Cas Concrets de défaillance de composants mécaniques

Avatar Cas ConcretsDes éléments de fixation corrodés en service, un mord retrouvé fissuré en stockage, un ressort de compression  rompu en fatigue. Quatre analyses de défaillances résumée sous forme de fiche. Ces quatre fiches d’analyse de défaillance ont été publiées il y a 25 ans dans la revue « Cetim-information », mais elles sont toujours d’actualité. Retrouvez les dans la Mécatech du Cetim.telecharger le doc

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Cas concrets – Ruptures de pièces de manutention-levage

Avatar Cas ConcretsUne série de quatre fiches d’analyses de défaillances de pièces mécaniques sont consultables en ligne dans la Mécatech. Elles concernent des pièces de manutention-levage.

Retrouvez dans la Mécatech les ré-éditions des fiches d’analyse de cas concrets que le Cetim a publié dans la revue Cetim-Informations dans les années 1974 à 1990. Bien qu’anciennes, le contenu de ces fiches est toujours d’actualité.

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Cas Concrets : ruptures brutales ou par fatigue d’arbres

Avatar Cas ConcretsArbres de transmission de couples ou axes de rotation, voici trois cas concrets d’analyse de ruptures d’arbres ayant des origines différentes : problème de matière, d’usinage, de sollicitations anormales.

Retrouvez dans la Mécatech les ré-éditions des fiches d’analyse de cas concrets que le Cetim a publié dans la revue Cetim-Informations dans les années 1974 à 1990. Bien qu’anciennes, le contenu de ces fiches est toujours d’actualité.

telecharger le doc

Crankshaft failure analysis

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

A case study of a crankshaft catastrophic failure of a motor vehicle and its failure analysis is presented. The crankshaft suffered a mechanical seizure on the crankpin no. 2 after 3 years in service. It was repaired and after 30,000 km the vehicle had a damage again, with a catastrophic failure on the same crankpin.

More at : Crankshaft failure analysis of a motor vehicle.

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

Understanding the Effects of Hydrogen on SCC of Pipelines

A thesis submitted in Department of Chemical and Materials Engineering University of Alberta, © Zeynab Shirband, 2016.

Near-neutral pH stress corrosion cracks (NNpH SCC) are developed under coating disbondments on the external surface of pipelines where the surface of pipeline is exposed to the soil solution. NNpH SCC initiation and early stage of growth is mainly governed by the dissolution process of steel. …This study aimed at understanding the contribution of these important factors to NNpH SCC. In this study, the role of coating disbondment on hydrogen ingress into pipeline steels and the effects of mill-scale and hydrotesting on NNpH SCC crack initiation are investigated.

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Failure analysis of a bridge crane shaft

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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Analysis of abnormal fatigue failure of forklift forks

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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Low hardness on bearing race

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

Presence of decarburization on rolled bar coupled with out of square forging can lead to the presence of decarburized layer on one of the faces of a bearing race. This decarburized layer gives rise to low hardness on the face of the race. A series of examinations including micro-structural and macroscopic examinations on the defective samples revealed out of square forging as a root cause for the presence of the decarburized layer on a part of the one of the faces of a bearing outer race. This paper brings out the detail of investigation carried out.

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Failure analysis of a nose landing gear fork

2017-02-02_09h26_14This paper presents a detailed analysis of a nose landing gear failure. The developed work comes following an accident occurred in which the nose of the landing gear’s fork of a light aircraft bent during landing. Nose gear failures are a high concern in the aviation industry. According to Federal Aviation Administration, in average 55% of aircraft failures occur during takeoff and landing while the remaining occurs during flight

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