Neutron Diffraction Study on Prebending Effects for Bronze Route $rm Nb_3rm Sn$ Wires Without Reinforcement
19 Jun 2006-IEEE Transactions on Applied Superconductivity (Institute of Electrical and Electronics Engineers)-Vol. 16, Iss: 2, pp 1228-1231
TL;DR: In this article, the axial residual strain changes from -0.10% to 0.02% but the lateral one is unchanged by applying a repeated bending strain at room temperature, i.e., "prebending strain".
Abstract: The critical current, upper critical field and critical temperature of bronze route Nb3Sn commercial wires are enhanced by applying a repeated bending strain at room temperature, i.e., "prebending strain". In order to investigate the prebending effects from a viewpoint of a residual strain, axial and lateral residual strains were evaluated directly by neutron diffraction at room temperature. We found that the axial residual strain changes from -0.10% to 0.02 % but the lateral one is unchanged by applying a prebending strain of 0.5% for an ordinary bronze route (Nb,Ti)3Sn wires without reinforcement. Hence, in the case of the ordinary Nb3Sn wires without reinforcement, the prebending treatment modifies only the axial residual strain states independently to the lateral one, although it may depend on the wire structure. The critical current properties under the axial tensile strain suggest that the axial residual strain is reduced by about 0.11% but the radial residual strain unchanged by the prebending treatment of 0.5%. This is consistent with the results of the neutron diffraction
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TL;DR: In this article, the effects of 3D strain on the superconducting properties of composite Nb3Sn wires and cable conductors are reviewed and compared with some experimental data.
Abstract: In order to understand the effects of strain on the superconducting properties in composite Nb3Sn wires and cables, the three-dimensional (3D) strain is very important. Quantum beams such as neutron and synchrotron radiation enable us to quantify the detailed internal strain in any direction nondestructively. Therefore, quantum beams are recognized as a powerful tool to evaluate the 3D strain inside composite materials. The internal strain states of Nb3Sn strands in thick conduits such as cable-in-conduit conductors can also be detected because of the large penetration depth of neutrons. Because of advances in neutron and synchrotron radiation facilities, recent studies have examined the internal strains in composite superconducting wire and cable conductors. This paper reviews recent studies on 3D strains and their effects on the superconducting properties of Nb3Sn wires and cable conductors, along with some experimental data. Other applications of quantum beams for superconducting wires are also introduced briefly.
44 citations
TL;DR: In this article, the authors measured axial and lateral residual strains for the prebent and as-reacted CuNb∕Nb3Sn wires at room temperature and at 7K, in order to investigate the change of the residual strain with prebending treatment.
Abstract: We measured directly by neutron diffraction the axial and lateral residual strains for the prebent and the as-reacted CuNb∕Nb3Sn wires at room temperature and at 7K, in order to investigate the change of the residual strain with prebending treatment. In the axial direction of the wire, the residual strain was changed with 0.20% to the tensile side when measured at both temperatures, while in the lateral direction, the change was 0.08% and 0.03% to the compressive side for the measurements at RT and 7K, respectively. From the obtained data, we estimated the deviatoric strain. At 7K, the value is 0.40% for the as-reacted wires and it reduces to 0.19% when the prebending is applied with a strain epb=0.8%. These results suggest that the reduction of the residual strain in the axial direction as well as in the lateral direction, i.e., of the deviatoric strain is responsible for the observed enhancement in the superconducting properties of the prebent Nb3Sn wires. In addition, we succeeded in the quantitative e...
35 citations
TL;DR: In this article, elastic strain measurements in the different phases of entire non-heat treated and fully reacted Nb3Sn composite strands as a function of uniaxial stress during in situ deformation under neutron beam were reported.
