Un cas concret d’analyse de défaillance rapporté par ScienceDirect.com et publié dans « Case study in Engineering Failure Analysis ».
Un dommage du revêtement anti-corrosion associé à un processus de fatigue est responsable de cette défaillance.
Pour lire l’article cliquez ici
An interesting paper in « Case study in Engineering Failure Analysis » published on ScienceDirect.com. This paper analyzed why a compression coil spring fractured at the transition position from the bearing coil to the first active coil in service, while the nominal stress here should always be much less than that at the inside coil position of a fully active coil. Visual observations indicated that a wear scar was formed on the first active coil and the fracture surface showed radiating ridges emanating from the wear scar. Scanning electron microscopy examination showed crescent shaped region and beach marks, typical of fatigue failure. ZnCaph phosphate layer and painting around the contact zone were worn out due to contact and friction and resulted in corrosion and corrosion pits induced local stress concentration. Stress analysis indicated severe stress singularities at the edges of the contact zone, which facilitated cycle slip and fatigue crack nucleation. Recommendations were also made for improving the fatigue performance of the suspension springs.
An interresting paper published in « International Journal of Mechanical Engineeering and Robotics Research« . This paper focuses on the failure of crankshaft due to fatigue which are put into service in several aplications. Crankshaft is important part in al types of engines employed in aplications like aircraft, reciprocating compresor, marine engine, vehicle engine as wel as diesel generator. The failure of crankshaft is due to fatigue resulting into cracks on the surface of crankshaft and efect of residual streses due to filet roling proces. The motivation behind this paper is to study how fatigue phenomenon leads to the failure of the crankshaft.
Failure analysis of a shaft used in a bridge crane has been carried out. The shaft was fractured in the keyway with evidence of fatigue.
This paper published in » Engineering Failure Analysis » was finded on ScienceDirect.com.
Read the article : click here
In July 1968 the Swedish motor vessel “MV Stureholm” traveled from Sweden across the North Atlantic with destination to the American gulf harbours. About 100 nautical miles north of the peninsula Yucatan the 9,000 HP diesel engine failed as a consequence of fatigue failure of the crankshaft. The ship was disabled and had to be towed to Veracruz, Mexico. The Swedish shipowning company decided to perform a temporary repair in Veracruz by welding the fatigue crack. Back in Sweden the damaged but repaired crankshaft was dismounted from the engine and inspected by surveyors. The result was that a fatigue crack had initiated from a subsurface solidification (hot) crack.
This paper brings out the detail of investigation carried out. Read more at : Failure of a Motor Vessel’s Crankshaft 1968.
A new publication of the International Journal of Electrochemical Science, May 1, 2013 …
An extensive investigation into the erosion–corrosion behavior and failure analysis of an offshore steel tubular joint has been carried out by various electrochemical techniques, visual inspection, optical microscope examination, mechanical testing, microstructure examination, chemical analyses, Scanning Electron Microscope (SEM) examination, Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD).
Via ScienceDirect.com, un article à paraître dans Engineering Failure Analysis, concernant une enquête sur ruptures de fatigues de composants d’hélicoptères- Survey of fatigue failures in helicopter components and some lessons learnt.
In gas turbine power plants, a fan is used as a cooling system to dissipate generated heat in coils (copper conductors) and generator electric circuits at the end sides of its rotor. In some cases, fracture of blades causes short circuit between rotor and stator and consequently generator explosion and made lot of financial problems. The fracture of cooling fan blades has been occurred five times at the turbine side of the generator in our case of study, just 100 hr after resuming operation after overhaul.
Un papier intéressant publié par le « 18th International Ship and Offshore Structures Congress » concernant les développements récents de méthodes d’évaluation de propagation de fissures de fatigue appliquées à la construction navale et offshore est consultable en ligne. Il s’agit d’un document de synthèse réalisé par l’ISSC Committee III.2, Fatigue and Fracture.
Suivez le lien : http://139.30.101.246/ISSC2012/images/stories/Proceedings/issc2012-vol1-com-III.2.pdf
Ce congrès s’est tenu du 9 au 13 septembre 2012 à Rostock en Allemagne.
