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

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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Failure Analysis of Air Cooled Condenser Gearbox

A new article in « Case Studies in Engineering Failure Analysis » published on Sciencedirect.com.

Gears are very reliable components and normally work 5 to 6 years without failure.

This article is a case study of failure analysis of a gearbox which was failed in three months after its installation. The problem was identified by maintenance engineers through vibration monitoring of gearbox.

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Surface Contact Fatigue Failure of a Case Hardened Pinion Shaft

Piqure dentureAn article published in « Materials Research« , april 2014.

An investigation was made to determine the causes of surface contact fatigue failure of a case hardened driver pinion located in the intermediate shaft of a reducer gearbox used in a sugar and alcohol mill. The examination of the component revealed the presence of a cemented layer substantially thicker than that generally specified for pinions devised for this application.

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Cas concrets – Les défaillances touchent tous les domaines d’activité

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Six fiches d’analyse de défaillance publiées en 1975 dans Cetim-information sont mises à votre disposition dans la Mecatech.

Des dizaines de milliers de cas de défaillances ont été traités ces quarante dernières années par le Cetim.  Les quelques 110 fiches de cette série « Cas concrets » sont issues d’articles publiés dans la revue Cetim-Informations dans les années 1974 à 1990. Bien que ces fiches traitant de cas concrets soient anciennes, leur contenu est toujours d’actualité…

Cette expérience fait du Centre une référence dans le domaine, à même d’intervenir dans tous les secteurs d’activités. Avec aujourd’hui 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.

Failures of cranes due to wind induced vibrations

An interesting paper in « Engineering Failure Analysis »published on ScienceDirect.com.

Two different crane types suffered severe wind induced vibrations of tension bars for the counter weights during standstill periods. The vibrations led to fatigue fractures of tensions bars followed by collapses of the cranes. The parameters of wind speed and angle for the tension bar profiles were identified conducting comparative wind tunnel experiments. Recommendations for identification and prevention of wind induced galloping vibrations of tension bars were developed.

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A failure study of the railway rail serviced for heavy cargo trains

An interesting paper published in Case Studies in Engineering Failure Analysis, Volume 1, Issue 4, October 2013.1-s2.0-S2213290213000461-gr2

In this case study, a failed railway rail which was used for heavy cargo trains was investigated in order to find out its root cause. The crack is supposed to be initiated from the weaker ferrite networks. Given all of that, the failed railway rail is considered to be caused by overload. It is of great importance to improve the welding technology, and control the load of train in order to prevent similar failure in future.

Source : A failure study of the railway rail serviced for heavy cargo trains

Handling abuse causes premature bearing failures

An article published in « Case Studies in Engineering Failure Analysis » .

A bearing, can fail prematurely due to a variety of factors like wrong choice of a design for the application, lack of or inadequate lubrication, impact loads, vibrations, environmental factors like operating temperature, corrosive media, moisture, dirt or handling abuse during transport, mounting, reinstallation and servicing.

Two case studies are presented here wherein abusive handling likely caused premature fatigue failure of ball bearings.

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Adapter les dentures aux déformations

Suite aux pannes à répétition sur la ligne de propulsion d’un navire d’exploration pétrolière de la CGG, le Cetim en a identifié les causes et fourni les éléments pour y remédier en gardant le bateau en exploitation.

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Le Cetim est le leader français de l’analyse de défaillances et de l’expertise mécanique. Sa démarche, globale et multicompétences, traite la défaillance depuis ses origines jusqu’à la mise en place de solutions concrètes. 1 000 nouveaux cas sont traités chaque année.