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Basic modelling of tertiary creep of copper
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.ORCID iD: 0000-0002-8494-3983
2018 (English)In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 53, no 9, p. 6850-6863Article in journal (Refereed) Published
Abstract [en]

Mechanisms that are associated with acceleration of the creep rate in the tertiary stage such as microstructure degradation, cavitation, necking instability and recovery have been known for a long time. Numerous empirical models for tertiary creep exist in the literature, not least to describe the development of creep damage, which is vital for understanding creep rupture. Unfortunately, these models almost invariably involve parameters that are not accurately known and have to be fitted to experimental data. Basic models that take all the relevant mechanisms into account which makes them predictive have been missing. Only recently, quantitative basic models have been developed for the recovery of the dislocation structure during tertiary creep and for the formation and growth of creep cavities. These models are employed in the present paper to compute the creep strain versus time curves for copper including tertiary creep without the use of any adjustable parameters. A satisfactory representation of observed tertiary creep has been achieved. In addition, the role of necking is analysed with both uniaxial and multiaxial methods.

Place, publisher, year, edition, pages
SPRINGER , 2018. Vol. 53, no 9, p. 6850-6863
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-223768DOI: 10.1007/s10853-017-1968-7ISI: 000424874900048Scopus ID: 2-s2.0-85040081835OAI: oai:DiVA.org:kth-223768DiVA, id: diva2:1188359
Funder
Swedish Nuclear Fuel and Waste Management Company, SKB, 16884
Note

QC 20180307

Available from: 2018-03-07 Created: 2018-03-07 Last updated: 2018-05-16Bibliographically approved
In thesis
1. Fundamental models and testing of creep in copper
Open this publication in new window or tab >>Fundamental models and testing of creep in copper
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Many sustainable technologies for energy production, for example, generation IV nuclear system, demand the use of materials operating at elevated temperatures for long duration of up to 60 years. Requirements that are even more stringent are found for creep exposed copper canisters for disposal of spent nuclear waste. The canisters should stay intact for thousands of years. Traditional design procedures that involve empirical extrapolation of creep data are no longer reliable for such extended times. Instead physically based material models have to be used.

The final stage of creep before rupture, tertiary creep has been handled with empirical methods with adjustable parameters in the past, which makes it difficult to safely identify the controlling mechanisms. A physically based model has been developed for copper taking the substructure, cavitation and necking into account.

To improve the understanding of the important contribution from particles to the creep strength an earlier formulated model has analyzed and further developed. The model has successfully been able to describe the temperature and stress dependence of precipitation hardening for copper-cobalt alloys, where this contribution totally dominates the creep strength.

Multiaxial stress states are crucial for practically all high temperature applications. Fundamental material models have been extended for such conditions. These models have been compared with strain and stress controlled tests for notched specimens that have been performed.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2018. p. 149
Series
TRITA-ITM-AVL ; 2018:25
Keywords
Copper; Creep tests; Multiaxial stress state; Finite element method; Basic modelling; Tertiary creep; Precipitation hardening
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-227968 (URN)978-91-7729-773-4 (ISBN)
Public defence
2018-06-12, Kollegiesalen, Brinellvägen 8, floor 4, stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2018-05-17 Created: 2018-05-15 Last updated: 2018-05-17Bibliographically approved

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