Microscopic fracture of filaments and its relation to the critical current under bending deformation in (Bi,Pb)2Sr2Ca2Cu3O10 composite superconducting tapes
Microscopic fracture of filaments and its relation to the critical current under bending deformation in (Bi,Pb)2Sr2Ca2Cu3O10 composite superconducting tapes
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DOI：
10.1088/0953-2048/16/9/314
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发表时间：
2003-09
影响因子：
3.6
通讯作者：
M. Hojo;M. Nakamura;T. Matsuoka;Mototsugu Tanaka;Shojiro Ochiai;M. Sugano;K. Osamura
中科院分区：
文献类型：
--
作者：
M. Hojo;M. Nakamura;T. Matsuoka;Mototsugu Tanaka;Shojiro Ochiai;M. Sugano;K. Osamura
研究了（Bi，Pb）_2Sr_2Ca_2Cu_3O_（10）（Bi_（2223））/Ag/Ag？对Mg复合超导带材弯曲变形进行了实验研究和理论分析。对VAMAS弯曲循环试验计划中使用的一种胶带进行了试验。复杂的压力？首先分析了每个部件在拉伸时的应变行为。这是通过比较压力来完成的吗应变曲线的复合带与那些的Ag和Ag？镁合金带。这里，塑性变形（加工硬化）的Ag和Ag？镁合金，并考虑了由于制造过程中的热残余应变。的Bi 2223长丝的断裂应变被逆确定为0.08%，以满足全球拉伸应力？复合带的应变曲线。计算的压力？应变曲线最终与实验结果吻合良好时，供应的弯曲应变被考虑在内。然后，对分析进行了修改，以适应弯曲变形。在这里，运动的中性轴由于非对称和弹性？塑性应力？考虑了构件的应变曲线及其包辛格效应。从断裂细丝的体积分数计算出随着Bi 2223带曲率的增加Ic的相对减小。在考虑中性轴移动和包辛格效应的情况下，计算的Ic与实验结果吻合较好。微观观察表明，当曲率较小时，纤维的损伤发生在拉伸侧的最外层，然后损伤前沿向内层转移。观察到的Bi 2223细丝的断裂行为与基于上述分析的估计位置非常一致。
The strain dependence of the critical current, Ic, of (Bi,Pb)2Sr2Ca2Cu3O10 (Bi2223)/Ag/Ag?Mg composite superconducting tapes has been studied both experimentally and analytically under bending deformation. Tests have been carried out for one type of tape used in the VAMAS bending round-robin programme. The complex stress?strain behaviour of each component was first analysed in tension. This was done by comparing the stress?strain curves of composite tapes with those of Ag and Ag?Mg alloy tapes. Here, the plastic deformation (work hardening) of Ag and Ag?Mg alloy, and the thermal residual strain due to the manufacturing process were taken into account. The fracture strain of Bi2223 filaments was inversely determined as 0.08% to meet the global tensile stress?strain curve of the composite tape. The calculated stress?strain curves finally agreed well with the experimental results when the as-supplied bending strain was taken into account. Then, the analysis was modified to fit the bending deformation. Here, the movement of the neutral axis due to the non-symmetric and elastic?plastic stress?strain curves of the components and their Bauschinger effect were taken into account. The relative decrease of Ic with the increase in the Bi2223 tape curvature was calculated from the volume fraction of the broken filaments. The calculated Ic agreed well with the experimental results when the movement of the neutral axis and the Bauschinger effect were taken into account. Microscopic observation of the spatial distribution of the filament fracture indicated that the damage occurred at the outermost layer on the tensile side when the curvature was small, and then the damage front shifted to the inside layers. The observed fracture behaviour of the Bi2223 filament agreed well with the estimated location based on the above analysis.