 1000 w, laser power, 1000 mm\min. Scanning speed and 40 L\min. Argon flow rate. After laser treatments erosion tests were carried out on the untreated and laser treated samples surfaces. The erodent particles used were pressurized silica +300 to 500 flows at speed of 50 m\sec. The erosion tests were performed at different angles 30°, 60° and 90°. Erosion tests showed significant reduction in the erosion rate after laser treatment at all impinging angles. Erosion resistance is improved depending on the impingement angle, (weight losses ingrams at 90° > weight losses in grams at 60° > weight losses ingrams at 30°). Increasing the impingement angle increases the erosion rate for both untreated and laser treated samples. This improvement in erosion resistance was attributed to the fine and homogenous structure, high hardness and the elimination of graph itenodules which were the source of notches. Voir les détails

Mots clés : laser treatment, erosion, ADI, austempering, hardness, austenitising

Acoustic Emission Monitoring of high risk installation in industrial environment

Hamid HAFID, Alain PROUST, Richard DUNOYER, Omar AL HAJ  (2016)
Article de conférence

Acoustic Emission (AE) technology is widely used to control in service pressure vessel in a wide range of industry. Acoustic emission monitoring and its benefits have long been known and utilized by many industries to optimize the use of structures, increase operational safety, and to save money through effective condition assessment and maintenance. The application and acceptance of AE monitoring within the civil engineering industry has greatly expandedin the past few years [1]. Among the technological progress of AE it is possible to apply the technology in Atex environment with industrial process giving some genuine information on propagating defects even in refining and petrochemical plants.The monitoring of critical equipment allows an early detection of significant defects and the ability of following their severity in serviceto give an alarm to improve the safety of equipments and particularly piping systems. Some industrial examples are given in this paper to shed into thelight the return of experience on AE long term monitoring. AE technology is used: to give an in situ diagnostic, to prevent catastrophic ruptures, to help to reduce maintenance costs, and to avoid shutdown with assessing risk based inspection. Voir les détails

Mots clés : Accoustic Emission, Monitoring

Contribution to the minimization of vibration ofrotating machines

Merazi Sayah  (2016)
Article de conférence

Rotating machines are used in areas as diverse as transport (trainsmotorized vehicles, etc.) Production industry, or appliances. Thevibrations from them may êtregênantes; they are the source of somenoise radiated by this machine and are therefore undesirable forusers, they can be transmitted to neighboring structures andaccelerate deterioration or aging, can also damage the rotatingmachines-they mêmes.il is therefore of interest to develop methodsto reduce the vibration level of the machines, as well as that of theirenvironment direct.Ces optimization methods (minimization) canminimize the natural vibrations using against vibration generatedby actuators requiring external power. The objective of this work isto develop a method of minimizing vibrations of a rotating machine,which aims to reduce the vibrational level of an area of its outercasing. This field can then be used for attachment of this machineand so help to minimize the amount of vibration it transmits to itsdirect environment. A new method also converge to the globaloptimum (minimum vibration value), and take into account possiblevariations of vibrational disturbances to eliminate. It allows asignificant reduction of vibrations, without changing thecharacteristics of the system. Voir les détails

Mots clés : Rotating machines, vibration sensors, optimization.

NDT CHARACTERIZATION OF NANOCOMPOSITE

A.Younes, N.Dilmi, A.BOUAMER, H.Amar, Z.GUEZOUI, M.amir, M.Zergoug  (2016)
Article de conférence

Nanostructured materials are current topics in research and development in recent years because of the good mechanical and physical properties compared to crystalline materials. The nanocrystalline coatings may show increased hardness, good mechanical strength [1], good corrosion resistance and the oxidation resistance, and / or good behavior to friction and wear [1,2]. In particular, nanostructured materials have good properties in tribology, motor vehicles, heavy machines and cutting tools, etc. that require advanced materials functioning with minimum energy loss. Nanostructured coatings such tribological surfaces for use in contact with harsh conditions were searched intensively for the past decade. PVD and CVD are well-known methods for depositing such [3] coatings. However, the drawbacks associated such that the deposition sector size, substrate geometry, cost and complexity of the process often limit their use. In this perspective, the deposit by thermal spraying gives much attention. The different materials Metal, ceramics or cermet [4], nanostructured coatings were deposited by thermal spraying processes such as HVOF. In addition, the properties of these coatings have been found to strongly depend on the porosity, of the phase distribution, and the residual stress [5-6]. Voir les détails

Mots clés : Nanostructured materials, alumina, Mechanical Alloying, MEB, EDX, DRX, VSM

Microstructure and Mechanical Behavior in Dissimilar SAF2205/API X52 Welded Pipes

Brahim BELKESSA, Djamel Miroud, Naima Ouali, Billel CHENITI  (2016)
Publication

The welding of a duplex stainless steel SAF 2205 DSS (UNS 31803) and high strength low alloy steel API X52by shielded metal arc welding process was conducted using two different filler metals, the duplex E2209 and austeniticE309 grade. The microstructures of the dissimilar metal joints have been investigated by optical microscopy, scanningelectron microscopy, energy-dispersive spectroscopy (EDS) and X-ray diffraction. EDS analysis at the interface X52 weldmetal showed an evident gradient variation of Cr and Ni between boundaries of fusion and type II, where the highesthardness value was recorded. Tensile strength and toughness values of the weld metal produced by E309 electrode areslightly higher than those of the weld metal produced by E2209 electrode. Potentiodynamic polarization tests of differentregions of the welded joints evaluated in 3.5% NaCl solution exhibit a high corrosion resistance of both weld metals. Voir les détails

Mots clés : Dissimilar metals welding, 2205 Duplex stainless steel, API X52 HSLA steel, Heat affected zone, mechanical properties

Mechanical and Metallurgical Characterization of HSLA X70Welded Pipeline Steel Subjected to Successive Repairs

Bouzid MAAMACHE, Mabrouk BOUABDALLAH, Abdelhalim Brahimi, Youcef Yahmi, Billel CHENITI, Brahim MEHDI  (2016)
Publication

The aim of this work is to study the influence of successive weld repairs on the microstructure and themechanical behavior of the heat-affected zone (HAZ) of an HSLA X70 steel. Detailed microstructural examinationcombined to grain size measurement showed that beyond the second weld repair, the microstructure of the HAZ undergoessignificant change in the grain morphology and grain growth. The results of the X-ray diffraction analyzed using MAUDsoftware indicated an increase in the crystallite size and a decrease in the dislocation density according to the number ofweld repair operations. Consequently, a loss of mechanical properties, namely the yield strength and the toughness with thenumber of weld repairs, was recorded. Beyond the second weld repair operation, the properties of the welded joint do notfulfill the standards applied in piping industry. Voir les détails

Mots clés : HSLA X70 steel; Successive weld repair; Heat affected zone; Dislocation density