| 1. |
- Andersson, Henrik C. M., et al.
(författare)
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Creep testing of thick-wall copper electron beam and friction stir welds
- 2004
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Ingår i: Materials Research Society Symposium Proceedings. - 0272-9172 .- 1946-4274. - 1558997741 ; 824, s. 51-56
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Tidskriftsartikel (refereegranskat)abstract
- Thick section copper canisters are planned to be used as a corrosion protection of nuclear waste disposal containers for long term underground deposal in Sweden. The copper canisters will have the top and possibly the bottom lid welded to the canister walls using electron beam or friction stir welding. Due to the high external hydrostatic pressure and the relatively high temperature of the waste during the first one hundred years the copper will creep. The creep process will close the manufacturing gap between the cast iron container and the copper canister. The creep ductility must be sufficient to avoid cracking of the weld. Specimens cut from the friction stir welds and the electron beam welds have been creep tested at temperatures ranging from 75 to 175 degreesC. Cross-weld specimens were used for both friction stir and electron beam welds. Weld metal, heat affected zone and base metal were also studied for friction stir welds. The results for the electron beam welds show that the main creep deformation is concentrated to the weld metal where the failure takes place. Weld metal and most cross-weld tests of friction stir weld material show similar creep lives and ductility as base metal tests. Ductility at rupture was found to exceed 30% for friction stir weld specimens, and the Norton power law exponent was determined to be between 30 and 50.
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| 2. |
- Andersson-Östling, Henrik C.M., et al.
(författare)
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Influence of phosphorus, sulphur and grain size on creep in pure copper
- 2009
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Ingår i: Materials Science and Technology. - 0267-0836 .- 1743-2847.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Uniaxial creep tests have been performed at 175 °C to study the influence of phosphorus, sulphur and grain size on the creep properties of oxygen free copper. Copper with no phosphorous content and copper with 2000 μm grain size showed lower creep strength and ductility than the reference material which contained 58 ppm phosphorous and had 350 μm average grain size. Phosphorous content of 29 and 106 ppm showed no difference in relation to the reference material, and neither did grain sizes of 100 and 800 μm average grain size. 6 or 12 ppm sulphur did not affect the creep properties at all. The main creep rupture mechanisms were found to be cavitation and microcracking at the grain boundaries. The observed influence of P on creep is consistent to previously published models both with respect to creep rate and creep ductility.
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| 3. |
- Andersson-Östling, Henrik C.M., et al.
(författare)
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Testing and modelling of creep in copper friction stir welds
- 2009
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Ingår i: Materials Science and Technology. - 0267-0836 .- 1743-2847.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Specimens cut from friction stir welds in copper canisters for nuclear waste have been used for creep experiments at 75°C. The specimens were taken from a cross-weld position as well as heat affected zone and weld metal. The weld specimens exhibited shorter creep lives than the parent metal specimens by a factor of three in time. The cross weld and HAZ specimens were shorter by an order of magnitude when compared to the weld metal. The creep exponent was in the interval 50 to 69 implying that the material was well inside the power-law breakdown regime. The ductility properties expressed as reduction in area were not significantly different in the weld zones and all the rupture specimens demonstrated valu esexceeding 80%. The stationary creep rate for the parent metal was consistent with a previously developed model. The primary creep was successfully modelled. Weld reduction factors have been obtained by comparing the results from base metal tests and weld tests. Measured values at 75 °C for are about 6% for friction stir welds and 14% for electron beam welds.
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| 4. |
- Wu, Rui, et al.
(författare)
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Creep properties of phosphorus alloyed oxygen free copper under multiaxial stress state
- 2010
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Ingår i: BALTICA VIII. - : TECHNICAL RESEARCH CENTRE FINLAND. - 9789513875916 ; , s. 178-195
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Konferensbidrag (refereegranskat)abstract
- Creep tests have been carried out at 75 degrees C using double notch specimens with notch acuities of 0.5, 2, 5, and 18.8, respectively. The creep lifetime for notched specimens is considerably longer than that for the smooth one at a given net section stress, indicating that the investigated Cu-OFP is notch insensitive (notch strengthening). The creep lifetime is notch acuity dependent. The sharper the notch, the longer the creep lifetime is. The creep deformation is to a significant extent concentrated to the region around the notches. Both axial and radial strains on the failed notch are several times larger than those on the unbroken one. Transgranular failure is predominant, independent of stress, rupture time, and notch acuity. To interpret the testing results, finite element computations have been performed using fundamental constitutive equations. The FEM-modelling could represent the creep strain versus time curves for the notched specimens in a satisfactory way. From the FEM-computations a stationary creep stress could be assessed. For a given stationary creep stress, the rupture time can be estimated from the corresponding uniaxial data. This relation can be used to estimate the rupture time for components exposed to creep.
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