Systematic Study on Filament Fracture Distribution in ITER ${\hbox {Nb}}_{3}{\hbox {Sn}}$ Strands
Systematic Study on Filament Fracture Distribution in ITER ${\hbox {Nb}}_{3}{\hbox {Sn}}$ Strands
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DOI：
10.1109/tasc.2009.2018082
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发表时间：
2009-06
影响因子：
1.8
通讯作者：
A. Nijhuis;Y. Miyoshi;M. Jewell;W. Abbas;W. Wessel
中科院分区：
文献类型：
--
作者：
A. Nijhuis;Y. Miyoshi;M. Jewell;W. Abbas;W. Wessel
在ITER CICCs中，由于热压缩和电磁载荷，链经历不同的机械应变水平，积累成严重的周期性弯曲和接触应变。根据布线模式的选择，应变可能超过不可逆极限，导致Nb3Sn长丝出现裂纹和导体性能下降。我们提出了一个系统的显微镜研究长丝断裂在逐渐变化的轴向拉伸应变水平在青铜和内部锡加工类型的Nb3Sn ITER链。在4.2 K下测量了金属丝的轴向应力-应变关系，每个样品的峰值载荷从0.0%依次增加到0.7%。从标本的切割截面制备纵向截面。因此，可以研究孤立细丝中的裂纹模式和分布作为外加应变的函数，揭示不同的断裂机制。电测量是用外加应变进行的，特别注意拉伸应变范围。最后，将微观信息与观察到的宏观I - c降解相关联。
In ITER CICCs, the strands experience varying mechanical strain levels due to thermal compression and electromagnetic loading, cumulating into severe periodic bending and contact strain. Depending on the choice of the cabling pattern, the strain may exceed the irreversibility limit leading to cracks in the Nb3Sn filaments and degraded performance of the conductors. We present a systematic microscopy study of filament fracture at gradually varied axial tensile strain levels in a bronze and internal tin processed type of Nb3Sn ITER strand. The axial stress-strain relation of the wires was measured at 4.2 K, up to a different peak load for each sample, successively increasing from 0.0% to 0.7%. Longitudinal cross sections were prepared from cut sections of the specimens. The crack pattern and distribution in the isolated filaments could thus be studied as a function of applied strain, revealing different fracture mechanisms. Electrical measurements were performed with applied strain with special attention for the tensile strain range. Finally, the microscopic information was correlated back to the observed macroscopic I c degradation.