Archives du mot-clef cas concrets

Reduction in diversion due to coil break in CRNO grades of coils

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A new « Case study in Engineering Failure Analysis » published on ScienceDirect.com.

This paper reports investigations after diversion due to coil break in cold rolled non oriented (CRNO) grades of coils showed an increasing trend during Jan–May’12 at Silicon Steel Mill (SSM), Rourkela Steel Plant (RSP). Coil break increased from a level of less than 1% during to a level of 30% in May’12. Samples from hot rolled coils and finished coils were taken and detailed metallurgical investigation was carried out to ascertain the genesis of such defects. Further studies were carried out in the processing lines and material flow was tracked from steel making to final product. The probable reasons were identified and corrective measures were taken leading to reduction in diversion due to coil break less than 2%.

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Brittle fracture of a grade E cast steel knuckle

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A new paper in « Case study in Engineering Failure Analysis » published on ScienceDirect.com. This paper 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.

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A failure study of the railway rail serviced for heavy cargo trains

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rail fractureA paper published in« Case study in Engineering Failure Analysis ». In this case study, a failed railway rail which was used for heavy cargo trains was investigated in order to find out its root cause. The crack is supposed to be initiated from the weaker ferrite networks. Given all of that, the failed railway rail is considered to be caused by overload. It is of great importance to improve the welding technology, and control the load of train in order to prevent similar failure in future.

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Interfering part of a steam turbine journal bearing

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bearing part frettingJournal 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 research, 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 a pelton impeller

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A new topic on « http://www.sciencedirect.com/« .This paper, published in « Engineering Failure Analysis« , presents the analysis of a 16-bucket Pelton impeller from a hydroelectric plant in Colombia, a plant with two turbo generators with a nominal capacity of 2.33 MW each. Multiple cracks were detected one year subsequent to geometry reconstruction welding repair.

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Case Studies in Marine Concentrated Corrosion

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A new paper in « Case study in Engineering Failure Analysis » published on ScienceDirect.com. This paper outlines the problem and analysis techniques in three exemplar case studies of marine concentrated corrosion. The paper includes an outline of some of the relevant literature relating to the use of these modern techniques in identifying marine corrosion products.

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Analysis of cracks generated in the spinning-mandrel teeth

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A new paper in « Case study in Engineering Failure Analysis » published on  ScienceDirect.com. The spinning process, using a splined mandrel, is always prone to premature failure of the splined mandrels. Such a failure is thought to be related to the magnitude of the forming forces exerted on the mandrel by the forming rollers during the spinning process. In the present paper, the characteristic of corner cracks in the mandrel teeth (made of S7 tool steel) of a spinning process has been investigated. Fractography analyses using scanning electron microscopy (SEM) clearly confirm “fatigue” as being the main reason for the failure.

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Failure analysis of an MVR mechanical vapor recompressor Impeller

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This article, published in  » Engeeniring Failure Analysis » of september 2010, describes the root cause failure analysis of a mechanical vapor recompressor (MVR) impeller used in a dairy processing plant. A detailed investigation was commissioned to determine the source of the oscillatory stresses that must have been present to cause fatigue. A vibration analysis indicated large torsional oscillatory stresses, leading to fatigue, were induced by excitation of the 1st and 2nd torsional vibration modes of the MVR impeller and motor system. The excitation was induced by the control system for the motor variable speed drive (VSD).

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Failure Analysis of a Bearing in a Helicopter Turbine Engine

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This article documents the metallurgical evaluation of a rolling element bearing that failed due to electrical discharge damage. This rolling element bearing was used in a helicopter turbine engine that failed in-flight, resulting in a hard landing of the helicopter. Optical and electron microscopy as well as energy dispersive spectroscopy were used to evaluate the bearing. Pitting and material transfer on the external bearing races bearing and mating surfaces revealed that the electrical discharge damage occurred while the engine’s components were not rotating.

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