A comprehensive study of the multiscale homogenized thermal conductivities and thermomechanical properties is conducted towards the filament groups of European Advanced Superconductors (EAS) strand via the recently proposed Multiphysics Locally Exact Homogenization Theory (LEHT). The filament groups have a distinctive two-level hierarchical microstructure with a repeating pattern perpendicular to the axial direction of Nb 3 Sn filament. The Nb 3 Sn filaments are processed in a very high temperature between 600 and 700°C, while its operation temperature is extremely low, −269°C. Meanwhile, Nb 3 Sn may experience high heat flux due to low resistivity of Nb 3 Sn in the normal state. The intrinsic hierarchical microstructure of Nb 3 Sn filament groups and Multiphysics loading conditions make LEHT an ideal candidate to conduct the homogenized thermal conductivities and thermomechanical analysis. First, a comparison with a finite element analysis is conducted to validate effectiveness of Multiphysics LEHT and good agreement is obtained for the homogenized thermal conductivities and mechanical and thermal expansion properties. Then, the Multiphysics LEHT is applied to systematically investigate the effects of volume fraction and temperature on homogenized thermal conductivities and thermomechanical properties of Nb 3 Sn filaments at the microscale and mesoscale. Those homogenized properties provide a full picture for researchers or engineers to understand the Nb 3 Sn homogenized properties and will further facilitate the material design and application.

中文翻译：

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多尺度Nb3Sn灯丝的有效热导率和热机械均化方案

通过最近提出的多物理场局部精确均质化理论（LEHT），对欧洲先进超导体（EAS）股的灯丝组进行了多尺度均质热导率和热机械性能的综合研究。灯丝组具有独特的两级分层微观结构，其重复图案垂直于Nb 3 Sn灯丝的轴向。Nb 3 Sn细丝在600至700°C的极高温度下加工，而其工作温度极低，为-269°C。同时，由于在正常状态下Nb 3 Sn的电阻率低，所以Nb 3 Sn可能经历高热通量。Nb 3 Sn灯丝组的固有层次微观结构和多物理场加载条件使LEHT成为进行均质热导率和热力学分析的理想选择。首先，与有限元分析进行比较以验证Multiphysics LEHT的有效性，并获得均质的热导率以及机械和热膨胀特性的良好一致性。然后，利用多物理场LEHT系统地研究了体积分数和温度对Nb 3 Sn细丝的均相热导率和热机械性能的微观和中观影响。