Investigation on brittle fracture mechanism of a grade E cast steel knuckle

A paper published on « Case Studies in Ingineering Failure Analysis », on april 2014.

This paper investigated the brittle fracture mechanism of a grade E cast steel knuckle that is one of the key components of the coupler for railway wagon. The fracture morphology mainly shows the characteristic of cleavage, quasi-cleavage fracture as well as a little ductile fracture, so the failure of the knuckle can be attributed to brittle fracture distinctly. Moreover, a welding repair area with high hardness is also found in the fracture region, which might initiate micro-cracks on the surface of the knuckle. As a result, it can be inferred that under an impact load that did not exceed material fracture limit, the micro-cracks initiated from weld repair zone propagated rapidly into the inner matrix by continuously fracturing the dendrites along shrinkage porosity regions until the knuckle failed instantly.

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Défaillances des installations, application aux équipements sous pression : jeudi 16 novembre à Lyon

Mis en avant

Journée TechniqueLes équipements sous pression sont soumis à de nombreuses sollicitations et leurs endommagements peuvent avoir des conséquences graves avec des impacts humain, industriel ou environnemental.

Différents outils sont aujourd’hui à notre disposition pour analyser ces dommages et aboutir au bon diagnostic. Ils nous guident également pour définir les actions préventives ou curatives à apporter pour autoriser la poursuite de l’exploitation de ces équipements.

Les spécialistes de l’analyse de défaillances au Cetim, régulièrement confrontés à ce genre de problématiques, vous feront part de leur expérience en s’appuyant sur des cas concrets.

Pour connaître le programme de la journée et s’inscrire : cliquez ici

Formation – Analyse de défaillances : engrenages et roulements – En Novembre à Mulhouse

Mis en avant

Comprenez les causes des défaillances de vos engrenages et roulements pour mieux les éviter. Mettez en œuvre des actions correctives appropriées en utilisant une démarche structurée d’analyse d’avaries.

Plus qu’une session en 2017 :

  • Mulhouse du 16/11/2017 au 17/11/2017

Plus d’informations et inscription

The Challenger Disaster Report

In this essay, we will make a thorough study of the technical and administrative factors that contributed to the failure of the Shuttle Challenger project. Starting from paying attention from the planning stage, the implementation of the project, and even the consequences and further investigations, to be able to identify the lessons to be learned in both areas. It is expected that by completing this task, we can notice the critical factors that we need to pay particular attention to approaching ourselves as students that can develop projects successfully.

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Pitting corrosion failure analysis of a wet gas pipeline

This paper, published on Engineering Failure Analysis, august 2017, présents corrosion failure analysis of an underground natural gas pipeline. The pipeline material grade is API 5L X65 with 10-in ID. The pipeline transfers multiphase fluid (gas, condensate, and water) from a gas well to a gas gathering plant, located 4200 m away from the well site. A portion of the line failed due to pitting corrosion under unknown circumstances. Based on visual and microscopic analyses and reviewing the background information, the following pitting corrosion sequences were identified: the oversized pipeline changed the dominant flow regime to “stratified”. In the stratified flow regime, the accompanying water phase accumulated in the pipelines’ low points. Considerable concentration of calcium ions along with high pH in CO2 media favored precipitation of calcium carbonate. The relatively thick scales adhered to the pipe surface were partially loosened and removed by the regional turbulent flow. This exposed the fresh steel surface to the corrosive media. The uncovered areas acted as the preferential anodic sites coupled with nearby large cathodic sites which were covered by scales and/or corrosion products. Under such conditions, pits emerged on the steel surface until one of them grew faster and failed the gas pipeline.

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The Effects of Fiber Orientation and Volume Fraction of Fiber on Mechanical Properties of Additively Manufactured Composite Material

A thesis published by Conerstone : A Collection of Scholarly and Creative Works for Minnesota State University, Mankato.

