Archives mensuelles : novembre 2013

Assessment of a gouge and dent defect in a pipeline

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This paper pubished in Engineering Failure Analysis, deals with A37 steel pipelines containing a gouge and dent defect. The influence of the dent depth on the burst pressure of pipelines is evaluated for a given geometry of the gouge. Experimental burst tests are performed and finite element analysis is used in order to compare the numerical and experimental results. Experimental results showed that a combined gouge and dent defect does not reduce the burst pressure of A37 steel pipelines. These results contradict established research conclusions and the bulk of the literature on the subject. A combined criterion based on volumetric method and stress triaxiality is proposed for assessment of pipelines containing a gouge and dent defect.

Analysis of notch effect in the apparent fracture toughness and fracture micromechanisms

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This paper, reported by Sciencedirect.com, presents an analysis of the notch effect on two ferritic-pearlitic steels operating within their corresponding lower shelf, and develops an experimental programme, composed of 28 CT characterisation specimens and 72 CT validation specimens, together with finite elements analysis with the aim of validating the apparent fracture toughness predictions provided by the Theory of Critical Distances. The results have shown how this theory provides reasonable predictions of the apparent fracture toughness of the material .

The research is completed with the analysis of the evolution of fracture micromechanisms when the notch radius increases, revealing a direct relation between this evolution and the apparent fracture toughness observations.

Failure analysis of a martensitic stainless steel roll

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Sciencedirect.com report an article published in « Engineering Failure Analysis » : the failure analysis of a martensitic stainless steel (CA-15M) roll manufactured by centrifugal casting and used in cast glass rolling was carried out. The crack propagation began in the internal surface of the roll. Tensile thermal stresses in the internal surface of the roll associated with microstructural embrittlement (network of interfacial carbide and porosities) are thought to be the main causes for the premature failure of the roll. Finally, materials selection was performed to replace the CA-15M stainless steel with another class of stainless steel for centrifugal casting.

Fragilisation par le zinc liquide des aciers haute resistance

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MATEC Web of Conferences signale une étude présentant les investigations menées sur la fragilisation par le zinc liquide d’un acier électro-zingué. Elle a permis de caractériser la perte de ductilité en traction d’un acier galvanise causée par la FML (fragilisation par les Métaux Liquides). Le lien entre fragilisation, mouillage intergranulaire et propagation de fissure a été établi.

Cette étude a été présentée lors des journées annuelles de la SF2M 2013, les 29-31 octobre 2013, à l’ Ecole Centrale de Lille.

Failure analysis techniques for a 3D world

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The proliferation of advanced IC package configurations is driving the need for new tool failure analysis (FA) tool development. Although scientists and engineers in the semiconductor industry developed new tools and techniques based on Moore’s Law, with its need to analyze ever-smaller devices, the advent of three-dimensional packaging schemes requires new tools. In this paper they quickly review the existing tools used for package-level FA and introduce several new techniques that aid with this type of analysis. They also discuss the problems and challenges moving forward for this type of tool development.

Cracking of an austenitic stainless steel lance pipe

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Kiln of a lime plant, a part of an integrated steel plant, converts limestone (CaCO3) into lime (CaO) by heating at a temperature of around 900 °C using coke oven gas as a fuel. Coke oven gas is a by-product of the coke plant, which contains mainly hydro-carbons. The coke oven gas is lanced into the kiln through a number of pipes attached to the kiln. The lance pipes are cracking prematurely within 6 months of their service against an expected service life of 3 years.  The analysis of cracking of the lance pipe is presented in this article. It will be published in Engineering Failure Analysis in December 2013.

More information at : Cracking of an austenitic stainless steel lance pipe in a lime calcining plant.

Delamination and discoloration of photovoltaic module

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Discoloration and delamination (D&D) of encapsulant in a photovoltaic (PV) module affect the electrical characteristics. Therefore, in this study D&D-induced degradations are investigated with a 25-year-old PV module. The average power output of 25-year-old PV modules decreased by 17.9% compared to initial value. However, insulation properties have been stable over 25 years. Electroluminescence image shows that discoloration has an effect on the cell degradation. The effect of D&D on the light reflectance and transmittance is evaluated by performing a trapezoidal integration with the standard global reference spectrum. Failure analysis reveals that delamination occurs at the interface between encapsulant and solar cell and also shows that corrosion of solder occurred near delamination site

More at :http://www.sciencedirect.com/science/article/pii/S0026271413002370?np=y

Il s’agit d’un article présenté au Symposium européen sur la fiabilité des Electron Devices, Physique et analyse de défaillance

Un cours sur la Mécanique de la rupture

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La mécanique de la rupture a été introduite par Griffith vers 1920. L’objectif de la mécanique de la rupture est de caractériser le comportement à la fissuration des structures à l’aide de paramètres quantifiables au sens de l’ingénieur, notamment le champ de contraintes, la taille de la fissure et la résistance à la fissuration du matériau.

J’ai trouvé ce cours de l’Ecole des Mines de Douai mis en ligne en octobre 2010, il vous montrera que la  compréhension des phénomènes physiques à la base des endommagements et de la rupture est fondamentale pour choisir les méthodes appropriées d’analyses de défaillances ou de dimensionnement de pièces mécaniques.