Influence of cyclic loading at room temperature on the critical current at 4.2 K of Nb3Sn superconducting composite wire
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.
About: This article is published in Cryogenics.The article was published on 1992-01-01. It has received 42 citations till now. The article focuses on the topics: Critical field & Stress (mechanics).
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TL;DR: In this article, the peak strain of critical current (Ic) in Y Ba2Cu3O7?? (YBCO) coated conductors was evaluated at temperatures in the range 20?83?K under magnetic fields parallel to the c-axis up to 10?T.
Abstract: The strain effect on critical current (Ic(?)) in Y Ba2Cu3O7 ? ? (YBCO) coated conductors was evaluated at temperatures in the range 20?83?K under magnetic fields parallel to the c-axis up to 10?T. The peaked reversible variation of Ic with applied uniaxial strain was confirmed in the self-field at all tested temperatures. The strain sensitivity increases with increasing temperature, resulting in a more pronounced reversible suppression with strain at higher temperature. Interestingly, it was found that the peak strain corresponding to the maximum of Ic shifts to the compressive side with decreasing temperature. Such a peak shift cannot be explained by a change in the thermal residual strain of the YBCO film, suggesting that the peak strain of the Ic(?) in YBCO coated conductors is not determined only by relaxation of the residual strain. The strain sensitivity of Ic(?) at 60?K becomes greater with increasing magnetic field, while the influence of the magnetic field is much less pronounced at 20?K. The in-field Ic(?), including the compressive strain region as well as the tensile region, shows a double peak behavior at low magnetic field at 77 and 83?K. The temperature and magnetic field effect on Ic(?) in YBCO coated conductors is discussed considering flux pinning within the grains and on grain boundaries.
80 citations
TL;DR: In this article, a variable-temperature probe has been developed to study the effect of strain on the transport properties of superconducting wires and tapes in high magnetic fields, by soldering it to a thick coiled spring and twisting one end of the spring with respect to the other.
Abstract: A variable-temperature probe has been developed to study the effect of strain on the transport properties of superconducting wires and tapes in high magnetic fields. The strain is applied to the wire by soldering it to a thick coiled spring and twisting one end of the spring with respect to the other. Strain can be applied reversibly from −0.7% to +0.7%. Measurements can be performed either in (pumped) cryogen or under vacuum. When immersed in liquid helium at 4.2 K, the probe can carry at least 200 A. From 6 to 16 K, with thin (low-loss) current leads the temperature of the sample is stable to ±45 mK for currents around 15 A, and to ±100 mK for currents around 25 A. With thick current leads, ±10 mK stability is achieved for currents up to 85 A. Full details of the probe design are described. Results obtained for a bronze processed niobium–tin multifilamentary wire are presented.
72 citations
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 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: The bidirectional relationship between the general and particular synthesis concepts of superconducting materials is explored and some key elements to define the concept of 'beautiful' technology in materials science are provided.
35 citations
References
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TL;DR: In this paper, it was shown that the peak in Fp scales as [Hc2(T)]2.5 if the temperature is changed; the maximum value of Fp occurred at the same value of reduced field regardless of temperature.
Abstract: For all hard high‐field superconductors examined to date, there is a maximum in the pinning force density Fp as a function of the reduced magnetic field h. Fietz and Webb first demonstrated in dilute Nb alloys that the peak in Fp scales as [Hc2(T)]2.5 if the temperature is changed; the maximum value of Fp occurred at the same value of reduced field regardless of temperature. Recent data on the temperature dependence of pinning in Nb3Sn, Nb–25% Zr and a Nb–Ti alloy, which exhibits the ``peak effect'', are analyzed to show that similar scaling laws are obeyed by these materials. All presently available evidence indicates however that the reduced field hp at which the maximum Fp occurs, as well as the height and shape of this maximum, can be altered by metallurgical treatment. Apparently weak pinning defects, or widely spaced ones, produce a small peak in Fp(h) at high h whereas strong closely spaced pins produce a large peak in Fp(h) at low h without producing much change in Fp(h) at high h. A model which p...
1,104 citations
TL;DR: In this article, the authors present the basic uniaxial-strain scaling relationship and focus on its application to Nb3Sn conductors, and propose a general scaling relation which unifies the usual temperature scaling relation with this strain-scaling relation.
398 citations
TL;DR: In this article, the performance of high-J c multifilamentary Nb 3 Sn superconductors with widely varying amounts of prestrain and critical field values can be characterized fairly accurately by a single normalized critical field-strain relationship.
Abstract: High-J c multifilamentary Nb 3 Sn superconductors with widely varying amounts of prestrain and critical field values can be characterized fairly accurately by a single normalized critical field-strain relationship. Such a relationship permits first order prediction of critical-current degradation at arbitrary magnetic field magnitudes knowing only two parameters for any conductor, the prestrain and the maximum critical field. Some of the conductor-fabrication factors affecting the parameters are considered.
91 citations
TL;DR: In this article, a critical current study of flexible Nb3Sn multifilamentary composite wires has been conducted at 4 K in magnetic fields to 90 kOe (7.2×106 A/m) while the wire is subjected to high mechanical stresses.
Abstract: A critical‐current study of flexible Nb3Sn multifilamentary composite wires has been conducted at 4 K in magnetic fields to 90 kOe (7.2×106 A/m) while the wire is subjected to high mechanical stresses. The results show that at stresses above 1–2×108 Pa (strains of 0.1–0.2%) the critical current is significantly degraded, with the magnitude of the reduction dependent on reinforcement techniques used in the wire’s construction. The effect increases with magnetic field and results in the introduction of significant resistance at current levels well below the zero‐stress critical current. Design considerations for the use of Nb3Sn wires in the high‐stress environments of large‐scale superconducting magnets are discussed.
66 citations
TL;DR: In this paper, the critical current of a commercial multifilamentary Nb3Sn conductor was measured under the application of uniaxial tension at 4.2 K and following bending at room temperature.
Abstract: The critical current of a commercial multifilamentary Nb3Sn conductor has been measured under the application of uniaxial tension at 4.2 K and following bending at room temperature. Significant reductions in Jc are observed under uniaxial loading. Results are presented for a monolithic conductor manufactured by the bronze diffusion technique and for cable conductors formed by the tin‐dip technique.
45 citations