Archives du mot-clef case study

Damage mechanism and prevention of heavy-haul railway rail

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A new interesting paper in  » Engineering Failure Analysis »  of december 2013 published on ScienceDirect.com.

The objective of this paper was to investigate wear and damage behavior of heavy-haul railway rail.

More at : Investigation on the damage mech………

Failure analysis of copper tube

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A new interesting paper in « Engineering Failure Analysis » published on ScienceDirect.com. This paper reports the failure analysis of a leaked copper tube used in a refrigerating plant for carrying polyol ester oil for lubrication and cooling of compressor bearings. Failure had occurred at the bent region of the tube in the form of a wide diametric crack.

More information : Failure analysis of copper tube used in a refrigerating plant.

Stress corrosion cracking in 316L stainless steel

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

There were three consecutive occurrences of bellows failure in a particular pressure safety valve (PSV) of a petroleum refinery within a time span of one week. The bellows were made of 316L grade austenitic stainless steel, and the PSV was mounted on one of the vessels of vacuum gas oil service in a hydrocracker unit. Metallurgical analysis of the failed bellows revealed that the failure had occurred by stress corrosion cracking (SCC). This paper brings out the detail of investigation carried out.

Validation of F-16 Wing Attachment Fitting bolts

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

During a modification programme, the Wing Attachment Fitting (WAF) cadmium-plated steel bolt assemblies from 33 F-16 aircraft were cleaned in a non-approved chemical solution, a paint stripper. This removed much of the cadmium plating, leading to in-service superficial rusting of some bolt ends and nuts. The OEM and chemical manufacturer became concerned about possible hydrogen embrittlement of the bolts owing to exposure to the paint stripper. This paper brings out the detail of investigation carried out.

Fracture analysis of wind turbine main shaft

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Read on Engineering Failure Analysis. Shaft fracture at an early stage of operation is a common problem for a certain type of wind turbine. To determine the cause of shaft failure a series of experimental tests were conducted to evaluate the chemical composition and mechanical properties. The results show that stress concentration on the shaft surface close to the critical section of the shaft due to rubbing of the annular ring and coupled with high stress concentration caused by the change of inner diameter of the main shaft are the main reasons that result in fracture of the main shaft. The contribution of this paper is to provide a reference in fracture analysis of similar main shaft of wind turbines.

Service fatigue cracking in an aircraft bulkhead exposed to a corrosive environment

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This paper presents a supporting case study that examines fatigue cracks that were detected in an F/A-18 Hornet bulkhead during post-service testing and teardown. The in-service phase of the cracking had significant evidence of oxidation on their surfaces which indicated an exposure to a mildly corrosive environment. Both the service and laboratory phases of the cracking were the subject of quantitative fractography and estimates of the crack growth rates were made. A comparison of the in-service and the in-test phases of crack growth indicated that no notable effect on the service part of the fatigue crack could be attributed to its exposure to the service environment.

Read the article on http://www.sciencedirect.com

Stress corrosion and hydrogen induced cracking of a control valve body

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The control valve body failed due to combination of SSC and HIC cracking in wet H2S environment. According to HIC and SSC laboratory tests the best alternative for the valve body alloy is A217-WC9 steel.Anodic polarization curves clearly shows a considerable improvement in pitting resistance.

More information on http://www.sciencedirect.com

Corrosion properties of AISI 321 stainless steel

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The main aim of this study was to analyze the pitting corrosion and stress corrosion cracking which is initiated on prototype cold-formed outer exhaust sleeves during the testing of different cleaning procedures before chromium plating. Various microscopic methods were used to identify the initiation of corrosion and its propagation.

  • Severe corrosion occurred in the cleaning solution containing H2SO4 at elevated temperature.
  • Pitting corrosion has formed on the titanium nitride inclusions.
  • Stress corrosion cracking was caused by deformation martensite.

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Erosion of heat exchangers due to sootblowing

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The erosion rate of convection surfaces is crucial for boiler reliability. This paper presents the impact of the action of a sootblowing stream (steam and air) jet on the sustainability of tubes. The model investigations described here compared the erosion rates of a tube bank while turning on or off an additional jet stream of compressed air that simulates the operation of a sootblower. This paper presents calculations for the erosion loss of a heat exchanger built in the actual object.

Failure analysis of solenoid valve components

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Valve had failed as a result of particles of material becoming trapped between the valve seat recess and the valve seat ball, leading to erosion of the valve seat recess, valve seat ball and the valve operating pin; this allowed hydraulic fluid to flow when the valve was nominally in the de-energised position.The material of construction of the valve seats was not compliant with engineering drawings.The investigation demonstrated the importance of maintaining the cleanliness of hydraulic systems and of the need to control the materials of manufacture in safety critical applications.

Read more at : Failure analysis of solenoid valve components from a hydraulic roof support.