Multifilamentary Bi₂Sr₂CaCu₂O_x (Bi2212) composite wires are the only high-temperature superconducting round wires (RWs) with sufficient critical current density (J_c) for superconducting magnets generating magnetic fields greater than 25 T. Previous works indicated that various voids in Bi2212 filaments and bridges between the adjacent Bi2212 filaments in Bi2212 RWs were generated after heat treatment. Such complicated microstructural structure will inevitably affect its electrical behavior. Previous studies only focus on single microstructural feature, voids or bridges. Hence, we developed a numerical model containing both voids and bridges to explore the comprehensive influence of these two microstructural features. Due to the preliminary results, it shows that the E-J relationships of the models with bridges and with infinity bridges are similar in the case of numerous bridges between filaments. It indicated that we can build a simplified geometry structural model by removing all the bridges and bonding the adjacent filaments directly. And then the parametric study of the voids was carried out and the results explained that the height (diameter) of void is the key factor to dominant its electrical behavior.

复丝Bi ₂ Sr ₂ CaCu ₂ O _x（Bi2212）复合线是唯一具有足够的临界电流密度（J _c的高温超导圆线（RW））产生大于25 T的磁场的超导磁体。先前的工作表明，Bi2212灯丝中的各种空隙以及Bi2212 RW中相邻的Bi2212灯丝之间的桥接是在热处理后产生的。这种复杂的微结构不可避免地会影响其电学行为。以前的研究仅关注单个微结构特征，空隙或桥梁。因此，我们开发了一个包含空隙和桥梁的数值模型，以探索这两个微观结构特征的综合影响。由于初步结果，它表明EJ在细丝之间存在许多桥的情况下，模型与桥和无限桥的关系相似。这表明我们可以通过删除所有桥并直接粘合相邻的细丝来构建简化的几何结构模型。然后对空隙进行了参数研究，结果说明空隙的高度（直径）是决定其电学行为的关键因素。