Abstract: The strain induced degradation of Nb3Sn superconductors can hamper the performance of high field magnets. The authors report elastic strain measurements in the different phases of entire non-heat treated and fully reacted Nb3Sn composite strands as a function of uniaxial stress during in situ deformation under neutron beam. After the reaction heat treatment the Cu matrix loses entirely its load carrying capability and the applied stress is transferred to the remaining Nb–Ta alloy and to the brittle (Nb–Ta)3Sn phase, which exhibits a preferential ⟨110⟩ grain orientation parallel to the strand axis.
27 citations
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TL;DR: A cryogenic load frame for stress-strain measurements of materials using a neutron diffractometer at Japan Proton Accelerator Research Complex (J-PARC) Takumi beam line is developed and test results are described by using type-304 stainless steel wire.
Abstract: To prepare for projects such as the Large Hadron Collider upgrade, International Thermonuclear Experimental Reactor and Demonstration reactor, it is important to form a clear understanding of stress-strain properties of the materials that make up superconducting magnets. Thus, we have been studying the mechanical properties of superconducting wires using neutron diffraction measurements. To simulate operational conditions such as temperature, stress, and strain, we developed a cryogenic load frame for stress-strain measurements of materials using a neutron diffractometer at Japan Proton Accelerator Research Complex (J-PARC) Takumi beam line. The maximum load that can be applied to a sample using an external driving machine is 50 kN. Using a Gifford–MacMahon cryocooler, samples can be measured down to temperatures below 10 K when loaded. In the present paper, we describe the details of the cryogenic load frame with its test results by using type-304 stainless steel wire.
13 citations
TL;DR: In this paper, a prebent react-and-wind (R&W) process was developed to demonstrate the applicability of the prebending strain effect to the R&W coil winding process.
Abstract: To demonstrate the applicability of the prebending strain effect to the R&W coil winding process, we have developed the prebent react-and-wind (R&W) process, which is the combination of the conventional R&W process and the prebending treatment. The superconducting and mechanical characteristics were investigated for CuNb/Nb3Sn superconducting wires which were picked up from the prebent R&W coil winding process. The results were compared with that of CuNb/Nb3Sn wires which were prebent manually using a prebending former. The prebending treatment using pulleys enhanced Ic more than the manual prebending treatment. This is explained qualitatively by a difference of the prebending strain distribution. The prebending strain distribution is plain symmetric and axis symmetric in cases of the manual prebending and the pulleyed prebending, respectively. The axis symmetrically distributed prebending strain reduces the residual strain more than the plain symmetrical one. The mechanical property was also enhanced. The slope of the stress-strain curve for the pulleyed prebent samples were steeper than that of as-heat-treated sample. The maximum Ic of the Ic -strain curve was enhanced and the strain value corresponding to the maximum Ic shifted to smaller strain by the pulleyed prebending treatment. Though in the large stress region over 200 MPa, the Ic-stress curves of pulleyed prebent samples and as-heat-treated sample were in good agreement, suggesting that the Ic enhancement effect by the prebending treatment was not beneficial, in the small stress region, it is quite beneficial
13 citations
Cites background from "Neutron Diffraction Study on Preben..."
...Furthermore, neutron diffraction measurement provides that the prebending treatment affects not only the axial strain but also the radial strain distribution [2]....
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References
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01 Jan 1980
TL;DR: In this paper, the effects of formation temperature on the superconducting properties of V3Ga Wires were investigated in the context of multifilamentary composite superconductors.
