Archives du mot-clef case study

Failure analysis of interfering part of a steam turbine journal bearing

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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

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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

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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

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

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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

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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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Fatigue Failure Analysis of a Cooling Fan Blade

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A paper published in  » Engineering Failure Analysis » on www.sciencedirect.com.

Fatigue failure of holding U-bolt of a cooling fan blade is analyzed. Fractography of the fracture surface reveals the characteristics of a fatigue fracture. Finite element modeling is used for stress analyzing. Analysis of the loading conditions indicates that the bolts are under multiaxial fatigue. ……..

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Failure analysis of a bridge crane shaft

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

Failure analysis of a shaft used in a bridge crane has been carried out. The shaft fractured in the keyway with evidence of fatigue. The geometry of the keyway also promoted the initiation crack because the width and height were erroneously designed. It was concluded that all these factors produced fatigue failure.

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Brittle fracture of a grade E cast steel knuckle

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This paper was published in « Case Studies in Engineering Failure Analysis » on April 2014. It 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.

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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Analysis of abnormal fatigue failure of forklift forks

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A paper published in  » Engineering Failure Analysis » finded on ScienceDirect.com.

The analysis of an abnormal failure of forklift forks is presented in this work. The investigation results suggested that failure occurred due to fatigue mechanism followed by sudden overload fracture. The orientation of fatigue fracture indicates abnormal lifting operation, favouring crack initiation from outer fork area which is the compression designed zone. Moreover, various surface flaws and weakness areas (such as surface marks, decarburized microstructures and weld zones) identified on the outer fork zone, compromise fatigue strength inducing premature crack nucleation and fast growth towards final failure.

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Fatigue fracture of cutter blade made of high-speed steel

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An interesting  paper in « Case study in Engineering Failure Analysis » published on ScienceDirect.com. This paper presents the failure analysis of broken blade of the cutter Ku 500VX. The damage of the blade was caused by changes of the structure (formation of the brittle micro dendritic structure) that occurred during manual electric engraving process when the material was heated till its melting point. As a results the stresses occurred in surface what provided to micro cracking and to propagate the fatigue fracture. The origin of this fatigue fracture was in the place where the inscription was made.

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