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Characterization of super conducting property from the interdisciplinary viewpoint of superconducting materials technology and solid mechanics

从超导材料技术与固体力学跨学科角度表征超导性能

基本信息

批准号：
10450259
负责人：
OCHIAI Shojiro
金额：
$ 8.13万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

The superconducting properties such as critical temperature, current and upper magnetic field change when mecahnical and electro-magnetic forces are exterd on the superconducting wires during fabrication and/or service. In this work, by combining the knowledges in the fileds of superconducting materials and mechanics, the nucleation, growth and accumulation of damages under staic and cyclic stresses and their influences on superconduing properties of Nb_3Al and Nb-Ti composite wire were clarified. Main results are summaized as follows. (1) The preferred orientation of the filaments and stabilizing copper were clarified by the neutron diffraction method. (2) Nb_3Al filament is broken in a brittle manner, while Nb-Ti one, having ductility, shows mumtiple necking due to the mechanical in teraction with surrounding copper, which acts to keep high critical current density up to high applide strain. (3) In spite of large scatter of strength of Nb_3Al filaments, the scatter of strength of composite wire is small. This feature could be reproduced by a Monte Carlo simulation method in the compuetr. The present results first demonstrate the high reliability of composite wire. (4) Under cyclic stress, crack forms first in the copper (stage I)) and propagate into the core portion(Stage II). In this process, filamenst are broken, resulting in low critical current and low residual strength.

当在制造和/或使用期间对超导线材施加机械力和电磁力时，诸如临界温度、电流和上磁场等超导特性会发生变化。本工作结合超导材料和力学领域的知识，阐明了静态应力和循环应力下损伤的形核、生长和累积及其对Nb_3Al和Nb-Ti复合材料超导性能的影响。主要结果总结如下。 (1)通过中子衍射法阐明了细丝的择优取向和稳定铜。 (2) Nb_3Al细丝以脆性方式断裂，而Nb-Ti细丝具有延展性，由于与周围铜的机械相互作用而表现出多处颈缩，其作用是在高施加应变下保持高临界电流密度。 (3)尽管Nb_3Al丝的强度分散性较大，但复合丝的强度分散性较小。这一特征可以通过计算机中的蒙特卡罗模拟方法来重现。目前的结果首先证明了复合线材的高可靠性。 (4)在循环应力下，裂纹首先在铜中形成（阶段I））并扩展至芯部（阶段II）。在此过程中，细丝被破坏，导致临界电流低和残余强度低。