Reversibility of micro-yielding and critical current in a YBCO-coated conductor caused by a uniaxial tensile load
Reversibility of micro-yielding and critical current in a YBCO-coated conductor caused by a uniaxial tensile load
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DOI：
10.1088/0953-2048/20/9/s15
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发表时间：
2007-09-01
影响因子：
3.6
通讯作者：
Otto, Alexander
中科院分区：
文献类型：
--
作者：
Osamura, Kozo;Sugano, Michinaka;Otto, Alexander
精确研究了基于 Ni-W 基体的 YBa2Cu3Ox (YBCO) 涂层导体的变形行为及其对临界电流的影响。从室温拉伸试验来看，涂层导体整体的永久应变变化分为微观屈服和宏观屈服两个区域。 Spring8 通过同步加速器辐射进行的精确晶格常数测量表明，YBCO 层中的永久应变具有与上述两个屈服区域相关的两种状态。在微屈服区域，YBCO 层中的永久应变与金属部件中的永久应变相同，这表明 YBCO 层表现出弹性，并且没有引入任何类似损伤的裂纹。在宏观屈服区，与金属部件相比，YBCO 层中的永久应变较小，这表明在加载过程中 YBCO 层中引入了类似损伤的裂纹，并且在零外部载荷下保持不变。在那里，总长度的不变量是由类似损伤的裂纹的存在来调节的。通过加载/卸载实验评估临界电流的可逆性。确保可逆极限的永久应变和相应的外加应变分别为 0.17% 和 0.52%。该可逆极限与微屈服极限一致。此外，作为应变函数的临界电流的不可逆退化被认为与宏观屈服有关。
The deformation behaviour of a YBa2Cu3Ox (YBCO)-coated conductor based on Ni-W substrate and its influence on the critical current were precisely investigated. From a room temperature tensile test, the change of permanent strain as a whole of the coated conductor was divided into two regions of micro- and macroscopic yielding. The precise lattice constant measurement by synchrotron radiation at Spring8 revealed that the permanent strain in the YBCO layer was characterized by two regimes related just to the two regions of yielding mentioned above. In the micro- yielding region, the permanent strain in the YBCO layer was identical with that in the metallic components, suggesting that the YBCO layer behaves elastically and any damage-like cracks were not introduced. In the macroscopic yielding region, the smaller permanent strain in the YBCO layer compared with the metallic components suggested that damage-like cracks were introduced in the YBCO layer during loading and remains under zero external load. There the invariant of total length is accommodated by the existence of damage-like cracks. The reversibility of the critical current was evaluated by loading/unloading experiments. The permanent strain ensuring the reversible limit and the corresponding applied strain were found to be 0.17% and 0.52%, respectively. This reversible limit coincided with the limit of micro-yielding. Furthermore the irreversible degradation of the critical current as a function of strain is suggested to relate to the macroscopic yielding.