Archives du mot-clef analyse de défaillance

Fractography of a neck failure in a double-modular hip implant

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2017-02-23_09h32_35An article published in « Case Studies in Engineering Failure Analysis« , 2014.

The tapered joints of modular hip implants are prone to fretting and crevice-corrosion. This can lead to total failure in under a year, especially for heavier, more active implant recipients. In this study, fractography of a failed Profemur Z implant showed that a life limiting fatigue crack was nucleated on the anterolateral surface of the implant’s neck. The fatigue crack nucleation area appeared to have both more fretting damage and a higher corrosion rate than on other surfaces of the neck.

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Failure analysis of a nose landing gear fork

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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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Comportement en fatigue des matériaux métalliques. Généralités

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2017-01-19_09h01_01L’édition de la collection Fatigue est issue de la révision de l’ouvrage de référence « Données technologiques sur la fatigue » publié au début des années 1980 par le Cetim. L’objectif de cette collection, composée à terme d’une dizaine de fascicules, est de délivrer à tout un chacun un état de l’art dans le domaine de la fatigue appliqué à tous les domaines et de se placer dans un contexte de capitalisation des connaissances. Cet ouvrage de la collection Performances du Cetim (9Q238) « Comportement en fatigue des matériaux métalliques – Généralités » correspond au premier de ces fascicules. Il traite notamment des mécanismes et des faciès de rupture par fatigue, du chargement et des notations, de la fatigue à grand nombre de cycles, de la fatigue plastique ou oligocyclique, etc. Un ensemble d’éléments permettant d’appréhender ce phénomène de fatigue responsable de la majorité des ruptures en service de pièces ou de structures dans l’industrie.

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Fatigue cracking of high pressure oil tube

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1-s2-0-s2213290213000321-gr1An article about a Case study of failure analysis published in « Case Studies in Engineering Failure Analysis« , July 2013.

A high pressure oil tube with nominal diameter 50.8 mm and nominal thickness 4 mm has prematurely failed with a longitudinal crack. The failure was detected after 11 months of operation. The tube is part of the hydraulic power unit of an off shore oil and gas platform. The maximum designed internal pressure was 20 MPa and the service temperature was 25 °C with no significant variation. In practice, the internal pressure varies from 16 to 20 MPa under operation, and shutdowns rarely occur.

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Failure analysis of Rocker liner used as a charging system of blast furnace

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2016-12-08_10h04_01      2016-12-08_10h05_28

An article published in « Case Studies in Engineering Failure Analysis« , July 2013.

In this study, failure analysis of rocker liners used for charging system of blast furnace was carried out. The failed rocker liner samples shows non-uniform distribution of carbides, resulted in variation of hardness as well as wear properties. In the case of failed sample, the reason for the poor wear resistance of the component was due to the non-uniform carbide in pearlitic matrix.

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Sulfide stress corrosion cracking and hydrogen induced cracking

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1-s2-0-s2213290213000424-gr11-s2-0-s2213290213000424-gr2

A case study published in « Case Studies in Engineering Failure Analysis » on www.sciencedirect.com.

The wellhead flow control valve bodies which are the focal point of this failure case study were installed in some of the upstream facilities of Khangiran’s sour gas wells. These valve bodies have been operating satisfactorily for 3 years in wet H2S environment before some pits and cracks were detected in all of them during the periodical technical inspections. During investigation many cracks were observed on the inner surface of the valve body grown from the surface pits. The results indicate that flow control valve body failed due to combination of hydrogen induced corrosion cracking (HICC) and sulfide stress corrosion cracking (SSCC). According to HIC and SSC laboratory tests and also with regard to cost of engineering materials, it was evident that the best alternative for the valve body alloy is A217-WC9 cast Cr–Mo steel.

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Failure analysis of tube-to-tubesheet welded joints in a shell-tube heat exchanger

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An article in progress in « Case Studies in Engineering Failure Analysis », Volume 7 (october 2016).

In this work, fracture failure of a shell-tube heat exchanger at the tube-to-tubesheet welded joints was investigated. Fatigue started at initial defects of the welded joint was confirmed as the failure mechanism of the heat exchanger. Bad welding and unsuitable expansion gave rise to the formation of initial cracks. The alternating stress comes from various reasons such as the resonant vibration.

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Perforated mechanism of a water line outlet tee pipe

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tuyauAn article published in « Case Studies in Engineering Failure Analysis« , Volume 4, October 2015.

A corroded tee pipe belonging to a 10-in new separator water line outlet installed in an offshore oil well drilling rig was investigated. The configuration of the large corroded pit had the shape of an imperfect horse’s hoof with a completely corroded interior and a honeycomb-like cavity. There is a badly corroded pit at the welded seam at the joint connecting the tee pipe and flange. The penetrating puncture hole at the turn of the tee pipe is likely the result of cavitation erosion accompanied by chemical/electrochemical corrosion, and the corrosion on the seam connecting the tee pipe and flange is likely the result of electrochemical corrosion.

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Stress corrosion cracking of full sized rockbolts

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2016-06-04_07h48_16An article published in  « International Journal of Rock Mechanics & Mining Sciences – 81 (2016)« .

Previous studies had identified that a testing protocol was required to examine stress corrosion cracking (SCC) of full sized rockbolts under simulated in situ conditions. It was found that SSR testing provided an appropriate analogue for examining rockbolt susceptibility to SCC and was thus used to examine the effect of grit blasting, galvanising and varying steel grades on the SCC resilience of rockbolts. Of these, 300 grade steel and galvanising provided the most promising resistance to SSC, while grit blasting provided a 40% improvement in resistance compared to untreated HSAC 840 grade rockbolts.

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