Care and Maintenance of Bearings

Une publication intéressante chez SNR (NTN Corporation) qui présente les différents cas de défaillance pouvant affecter des roulements.

Pour accéder au document cliquez ici

Et si vous rencontrez un problème de défaillance de roulement n’hésitez pas à contacter les experts du Cetim.  En confiant votre expertise au Cetim, centre technique indépendant et neutre, vous êtes assuré d’une approche objective, compétente et factuelle.
Ses équipes dédiées pratiquent l’analyse des défaillance au quotidien et s’engagent sur des diagnostics.
Savoir pourquoi est son cœur de métier.
Savoir quoi faire est son atout, pour que vous tiriez de cet événement une nouvelle force de compétitivité !
Le Cetim est leader français en analyse de défaillances mécaniques, enrichi de son expérience de 30 ans, de 1000 nouveaux cas traités par an dans tous les domaines de la mécanique.

In vivo shell-like fractures of veneered-ZrO2 fixed dental prostheses

A non commum case study of failure analysis published in october 2014 in « Case Studies in Engineering Failure Analysis« .

Fractographic analyses are performed in two fixed dental prosthetic reconstructions made of ZrO2 frameworks covered by a veneering ceramic that fractured during function in the mouth. Internal thermal residual stresses and occlusal surface defects from localized contact overloading were found to precipitate the fracture in Case 1, whereas extreme occlusal surface damage from sliding chewing contact was determinant in the fracture of Case 2. The interface between the veneering ceramic and the ZrO2 framework was unaffected by the fractures.

Source : In vivo shell-like fractures of veneered-ZrO2 fixed dental prostheses

Grooving corrosion of seam welded oil pipelines

A paper published in « Case Studies in Engineering Failure Analysis« , october 2014.

24” pipeline carrying oil was failed in the form of longitudinal crack at the 6 O’clock position resulting in oil spill. The failed pipe was investigated to reveal the main cause of its failure. The procedure of investigation was built on studying the intact pipe, rupture area, parent material, and intact weld. Cracks were originated from weld defected sites, initiated by grooving corrosion, propagated by inertia at the normal designed pressure condition, and stopped when stress relief is attained.

Source : Grooving corrosion of seam welded oil pipelines

Weld failure analysis of 2205 duplex stainless steel nozzle

A publication in « Case Studies in Engineering Failure Analysiss, october 2014.

Failure analyses of weld joint between the nozzle and the head of the reactor made of 2205 duplex stainless steel was performed by optical microscopy (OM) and scanning electron microscopy (SEM). Cracks were found in HAZ of the weld. The depth of the cracks is equal to the thickness of the inner weld. Localized uneven distribution of ferrite/austenite with 80-90% ferrite in weld is found. Results show that the cracks occurred along columnar granular with cleavage fracture. Poor weld process probably results in these cracks.

Source : Case Studies in Engineering Failure Analysis

Failure analysis of interfering part of a steam turbine journal bearing

An article published in « Case Studies in Engineering Failure Analysis« , octobre 2014.

Journal bearings as so sensitive parts of steam turbines are very susceptible to failure through different mechanisms of wear, fatigue and crush during service conditions. Failure occurring through these mechanisms lead to turbine completely shut down as a result of interfering in working conditions of bearing different parts. In this paper, failed interfered part of a journal bearing related to a 320,000 kW steam turbine was examined. The studies were revealed that the bearing part loosing and inappropriate clearance can produce relative displacements under cyclic gradient loading. This condition was detrimental for the service life of turbine journal bearing via failure through fretting fatigue mechanism.

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Failure analysis of re-bars during bending operations

Failure_analysis_of_Rebar

An article published in « Case Studies in Engineering Failure Analysis« , october 2014.

This  paper highlights failure investigation of a failed rebar during bending operations. From fractography and microstructural analysis it is confirmed that the rebar sample failed in brittle manner due to through harden martensitic structure and which indicates that there is some anomaly in water box resulting in these premature failures.

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Cas Concrets – Des ruptures de fatigue en flexion

Avatar Cas ConcretsLe mode de sollicitation en service influe sur la morphologie des faciès de cassure. Les quatre cas de ruptures par fissuration progressive en fatigue en flexion plane et rotative illustrent ce propos. Ces quatre fiches d’analyse de défaillance avaient été publiées en 1981 et 1982 dans la revue Cetim-information. 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 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. Les différentes expertises de cette série « Cas concrets » sont issues d’articles publiés dans la revue Cetim Informations dans les années 74 à 90. Bien que ces fiches traitant de cas concrets soient anciennes, leur contenu est toujours d’actualité…

Source : Cas Concrets – Des ruptures de fatigue en flexion – Cetim – Centre technique des industries mécaniques

Concilier soudage et peinture, le 1er juin à Cherboug

Rendez-Vous de la MecaniqueQue mettre en œuvre pour fiabiliser la tenue de vos peintures ?

  • Améliorer la préparation de vos pièces,
  • Améliorer la qualité du soudage
  • Peinture : état des lieux

… pour des pièces fiables et esthétiques.

En savoir plus et s’inscrire

Abrasive Wear Failure Analysis of Tungsten Carbide Hard facing on Carbon Steel Blade

This content has been downloaded from IOPscience, Series: Materials Science and Engineering 165 (2017),

This study investigate the abrasive wear failure of tungsten carbide hardfacing on continuous digester (CD) blade (carbon steel) in an environment of sulphuric acid and ilmenite ore mixture. Comparison being made on the hardness, thickness and microstructural of the hardfacing between unworn and 3 months old worn blade on few locations around the blade. The cross sections of the blade revealed non-uniform coverage of the hardfacing on the blade for both worn and unworn blade. The edge of the blade has the least amount of hardfacing thickness which with time acts as the point of failure during the wear process. The hardness obtained from both the unworn and worn samples are around 25% lower from the hardfacing electrode manufacturer’s hardness specification. Microstructural micrograph analysis of the hardfacing reveale

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Concerns of corrosive effects with respect to lightning protection systems

An interesting  paper published in  » Engineering Failure Analysis » on www.sciencedirect.com, Volume 57, November 2015.

Lightning protection system elements need to be selected from materials which are resistant to corrosion and should be protected from fast degradation. However, over the time corrosion will take place in the presence of galvanically dissimilar metals in the same electrolyte (moisture)……

This paper presents the causes of corrosion and recent developments in minimising the corrosion associated with lightning protection and grounding systems.

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