Multiscale Approach to the Mechanical Behavior of Epoxy Impregnated Nb3Sn Coils for the 11 T Dipole

Daly, Michael; Loffler, Christian; Smekens, D.; Fontenla, Ana Teresa Perez; Frutos, Óscar Sacristán de; Guinchard, Michael; Savary, F.

doi:10.1109/tasc.2018.2807373

Cited by 22 publications

(16 citation statements)

References 12 publications

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“…The stress of most Nb 3 Sn filaments is at the same level, however, the stress of a few filaments at the edge of the strand is significantly larger than the other parts, possibly because it is the contact region between adjacent strands. This phenomenon was also observed in [3]. Considering the stress and strain sensitive nature of the highfield superconductors like Nb 3 Sn, it indicates that the currentcarrying capacity of these filaments will degrade first when the stress level of the strand is high.…”

Section: Resultsmentioning

confidence: 62%

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Study on Internal Strain Distribution of the High-Field Nb₃Sn Superconducting Accelerator Magnets With Homogenization Theory

Zhang

2022

IEEE Access

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To fabricate 10-16 Tesla high-field accelerator magnets, the high-Jc Nb 3 Sn superconductor is one of the most practical choices. However, it is a brittle material and is strain-sensitive. To reduce the potential Jc degradation of the conductor, it is crucial to accurately evaluate the stress of the coils owing to the large Lorentz force during magnet excitation. In the traditional stress analysis of magnets, the coils are usually regarded as homogenized structures using isotropic material coefficients; however, most superconducting (SC) coils have hierarchical and complicated structures. To obtain a more accurate estimation, it is necessary to consider the detailed internal structure of the coils during stress analysis. In this study, the homogenization method was applied to multi-scale stress analysis of a high-field accelerator SC magnet. The effective material coefficients of Nb 3 Sn coils were calculated using this method. Stress analysis of the magnet was performed using the effective material coefficients and isotropic material coefficients for comparison. Compared with the result obtained using isotropic material coefficients, the Von-Mises stress of the coil using effective material coefficients is larger at different load steps. The stress level of most Nb 3 Sn filaments in the strand was higher than that of the coil. The maximum stress of the Nb 3 Sn filaments appeared in the strand contact regions. In addition, there was a significant difference in the average stress of all materials in the strand. These findings will help develop more accurate analysis and simulation models for high-field SC magnets.INDEX TERMS Homogenization method, Nb 3 Sn, stress analysis, superconducting magnet.

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Section: Resultsmentioning

confidence: 62%

“…Multi-scale analysis methods [1], [3]- [9] are appropriate solutions for the above problem. Multiple researchers [7], [9] have developed multi-scale models to study the mechanical behavior of Nb 3 Sn material between the strand and filament levels.…”

Section: Introductionmentioning

confidence: 99%

Study on Internal Strain Distribution of the High-Field Nb₃Sn Superconducting Accelerator Magnets With Homogenization Theory

Zhang

2022

IEEE Access

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“…More refined approaches were used in some cases, as for example modeling the single cables [15], or separating the cable from the insulation [16]. Recently, a coil model at the strand level, with geometry extracted from a coil cross section picture, has been proposed in [17]. A cable and coil modeling strategy at the strand level was proposed in [18], and used to predict the mechanical stiffness of the coil and its dependence on the mechanical properties of the various components.…”

Section: Introductionmentioning

confidence: 99%

A methodology to compute the critical current limit in Nb₃Sn magnets

Vallone¹,

Anderssen²,

Bordini³

et al. 2020

Supercond. Sci. Technol.

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Numerous experiments have shown that the loads applied to Nb3Sn strands and cables can reduce their critical current. Experiments, performed on uniaxially loaded strands, allowed to define clear laws to describe the evolution of the critical surface as a function of the applied current, field, temperature and strain. It is, however, still unclear how these laws can be applied to superconducting magnets. The present paper proposes a methodology to estimate the critical current and temperature margin reduction on superconducting magnets due to stress on the superconducting material. The methodology is tested on the MQXF magnets, a quadrupole developed for the High Luminosity LHC project, and successfully validated by comparing computed strain with data from strain gauge measurements. Results suggested that, because of the stresses arising in winding during assembly, cool-down and powering, the current limit of the magnet is lower than the expected short sample limit, and that the most critical region does not coincide with the peak field location.

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“…The figure shows the modelled deviatoric strain in homogeneous Nb 3 Sn cylindrical 'strands', not taking into account the internal strand composition. More detailed FE modelling shows that further stress-and strain-concentrations occurs within the filamentary zone of the strands [109,186,223]. As mentioned in the Section 3.1, such detailed level of modelling falls outside the scope of this thesis, but also here we can get a feeling for the magnitude of this effect from a strongly simplified model.…”

Section: Influence Of the Confinement Geometry On The Deviatoric Stramentioning

confidence: 92%

“…In accelerator magnets, such strain will typically be due to a combination of stresses imposed during cable-and magnet assembly, of differential thermal contraction during cool-down and of Lorentz force when the magnet is excited. Modelling the resulting strain state of the micron-sized filaments taking into account all the components of a meter-sized magnet as well as their thermo-mechanical history is a daunting task [182][183][184][185][186], which falls beyond the scope of this thesis.…”

Section: Introductionmentioning

confidence: 99%

Transverse pressure effect on superconducting Nb3Sn Rutherford and ReBCO Roebel cables for accelerator magnets

Gao

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Multiscale Approach to the Mechanical Behavior of Epoxy Impregnated Nb3Sn Coils for the 11 T Dipole

Cited by 22 publications

References 12 publications

Study on Internal Strain Distribution of the High-Field Nb₃Sn Superconducting Accelerator Magnets With Homogenization Theory

Study on Internal Strain Distribution of the High-Field Nb₃Sn Superconducting Accelerator Magnets With Homogenization Theory

A methodology to compute the critical current limit in Nb₃Sn magnets

Transverse pressure effect on superconducting Nb3Sn Rutherford and ReBCO Roebel cables for accelerator magnets

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Multiscale Approach to the Mechanical Behavior of Epoxy Impregnated Nb3Sn Coils for the 11 T Dipole

Cited by 22 publications

References 12 publications

Study on Internal Strain Distribution of the High-Field Nb₃Sn Superconducting Accelerator Magnets With Homogenization Theory

Study on Internal Strain Distribution of the High-Field Nb₃Sn Superconducting Accelerator Magnets With Homogenization Theory

A methodology to compute the critical current limit in Nb3Sn magnets

Transverse pressure effect on superconducting Nb3Sn Rutherford and ReBCO Roebel cables for accelerator magnets

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Product

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A methodology to compute the critical current limit in Nb₃Sn magnets