Publication Cover
Energy Materials
Materials Science and Engineering for Energy Systems
Volume 12, 2017 - Issue 1: Themed Issue on High Temperature Deformation
304
Views
0
CrossRef citations to date
0
Altmetric
Original Research Paper

Deformation, diffusion and ductility during creep – continuous void nucleation and creep-fatigue damage

Pages 121-133 | Received 22 Apr 2016, Accepted 18 Oct 2016, Published online: 11 Nov 2016
 

Abstract

It is shown that the assumption of unit (negative) slope in the well known Monkman–Grant plot of time to failure against minimum creep rate is too restrictive. By acknowledging observed slopes in the range 0.8–1, a ductility–strain-rate relation is deduced where ductility decreases with reducing strain rate. This in turn has implications for the ductility exhaustion method as applied during stress relaxation in the dwell period of low cycle fatigue tests of austenitic steels at elevated temperature. The simple method is used to calculate the cyclic creep damage in typical tests on austenitic steels in the region 550–650 °C and is compared to other calculations as employed in the R5 high temperature assessment procedure. The assumption of a uniform nucleation rate of grain boundary voids with creep strain goes some way to predicting the slope of the ductility–strain-rate relation. Both the ‘unconstrained’ and ‘constrained’ (lower shelf) regions of void growth are discussed.

Acknowledgements

As ever, the author would like to thank Mr M. W. Spindler for discussions and in this instance for providing extra information on creep and relaxation data.

Reprints and Corporate Permissions

Please note: Selecting permissions does not provide access to the full text of the article, please see our help page How do I view content?

To request a reprint or corporate permissions for this article, please click on the relevant link below:

Academic Permissions

Please note: Selecting permissions does not provide access to the full text of the article, please see our help page How do I view content?

Obtain permissions instantly via Rightslink by clicking on the button below:

If you are unable to obtain permissions via Rightslink, please complete and submit this Permissions form. For more information, please visit our Permissions help page.