CRTI Library

Probabilistic analysis of corroded pipeline under localizedcorrosion defects based on the intelligent inspection tool

A methodology is developed in this paper to estimate the time-dependent reliability of a pipeline in Algeria, which is in exploitation from 1981 and with internal and external localized corrosiondefects detected in 2009. A probabilistic approach was applied to a pipeline made of API 5L X60steel for the long-distance transportation of natural gas (55 km), which crossing several geographical reliefs in different country areas. The analysis was carried out by taking into consideration the potential stochastic variables altering drastically the reliability of the pipeline, i.e.,dimensions of the localized corrosion defects, their locations, and distribution, and the corrosionrate. The correlations between the pipeline spatial corrosion defects distribution and their dimensions, obtained by using an intelligent inspection tool are used to analyze the actual inservice corrosion attack rate and for enhancement of the accuracy of the reliability assessment.The failure scenario was considered as the moment when the pipeline operating pressure exceedsthe failure pressure defined analytically in accordance with different commonly used standards.The assessment of the reliability index of the corroded pipeline subjected to internal pressure andthe failure probability was done. The detailed reliability analysis is carried out by using thesecond order reliability method (SORM) for the basic random variables with different probabilistic density within a nonlinear limit state function. The latter is based on the limit analysis ofthe failure pressure model for different standards and the numerical analysis using the finiteelement method and ANSYS software. Voir les détails

Mots clés : Reliability, corrosion, Inspection, FEM

Effect of Heat Treatment on the Structure, Wear and Corrosionof AISI L6 Tool Steel

This work is a contribution in analyzing structure, tribological behavior and corrosion ofAISI L6 hardened tool steel. Structural characterization and tribological behavior of steel wereinvestigated using Optical Microscopy (OM), Scanning electron microscopy (SEM), wear testing byfriction on a pin-on-disc Tribometer and corrosion by potentiodynamic polarization. Comparing tothe as-received steel, hardening has generated a fine martensitic microstructure causing a 1.5 timeshardness increase. Hardening has contributed to improvement of wear resistance as the coefficient offriction has decreased from 0.86 to 0.67μ. An increase in corrosion resistance was observed afterhardening treatment. Voir les détails

Mots clés : tool steel, AISI L6, friction, hardening, corrosion, heat treatment, wear

Study of the Bioactivity of Hydroxyapatite Elaborated

This work presents a study on the elaboration and characterization of Hydroxyapatite obtained from bovine bone calcined at 900°C for 3 hours with a particle size of around 125 μm and sintered at 1100°C. A prepared biological solution (Simulated Body Fluid, SBF), to study the biological response of our elaborated powder.We carried out a characterization by scanning electron microscopy (SEM) in order to observe the formation of the apatite layer during the immersion time. Voir les détails

Mots clés : hydroxyapatite, SBF, Biological response, Osteoconductivity

Microstructural and Mechanical Properties of Welding and Thermal Spraying Coatings on Ductile Cast Iron

The subject of this work is to evaluate the influence and adhesion degree of different coating layers deposited on a ductile cast iron substrate by two different methods, thermal spraying and welding with and without use of an interlayer. Microstructures of different zones and interfaces of coated specimens are investigated using optical microscope and scanning electron microscope SEM. Also, the mechanical behavior was evaluated by tensile test. It is found that when stainless steel thermal spraying coating onto the ductile cast iron substrate, the use of the nickel-based interlayer Ni allowed us to mitigate the disadvantages of cracking at the interface. This is due to the mechanical effect of nickel plasticity. In the case of coating by welding, the use of nickel-based buttering ENi-CI allowed us to reduce the diffusion of graphite to stainless steel, resulting in a reduction in the formation of harder alloy carbides. Finally, the mechanicals tests in particular the tensile test shows that the coating by welding is effective but causes a structural hardening; on the other hand the coating realized by thermal spraying does not really present sufficient adhesion. Voir les détails

Mots clés : Ductile Cast Iron, mechanical properties, microstructure, Thermal Spraying, Welding Coating

Caractérisation des paramètres de fissuration en mode d'ouverture par corrélation d'images et éléments finis d’un alliage d’aluminium 2xxx

In this work, a problem of fracture and crack resistance is studied, the 2000 aluminum alloy series available in market is chosen, in this context of fracture mechanics the structural durability and integrity of materials is investigated. Couple techniques are used, an experimental characterization assisted by the digital image correlation technique and finite elements based numerical simulations, the aim is to study the mechanical behavior in presence of cracks and determine the fracture toughness. Making use of theoretical notions, analytical formulas, experimental tests coupled by the recent digital image correlation technique and numerical simulations constitute an efficient protocol to characterize materials to resist against cracks. At the end of our work, the study was done to know the crack propagation in opening mode (mode I) and the stress evolution on the crack paths by the X-FEM extended finite element method. Voir les détails

Mots clés : failure in mode 1, stress intensity factor (SIF), Cracking, Correlation of digital images (CDI), FEM finite elements, Abaqus, Integral J, Extended finite element method (XFEM)

Caractérisation et modélisation numérique d’un composite époxy/Alfa.

