Authors: Al-Abed, B.; Timmins, R.; Webster, G.A.; Loveday, M.S.

Source: Materials at High Temperatures, Volume 16, Number 3, August 1999 , pp. 143-158(16)

Publisher: Science Reviews 2000 Ltd

Abstract:

The results of a European collaborative project aimed at validating a Code of Practice for notched bar creep rupture testing and interpretation of results are presented. Several laboratories from different European Union member states were selected to undertake a comprehensive test programme using circumferentially double notched bars possessing a range of notch acuity ratios. The effects of notch spacing and specimen size were investigated. Inelastic finite element analysis was conducted for establishing the important stress components and stress ratios that are considered instrumental in determining the multiaxial stress rupture criterion (MSRC) for a given material and loading condition. The results of the work have validated the concepts and procedures recommended in the Code of Practice in terms of carrying out the tests and the simplified procedures for the interpretation of results. New finite element analysis has resulted in revised estimates of the multiaxial skeletal point stress components that enter the MSRC. The finite element work is supported by the experimental results in establishing the minimum notch spacing recommended for testing double notched bars. In addition, selected tests revealed the absence of any significant effect of specimen size on notched bar rupture life, thus supporting the use of miniature testpieces even when only a few grains span the minimum section across the notch throat region of the testpiece. The work is supplemented by metallographic examination of failed notched bars which is used to relate damage evolution to the stress distributions predicted by finite element analysis. The results demonstrate the usefulness of the approach recommended in the Code of Practice for establishing the MSRC. This has been borne out by a series of tests undertaken on three engineering materials possessing a wide range of uniaxial creep ductilities, and each displaying a different MSRC. These differences in multiaxial creep rupture behaviour have been attributed to the differences in uniaxial tertiary creep ductility and its variation with stress state.

Keywords: notched bar creep rupture testing

Document Type: Research article

DOI: http://dx.doi.org/10.3184/096034099783641155

Affiliations: 1: Plant Engineering Division, ERA Technology Ltd. UK

Publication date: 1999-08-15

More about this publication?

• Materials at High Temperatures serves the needs of those who develop and use materials for high temperature applications. It publishes peer reviewed contributions relating to high temperature applications in the power, chemical, engine, processing and furnace industries.

  The effects of high temperatures on corrosion, fatigue, creep, strength and wear in alloys, intermetallics, ceramics, refractories and composites are covered. Papers dealing with aspects of materials usage including modelling of behaviour and life prediction will be particularly welcome. The journal has a policy of emphasizing practical aspects and authors presenting results from research programmes are encouraged to relate these, if possible, to actual or potential applications.

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