Abstract: Conventional Composites and National Reviews.- Development of A15 Filamentary Composite Superconductors in Japan.- Development of A15 Multifilamentary Superconductors.- Work in the U.K. on Filamentary A15 Conductor Development.- Development of A15 Multifilamentary Superconductors at Airco.- Review of Superconductor Activities at IGC on A15 Conductors.- Filamentary Nb3Sn Superconductor Manufactured by the Solid-Liquid Diffusion Method.- Multifilamentary Nb3Sn by an Improved External Diffusion Method.- Effects of Formation Temperature on the Superconducting Properties of V3Ga Wires.- Development of Multifilamentary Compound Superconductors.- Flux Pinning in Bronze-Processed Nb3Sn Wires.- An Auger Electron Spectroscopy Study of Bronze Route Niobium-Tin Diffusion Layers.- Mechanical Properties.- The Importance of Being Prestressed.- Studies of the Strain-Dependent Properties of A15 Filamentary Conductors at Brookhaven National Laboratory.- Strain Scaling Law and the Prediction of Uniaxial and Bending Strain Effects in Multifilamentary Superconductors.- Evidence for Microstructural Effects under Strain in Bronze Process Nb3Sn.- Mechanical Properties of High-Current Multifilamentary Nb3Sn Conductors.- Stress Effects on W/Cu Reinforced Nb3Sn Composite Conductors.- Multiply Connected Superconductors.- In Situ and Powder Metallurgy Multifilamentary Superconductors: Fabrication and Properties.- Preparation and Properties of In Situ Prepared Filamentary Nb3Sn-Cu Superconducting Wire.- Superconducting Properties and Coupling Mechanisms in In Situ Filamentary Composites.- Powder Metallurgically Prepared A15 Microcomposite Superconductors.- Critical Currents of Cu-(Nb1?xTax)3Sn In Situ Multifilamentary Wires.- Magnetic Properties of Multifilamentary Nb3Sn Composites.- Alternating Current Losses in Twisted In-Situ Composite Wires.- A15 Multifilamentary Superconductors by the Infiltration Process.- Group Comments.- Report of Magentic Fusion Energy Group.- Report of High Energy Physics Group.- Report of Solid State Physics Group.- Report of Metallurgy Group.- Indexes.- Contributor Index.
109 citations
01 Jan 1980
TL;DR: In this article, it was shown that at 4.2 K, the critical pinning-force density of a wide range of practical conductors obeys a scaling law of the form: ==================\/\/\/\/\/\/£££/$££€££$££ £££
Abstract: Recently it was shown1 that at 4.2 K the critical pinning-force density F in a wide range of practical conductors obeys a scaling law of the form:
$$F = {[B_{c2}^*(\varepsilon )]^n}\,f(b)$$
(1)
where \(B_{c2}^*\) is the bulk upper-critical field at 4.2 K and f(b) is a function only of the reduced magnetic field \(b \equiv B/B_{c2}^*.\) For Nb3Sn conductors, n = 1 ± 0.3. This relation was found to hold for both compressive and tensile intrinsic strain, and is expected to be limited in validity only by the irreversible strain point2 where filament breakage becomes significant (typically at intrinsic tensile strains greater than 0.4 – 0.7% for most highly-reacted Nb3Sn conductors2).
80 citations
TL;DR: In this paper, the authors examined the influences of bending strain at room temperature on the mechanical and superconducting properties in (Nb,Ti)3Sn composite wire and found that the improvement of the critical current and the mechanical properties is due to the local work hardening effects by applying the bending strain.
Abstract: The improvement of stress/strain properties has been observed for the CuNb/(Nb,Ti)3Sn coil made by a react and wind (R&W) method. In the winding and insulation processes, a certain bending strain is applied to the wire and then released at room temperature, which is defined as 'pre-bending' treatment. In order to understand this behaviour, we examine the influences of bending strain at room temperature on the mechanical and superconducting properties in (Nb,Ti)3Sn composite wire. Experimental results for the pre-bent CuNb/(Nb,Ti)3Sn wires show the improvement of the stress dependence of Ic/Icm and the increase of the critical current Ic at zero stress. The calculation on the basis of the distribution of the uniaxial local stress/strain describes the experimental results, qualitatively. We have found that the improvement of the critical current and the mechanical properties is due to the local work hardening effects by applying the bending strain at room temperature.
42 citations
TL;DR: In this paper, the influence of cyclic loading at room temperature on the critical current at 4.2 K of bronze-processed multifilamentary Nb 3 Sn superconducting composite wire was studied.
42 citations