Analysis of Nb3Sn Strand Microstructure After Full-size SULTAN Test of ITER TF Conductor Sample

Kaverin, D. S.; Potanina, L.V.; Shutov, K. A.; Vysotsky, V.S.; Tronza, V.; Mitin, A.E.; Abdyukhanov, I. M.; Alekseev, M. V.

doi:10.1016/j.phpro.2015.06.154

Cited by 10 publications

(4 citation statements)

References 7 publications

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“…In [7], studies were carried out on strands taken from a conductor, which showed a significant decrease in Tcs during testing. In another work [8], similar studies were carried out on strands taken from another conductor, which, on the contrary, showed an increase in Tcs during these tests. In both cases, significant breaks in the superconducting filaments in the strands were found, especially in the area near the conductor jacket, where the magnetic field is maximum.…”

Section: B Filaments Crackingmentioning

confidence: 84%

Tcs evolution of CICC during Testing

Kaverin¹

2021

Preprint

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139 conductors were manufactured for the magnetic system of the ITER toroidal field coils in total by 6 different teams based on 5 different suppliers of Nb3Sn wires. Despite the fact that all conductors and superconducting wires were manufactured according to the same criteria, there were some differences in the manufacturing technologies of the components themselves, and in the result of the acceptance tests. Samples of some of the conductors passed acceptance tests, where the dependence of Tcs on the number of cycles of inputting the operating current into the samples when they were in a magnetic field was determined. The results of these tests showed that there are not only quantitative, but also qualitative differences in the Tcs (N) dependence. These differences are also observed within the same supplier. It would be useful to understand which parameters most strongly contribute to Tcs (N) in order to possibly improve this characteristic. For this purpose, the article provides a statistical analysis of the test results of 49 samples of conductors. The results are being discussed.

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Section: B Filaments Crackingmentioning

confidence: 84%

Tcs evolution of CICC during Testing

Kaverin¹

2021

Preprint

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“…The mechanical properties of Nb 3 Sn materials are similar to those of ceramics; therefore, brittle fracture occurs when they are subjected to tiny deformations. As such, many experts have started to concentrate on investigating Nb 3 Sn filament fracture [41][42][43][44][45][46][47][48]. Curtin and Zhou [41,42] hypothesized that filament breakage is a random process related to axial stress, and the filament fracture length could be described using the Weibull distribution function.…”

Section: Introductionmentioning

confidence: 99%

“…Consequently, the effect of internal fiber damage on the physical properties and mechanical behavior of the strand must be considered. To analyze the temperature stress caused by heat treatment and the influence of the twisting process on the fracture damage of strands, Shen et al [47,48] used laser-scanning microscopy to study Nb 3 Sn strands in TF CICC cable. Comparing the micrographs of strands before and after heat treatment under artificial bending, it could clearly be observed that the internal fibers of strands after heat treatment and repeated bending were severely damaged.…”

Section: Introductionmentioning

confidence: 99%

Elastic–Plastic Mechanical Behavior Analysis of a Nb3Sn Superconducting Strand with Initial Thermal Damage

Zhang

Shi

2022

Applied Sciences

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It is well known that the parameters of Nb3Sn superconducting strands are strain sensitive, and the internal brittle Nb3Sn filament can easily break under deformations. A temperature difference from the preparation temperature of about 1000 K to the cryogenic working environment of 4.2 K damages brittle Nb3Sn fibers before working. Based on the Curtin–Zhou model, the damage theory for fiber-reinforced composites is utilized to study the influence of filament fractures caused by thermal stress. According to the typical multi-scale geometric of the EAS-Nb3Sn strand (European Advanced Superconductor, EAS), an efficient hierarchical homogenized calculation model considering filament fracture and matrix plasticity was established. In this work, we took the filament fracture caused by both thermal stresses and mechanical loads into consideration using the secant modulus and simultaneously had the impact of the plastic constitutive of the bronze matrix and the copper protective layer. Mechanical parameters, such as the homogenized secant modulus, shear modulus, and Poisson’s ratio in different directions of level scale, were predicted at various temperatures. The elastoplastic mechanical behavior of the strands subjected to axial load was analyzed, and the results were in good agreement with the experiment. The initial thermal fiber fracture has non-negligible effects on the mechanical properties of the EAS-Nb3Sn superconducting strand and play the role in accelerating the increase in fiber breakage.

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“…The, as delivered, Nb 3 Sn strands have a twisted arrangement around their own axis, with a pitch of approximately 15 mm. The Nb 3 Sn strands used in the production of the TF conductors are fabricated using both the ‘bronze-route’ and the ‘internal tin’ processes 6 , 7 . The superconducting Nb 3 Sn composition only forms in the individual strands after the heat treatment of the whole assembled CICC.…”

Section: Introductionmentioning

confidence: 99%

High-energy synchrotron X-ray tomography coupled with digital image correlation highlights likely failure points inside ITER toroidal field conductors

Warr

Jewell

Mitchell

et al. 2021

Sci Rep

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Two sections of heat-treated (HT) and non-heat-treated (NHT) Cable-in-Conduit Conductor (CICC) of a design similar to the ITER tokomak have been imaged using very high energy X-ray tomography at the ESRF beamline ID19. The sample images were collected at four temperatures down to 77 K. These results showed a greater degree of movement, bundle distortion and touching strands in the NHT sample. The HT sample showed non-linear movements with temperature especially close to 77 K; increasing non-circularity of the superconducting fibre bundles towards the periphery of the CICC, and touching bundles throughout the CICC. The images have highlighted where future design might improve potential weakness, in particular at the outer perimeters of the conductor and the individual sub-cable, ‘petal’ wraps.

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Analysis of Nb3Sn Strand Microstructure After Full-size SULTAN Test of ITER TF Conductor Sample

Cited by 10 publications

References 7 publications

Tcs evolution of CICC during Testing

Tcs evolution of CICC during Testing

Elastic–Plastic Mechanical Behavior Analysis of a Nb3Sn Superconducting Strand with Initial Thermal Damage

High-energy synchrotron X-ray tomography coupled with digital image correlation highlights likely failure points inside ITER toroidal field conductors

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