## Sciences des matériaux

#### NDT CHARACTERIZATION OF NANOCOMPOSITE

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

#### Acoustic Emission Monitoring of high risk installation in industrial environment

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

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

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 CO_{2} 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

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

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

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

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.

#### Estimation of ultrasonic wave parameters in materials under bending force

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

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

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

#### Temperature Effects on Thin film Based SPR-Sensor

In this paper, using the angle interrogation methods, we simulate the effect of temperature fluctuation on thin film based SPR-sensor. The sensor configuration is a three layer Krestchmann configuration consisting of glass prism, thin metallic layer, and bulk sensing layer. The temperature sensor uses RPS geometry of three interfaces where the refractive index of the layer adjacent to the environment is very sensitive to changes in the environmental temperature. The final results indicate that, as the temperature decreases, Θ_{min }(resonance angle) shift to larger angles and increased in R_{min} .These results can be used in the development of chemical, biomedical sensors, is suggestedVoir les détails

**Mots clés : **surface plasmon resonance (SPR), thermo-optic effect, temperature sensor.

#### Non intrusive stochastic finite elements method applied for non destructives NDT problems

The current work concerns the study of harmful defect detection for the inspected structure by eddy current non destructive testing. So a non intrusive stochastic finite element method was exploited in the case of 2D magnetodynamic equation. The electrical conductivity is considered as random variables and generated using Monte -Carlo method.Voir les détails

**Mots clés : **Stochastic finite element method, Eddy Current, Conducting plate, Random variable

#### Reconstitution of complex defects with the methodof neural network: Application for the nondestructiveevaluation

in this work, we propose a reconstitution of complex defects starting from the results obtained during a nondestructive testing by eddy currents carried out on aconducting plate by using the neural network. We provided tothe neural network the values of impedance of the differential sensor calculated using a modeling by finite elements.The values of impedance are injected at the input of the neural network and the depth of the defect is recovered in its output, we used the gradient of the error propagation algorithm for performing learning of the neural network.Voir les détails

**Mots clés : **Neural Network, eddy currents, impedance, complex defect, nondestruction evaluation