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- Sui, Fangfei, 1986-, et al.
(författare)
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Fundamental Modelling of Mechanisms Contributing to Tertiary Creep in Copper AT 215 and 250°C
- 2018
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Ingår i: Proceedings of the ASME 2018 Pressure Vessels and Piping Conference. - : ASME International. - 9780791851678
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Konferensbidrag (refereegranskat)abstract
- Extensive creep tests have been performed on oxygen free copper with 50 ppm phosphorus at both low and high temperatures. It is the candidate material for storage of spent nuclear fuel in Sweden. Basic models without fitting parameters have been formulated to reproduce primary and secondary creep. For a long time, only empirical models existed for fitting of tertiary creep. To understand the role of creep damage, including recovery, cavitation and necking, basic models that do not involve adjustable parameters are in urgent demand. Only recently, basic models taking the relevant mechanisms into account have been developed. These models were used to predict the tertiary creep for copper at 75°C. The modelled results were compared with experimental creep curves and good agreement has been found. In the present paper, the models are applied to creep tests at higher temperatures (215 and 250°C). A similar representation with good accuracy is obtained. This demonstrates that the fundamental model for back stress is applicable for the higher temperature tests as well.
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- Sui, Fangfei, 1986-
(författare)
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Fundamental models and testing of creep in copper
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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