Study of Filament Cracking Under Uniaxial Repeated Loading for ITER TF Strands
Study of Filament Cracking Under Uniaxial Repeated Loading for ITER TF Strands
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DOI：
10.1109/tasc.2011.2174554
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发表时间：
2012-06
影响因子：
1.8
通讯作者：
M. Sheth;Peter J. Lee;D. McRae;Charlie Sanabria;W. Starch;Robert Walsh;M. Jewell;Arnaud Devred;D. Larbalestier
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文献类型：
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作者：
M. Sheth;Peter J. Lee;D. McRae;Charlie Sanabria;W. Starch;Robert Walsh;M. Jewell;Arnaud Devred;D. Larbalestier
在诸如ITER的托卡马克中，超导股线由于洛伦兹力加载/卸载和热冷却而遭受弯曲和单轴应变，这可能由于特定的导管中电缆导体（CICC）设计选择而随着时间的推移使性能降级。在重复的单轴向加载的Cu（Sn）矩阵，它周围的脆性细丝允许一些弹塑性变形，可以启动细丝开裂的可能性。在这里，我们提出了一个ITER环形场（TF）青铜工艺股（在0.4%，0.6%和1%的应变测试）和一个ITER TF内部锡股（在0.4%，0.6%和0.7%的应变测试）的单轴加载循环（0，1000，10,000和30,000个周期）下的灯丝开裂的金相研究。在接近两种股线各自的断裂极限（单轴拉伸载荷下股线断裂的应变）时发现长丝的显著开裂。在0.6%的应变后，青铜工艺股线中的长丝开裂倾向于随着加载循环次数的增加而增加，直到10，000次，然后在加载循环从10，000次增加到30，000次后几乎保持不变。另一方面，内部锡股线显示出随着加载循环增加至10，000直至0.6%应变，长丝开裂增加。对于这两种类型的股线，在所有条件下，裂纹最有可能出现在空隙附近。
In a tokamak, such as ITER, superconducting strands suffer from bending and uniaxial strain due to Lorentz force loading/unloading and thermal cool down which may de- grade the performance over time due to specific cable-in-conduit conductor (CICC) design choice. Under repeated uniaxial loading the Cu(Sn) matrix which surrounds the brittle filaments allows the possibility of some elastic-plastic deformation that can initiate filament cracking. Here we present a metallographic study of filament cracking under increasing uniaxial loading cycles (0, 1000, 10,000 and 30,000 cycles) for one ITER Toroidal field (TF) bronze-process strand (tested at 0.4%, 0.6% and 1% strain) and one ITER TF internal tin strand (tested at 0.4%, 0.6% and 0.7% strain). Significant cracking of filaments was found at close to the respective fracture limits (strain at which strand breaks under uniaxial tensile loading) for both strands. After 0.6% strain, filament cracking in the bronze-process strand tends to increase with increasing number of loading cycles up to 10,000 and then remains almost constant after increasing the loading cycles from 10,000 to 30,000. The internal tin strand on the other hand showed an increase in filament cracking with increasing loading cycles to 10,000 up to 0.6% strain. For both types of strand and in all conditions the cracks were most likely to be found adjacent to voids.