Archives du mot-clef creep

Premature Failure of Dissimilar Metal Weld Joint at Intermediate Temperature Superheater Tube

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A new case study on Sciencdirect.com. This article was published in « Case Studies in Engineering Failure Analysis » of april 2015.

Premature Failure of EPRI recommended nickel based filler for Dissimilar Metal welds (DMW) such as in the present study has been investigated to determine the root causes. The mechanism involved a creep stage I process on the alloy steel side due to improper PWHT leading to undesirable carbides precipitation increasing the hardness. Therefore, the sensitivity of the welding to micro-cracking combined to bending stresses involvement induced a premature failure within short time of operation.

Read more at : Premature Failure of Dissimilar Metal Weld Joint 

Study on the creep behavior of bonded metallic joints

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a test specimenBonded joints have been used as the main alternative to join components made of different materials or not. Literature shows that although prior studies focused on the characterization of several mechanical properties related to joints, little is known about the creep behavior of bonded joints. This work  studies the behavior of single-lap joints (SLJ) made of metallic substrate and bonded with epoxy and polyurethane adhesives. Results show that, for long term applications, the average tensile strength isn’t enough to guarantee project safety. An initial model for the creep behavior of bonded joints is proposed.

Cliquez pour télécharger le texte complet de l’article paru via :  http://www.appliedadhesionscience.com/content/pdf/2196-4351-2-8.pdf

Leak-before-break for piping systems of fast breeder reactor

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The Leak-Before-Break (LBB) concept has an effect on the safety design of Fast Breeder Reactors (FBRs), and thus its assessment has been one of the most significant issues. In the case of a commercial-scale FBR, since the main loads are the thermal expansion and thermal transient stresses, ferrite steel with a low thermal expansion rate has been a candidate material. A conventional LBB assessment method is insufficient to consider these characteristics, thus an advanced method is required.

  • The LBB assessment to ferrite pipes with thin walls and large diameters is proposed.
  • The surface resistance correction factor was improved for low-pressure.
  • The R6 method was applied to an unstable fracture assessment for postulated cracks.
  • A buckling assessment was introduced for the critical crack length for elbows.

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

Modelling of creep in Inconel 706 turbine disc fir-tree

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Afin d’optimiser le fonctionnement et l’entretien des turbines à gaz, il est nécessaire de mieux comprendre le résiduel de vie en fluage du disque de turbine (à l’interface disque-pied de sapin). L’instrument proposé dans l’article paru dans Materials Science and Engineering de décembre 2012, a une précision de ± 0,01 mm. Il devrait être en mesure de capter la croissance de fluage qui a eu lieu dans l’intervalle entre la dernière révision et le prochain entretien (72.000 h).