Pour s’assurer de l’étanchéité des réservoirs de GNL du terminal méthanier de Dunkerque, la société Entrepose Contracting a choisi de procéder à un contrôle par émission acoustique.
La méthode de contrôle par émission acoustique mise en œuvre par le Cetim a permis de répondre à aux interrogations d’Entrepose Contractingdans un délai extrêmement court. Les tests ont été exécutés sur trois jours dans des conditions d’accès et climatiques difficiles. Soixante capteurs piézoélectriques positionnés tous les 5 m sur la périphérie du liner ont permis de localiser une zone problématique de faible dimension à la jonction d’un piquage d’une tubulure et du liner. À l’issue de l’investigation, la source du phénomène de bullage a été identifiée.
L’analyse de défaillance est un processus méthodique permettant un diagnostic efficace des causes des différents modes de défaillance: rupture, usure, corrosion. La connaissance des origines des avaries facilite la mise en œuvre d’actions correctives et préventives afin qu’elles ne se reproduisent pas.
Pour l’industriel, fabricant ou utilisateur, une défaillance a souvent de lourdes conséquences :
– arrêt de production et pertes d’exploitation,
– litiges commerciaux et baisse d’image de marque,
– accidents humains,
… donc des conséquences financières!
Ball bearings used inside the ISS Distillation Assembly centrifuge require superior corrosion and shock resistance to withstand acidic wastewater exposure and heavy spacecraft launch related loads. These requirements challenge conventional steel bearings and provide an ideal pathfinder application for 50-mm bore, deep-groove ball bearings made from the corrosion immune and highly elastic intermetallic material 60NiTi. During early ground testing in 2014 one 60NiTi bearing unexpectedly and catastrophically failed after operating for only 200 hr. A second bearing running on the same shaft was completely unaffected. An investigation into the root cause of the failure determined that an excessively tight press fit of the bearing outer race coupled with NiTi’s relatively low elastic modulus were key contributing factors. The proposed failure mode was successfully replicated by experiment. To further corroborate the root cause theory, a successful bearing life test using improved installation practices (selective fitting) was conducted. The results show that NiTi bearings are suitable for space applications provided that care is taken to accommodate their unique material characteristics.
L’Institut de Formation du Caoutchouc (IFOCA), basé à Vitry-sur-Seine (Val-de-Marne), a annoncé le lancement de deux nouvelles formations numériques.
Après le succès de sa première Formation en ligne ouverte à tous (Massive open online course ou MOOC), le centre de formation français aux caoutchoucs IFOCA vient de lancer deux sessions SPOC (Small private online course), des formations payantes abordant les thèmes suivants : Modélisation du comportement mécanique pour la simulation numérique et surtout Analyse de défaillance des pièces en caoutchouc.(…)
A case study published in « Case Studies in Engineering Failure Analysis » – April 2016.
In this study, the fracture failure of the 4Cr13 stainless steel linkage components in circuit breakers was studied. The microstructure and morphology of fracture surface were observed by scanning electron microscopy and optical microscopy. A micro-Vickers tester measured the hardness of the components. The tensile strength and strain of the components were determined by a universal testing machine. The results show that fracture failure mode was quasi-cleavage fracture, and some dimples and edges of cleavage were present on the fracture surface.
An article about a case study published in « Case Studies in Engineering Failure Analysis » – april 2016.
A temporary threadbar used for precast segmental construction broke during the post-tensioning stage before reaching the service load. Failure analysis showed that the premature failure of the bar was due to the presence of an arc strike. The arc strike effects on the material and threadbar integrity are considered.
An article published in the « International Journal of Engineering Science and Computing« , June 2016.
Spring steel is a prominent piece of material in industrial and automotive application. Hydrogen embrittlement (HE) is an inherent phenomenon, which will occur during the course of service life, at the same time it has to sustain a variety of loads acting on it. Among all the wear of spring steel plays a vital role. Hydrogen embrittlement leads for pre mature failure of the component. In view of this, an attempt was made in this experimental study to performance of hydrogen embrittled spring steel (EN-47 / SAE 6150/SUS 10) under the dry sliding condition. The specimen preparation and the experimentations have been carried out according to the ASTM standards. The experiments performed based on plan of taguchi technique. Cathodic charging is having been adopted for the embrittlement of the spring steel material. A known level of embrittlement has made, wear test has been carried out. Results have shown that, load and sliding distance is more pronounced on the wear of the embrittled spring steel material rather than speed.
A case study published in « Case Studies in Engineering Failure Analysis » – april 2016.
This paper investigates the failure of a rocker arm shaft of a passenger car. The shaft failed by brittle fracture across one of the four holes supporting the shaft into the cylinder head. The running distance of the engine just before failure was 40,626 km. These cracks may have been induced in the shaft by the non-uniform cooling during quenching in the course of heat treatment, or may be nucleated by repeated loading during service. This premature failure has occurred by the rapid crack propagation because of the lower fracture toughness of the martensite.
A paper find on the web about fatigue of Tidal Turbine Blade Composite Materials.
This has led to the emergence of tidal turbine designs often inspired from earlier developments in the wind turbine industry. Composite materials including Glass fibre reinforced polymers (GFRP) are a low-cost, low weight and corrosion resistant material for this application. Cyclic loading due to tidal flow and wave conditions is a common characteristic of tidal turbine devices and the good fatigue performance of composite materials means they are widely used, however limited information are available to predict material behaviour under coupled environmental and cyclic loading. This problem is addressed in this paper, by introducing a methodology for prediction of the fatigue behaviour of composite tidal turbine blades.