1. Error estimates in extrapolation of creep rupture data and its application to an austenitic stainless steel.
- Author
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Sandström, Rolf and He, Jun-Jing
- Subjects
- *
AUSTENITIC stainless steel , *EXTRAPOLATION , *AUSTENITIC steel , *STAINLESS steel , *CREEP (Materials) , *CONSTRAINED optimization - Abstract
Although fundamental models have been developed for time extrapolation of creep rupture data, empirical methods are still dominating. One limitation with the empirical methods is that no systematic way of estimating the error in the results has been available. To remove this limitation, formulae for error estimates are developed in the present paper. Error estimates are first established for single creep rupture curves. Then error estimates are formulated for creep data at several test temperatures assessed with Time-Temperature Parameters (TTPs). A new requirement is introduced in the optimization, namely that the first and second derivatives of the rupture curve should be negative, referred to as constrained. The constrained optimization significantly reduces the error in the extrapolated values. The constrained procedure is applied to the austenitic steel Sanicro 25. The procedure gives quite a stable result, and the post-assessment tests developed by ECCC are satisfied automatically for five common TTPs tested. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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