Technology Reviews

The European Creep Collaborative Committee (ECCC) Approach to Creep Data Assessment

[+] Author and Article Information
Stuart Holdsworth

 EMPA Swiss Federal Laboratories for Materials Testing and Research, CH-8600 Dubendord, Switzerland

J. Pressure Vessel Technol 130(2), 024001 (Mar 25, 2008) (6 pages) doi:10.1115/1.2894296 History: Received May 07, 2007; Revised October 25, 2007; Published March 25, 2008

The European Creep Collaborative Committee (ECCC) approach to creep data assessment has now been established for almost ten years. The methodology covers the analysis of rupture strength and ductility, creep strain, and stress relaxation data, for a range of material conditions. This paper reviews the concepts and procedures involved. The original approach was devised to determine data sheets for use by committees responsible for the preparation of National and International Design and Product Standards, and the methods developed for data quality evaluation and data analysis were therefore intentionally rigorous. The focus was clearly on the determination of long-time property values from the largest possible data sets involving a significant number of observations in the mechanism regime for which predictions were required. More recently, the emphasis has changed. There is now an increasing requirement for full property descriptions from very short times to very long and hence the need for much more flexible model representations than were previously required. There continues to be a requirement for reliable long-time predictions from relatively small data sets comprising relatively short duration tests, in particular, to exploit new alloy developments at the earliest practical opportunity. In such circumstances, it is not feasible to apply the same degree of rigor adopted for large data set assessment. Current developments are reviewed.

Copyright © 2008 by American Society of Mechanical Engineers
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Figure 1

Schematic representation of creep-rupture curve showing primary (P), secondary (S), and tertiary (T) deformation regimes

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Figure 7

Comparison of observed and predicted times to 1% creep strain for a constitutive eauqtion providing a good fit to the experimental 214%CrMo data (i.e., Z∼2)

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Figure 8

Schematic representation of stress-relaxation at constant temperature and constant εt

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Figure 9

Part of large multitemperature, multicast, multisource stress relaxation dataset for a low alloy ferritic bolting steel

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Figure 3

Schematic representation of regimes of rupture ductility

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Figure 4

Large multitemperature, multicast, multisource creep-rupture dataset for 214%CrMo steel

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Figure 5

Steps in the ECCC creep rupture data assessment procedure (the references in parentheses refer to sections in the ECCC Recommendations Vol. 5, Part Ia (2))

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Figure 6

Minimum Au(T) rupture elongation profiles for 11%CrMoVNb steel

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Figure 2

Schematic representation of (a) the T,σo (dependent variable) conditions for three creep-rupture tests at three temperatures, (b) the corresponding ε(t) (response variable) test records, and (c) the resulting tu(T,σo) data points




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