Nowdays, natural fiber composites are increasingly getting great interest on an industrial scale. This undeniable success is linked to the intrinsic properties of natural fibers reinforcements and to their ecological character. Our study consists in characterizing the mechanical properties in tensile, bending and ultrasonic as well as morphological characterization by optical and scanning electron microscopy in order to evaluate their aptitude to replace synthetic fiber composites. The material to be characterized is composed of an epoxy matrix reinforced with 20% in weight Alfa short fibers. Numerical modeling using the finite element method allowed us to predict the Young's modulus of our randomly reinforced biocomposites. The ANSYS modeling software was used to generate the 3D representative elementary volume and to calculate the Young's modulus of the composite. The experimental results recorded are close to those obtained by numerical modeling. The latter remains therefore the goal to reach. Voir les détails

Mots clés : natural fibers, Alfa fibers, biocomposites, mechanical characterization, numerical modeling, ecology

DETERMINATION DES PROPRIETES ELASTIQUES PAR LES ESSAISDE TRACTION ET D’ULTRASON DE L’ALLIAGE EUTECTIQE AlSi13

Aluminum has very low mechanical properties. To significantly increase them, we actedon three main modifying factors of the microstructure. Addition to aluminum of a very lowdensity element including 13% silicon which facilitates the flowability of the metal, gravitysand molding and structural hardening treatments.Al-Si alloys are highly indicated by their lightness, their high tensile and corrosionresistance. The study focuses on the influence of maturation on the evolution of the elasticproperties determined by the tensile and ultrasound tests of the Al-13% mass eutectic alloy. Iffor six states: raw casting noted - F and maturation in 6h steps noted - M0h, M6h, M12h,M18h and M24h. The parts produced from this alloy are part of the components used invarious projects by SNVI Rouïba and Electro-Industries de Fréha (covers, pump casing,motor pistons, etc.).All the results of the mechanical and structural properties gathered in Part III of our thesisshow us that we should recommend for the molding of parts whatever the series: the grossreference state designated - F. Voir les détails

Mots clés : Al-Si, sand, ripening, mechanical properties

Effet des traitements thermiques sur le comportement microstructural et mécanique de l’acier inoxydable Lean duplex 2101 lors du vieillissement

As part of this project of memory we propose by this work a study on the microstructural and mechanical behavior of a stainless steel Lean Duplex LDSS 2101 during heat treatments realized in two stages: a treatment of dissolution at a temperature of 1050 ° C for one hour then water quenching, followed by an aging treatment at 720 ° C at different holding times (T = 10min, 60min, 10h, 24h, 120h, 240h) followed by quenching to water.The different samples are metallurgically characterized by optical microscopy and scanning electron microscopy (SEM). XRD analysis was used to identify the phases and precipitates formed during the treatments. Thermal treatments have significantly affected the phase equilibrium of stainless steel, caused by nitrides and carbides precipitation phenomena.Micromechanical characterization was performed by nano-indentation tests for the measurement of hardness and Young's modulus for each phase for the different samples. Voir les détails

Mots clés : stainless steel Lean Duplex LDSS 2101

Influence de l’énergie de soudage sur la microstructure et la résistance à la corrosion de l’acier inoxydable Lean duplex UNS S32101

Duplex stainless steels are widely used in industry, because their two-phase structure with equivalent fractions in austenite and ferrite gives them very interesting mechanical properties and high resistance to different types of corrosion. However, the use of these steels is limited by their sensitivity to the formation of hazardous intermetallic phases with adverse effects on hardness and corrosion resistance. It is a weakening of the material that is visible under certain welding conditions. The subject deals with the study of a welding process applied Lean duplex stainless steel, LDX 2101 to a nickel-reduced stainless steel and aims to show the influence of the experimental parameters (03 energies) on the microstructural and stress corrosion resistance properties ( CSC) of the weld joint Voir les détails

Mots clés : Lean duplex stainless steel, LDX 2101, welding energy, stress corrosion cracking (SCC)

Optimization of the number of layers for a fixed thickness of a composite material subjected to compression loading

In this paper, the effect of varying the number of layers for a fixed total thickness is investigated. In order to conserve the integrity and the safety of a multilayers composite structure, the search of the optimal number of layers in the cross section, induced the low stress-strain field intensity, is strongly recommended. Meanwhile, this study aims to show how the mechanical response of a multilayers composite plate loaded on a compression in the axial direction, changes when the number of layers increases from for a fixed total thickness. Voir les détails

Mots clés : security factor, stress-strain field, Composite material, Compression loading