Additive manufacturing (AM) also known as 3D printing has tremendous advancements in récent days with a vast number of applications in industrial, automotive, architecture, consumer projects, fashion, toys, food, art, etc. Composite materials are widely used in structures with weight as a critical factor especially in aerospace industry. Recently, additive manufacturing technology, a rapidly growing innovative technology, has gained lot of importance in making composite materials. The properties of composite materials depend upon the properties of constituent’s matrix and fiber. There is lot of research on effect of fiber orientation on mechanical properties of composite materials made using conventional manufacturing methods. It will be interesting and relevant to study the relationship between the fiber orientation and fiber volume with mechanical properties of additively manufactured composite materials. This thesis work presents experimental investigation of mechanical behavior like tensile strength and fatigue life with variation in fiber orientation and fiber volume fraction of 3D printed composite materials. The aim is to study the best combination of volume fraction of fiber and fiber orientation that has better fatigue strength for additive manufactured composite materials. Using this study, they can decide the type of orientation and volume percent for desired properties. This study also finds the range of fatigue limits of 3d printed composite materials .

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Numerical analysis of impact failure of automotive laminated glass: A review

An interesting article about failure analysis of impact on glass laminated, published on « Composites Part B »,april 2017.

Laminated glass is a simple sandwiched composite structure, while being widely used in the automotive industry as windshield glazings. It is considered to be safety glass due to its excellent performance in absorbing impact energy and bonding glass fragments. Meanwhile, the impact failure patterns of an automotive windshield glazing contribute to the traffic accident reconstruction. In recent decades, a growing interest has been devoted to the impact failure analysis of automotive laminated glass by means of numerical simulations. The purpose of this work is to present a comprehensive review concerning this aspect. We start by introducing six numerical algorithms for the modeling of the principal damage pattern, glass-ply cracking, followed by the introduction of material models for the plastic interlayer, PVB, and then address three numerical techniques for the adhesion modeling. Three kinds of laminated glass models are summarized. Finally, the performance of the numerical algorithms on the impact failure analysis of laminated glass in terms of glass-ply cracking and acceleration history is thoroughly discussed.

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Erosion of glass fibre reinforced époxy composites

An article published on the JOURNAL OF THE EGYPTIAN SOCIETY OF TRIBOLOGY (VOLUME 14, No. 2, April 2017).

Sand erosion of epoxy resin reinforced by randomly distributed glass fibres and filled by synthetic, paraffin and glycerine oils is studied. The effect of inclination of impact angle and oil content contained in the matrix of epoxy resin is investigated. In addition, the electrostatic charge generated on the eroded surface is measured. Reinforced epoxy demonstrates low erosion resistance compared to unreinforced epoxy. SEM surface examination reveals the effect of inclination angle on wear. Specimens filled by oil lose the electrostatic charge generated from sand erosion in earlier time compared to the unfilled test specimen.

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Se former aux contrôles non destructifs

Douze collaborateurs de Cryostar ont acquis les connaissances de base en matière de contrôles non destructifs. Pour cela Cryostar s’est adressé au Cetim-Cermat de Mulhouse, centre associé au Cetim. Ils sont aujourd’hui capables de choisir le contrôle adapté à la pièce et au défaut à détecter. Ils savent aussi… dialoguer avec un expert. telecharger le doc

La rupture en service des assemblages vissés

Les experts en analyse de défaillances du Cetim ont réalisé courant 1988 une étude statistique de 139 cas de ruptures d’assemblages vissés. Les résultats ont montré que pour les deux tiers des cas traités, 53 % des cas de rupture est dû à un phénomène de fissuration progressive et 47 % correspond à des ruptures brutales. Pour le tiers restant, plusieurs causes  conjuguées étaient à l’origine des défaillances.

Des dizaines de milliers de cas ont été traités ces quarante dernières années par le Cetim. Cette expérience fait du Centre une référence dans le domaine à même d’intervenir dans tous les secteurs d’activités. Avec aujourd’hui avec ses centres associés et partenaires, l’Institut technologique Cetim met un ensemble de compétences et de moyens au service des industriels et experts pour analyser, comprendre et proposer des solutions permettant d’éviter la reproduction de ces défaillances..

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