Temperature Superconducting Tapes and Wires

高温超导带和导线的机械加工是通过以下方式建模的：(1)发展了致密高温超导粉末弹塑性响应的先进微观力学模型，特别是应用于Bi基氧化物（BSCCO）；(2)利用这些模型模拟制备超导带和超导线的管内氧化粉末（OPIT）工艺的拉丝和滚压过程。由于缺乏对粉末氧化物致密化过程中机械响应的理解，OPIT工艺生产的具有最佳机械和电传输性能的BSCCO超导体（带和线）的制造目前受到限制。该项目开发了用于模拟和设计先进加工方法的预测工具，用于生产具有最佳性能的长导线和磁带。建立了与孔隙度模型完全耦合的多晶基质物理模型。这些模型基于速率依赖塑性，具有预测塑性变形过程中织构演变和材料相对密度演变的独特能力。对于超导体来说，机械性能和最重要的电性能都强烈依赖于最终的结构、相对密度和微裂纹的存在。因此，基于物理的材料模型能够耦合织构、孔隙和微裂纹效应，从而更好地理解这些材料在机械加工过程中的力学响应。采用微观力学模型研究了两相复合材料工件（ag -护套BSCCO）轧制过程中超导带芯截面积不一致（不稳定）的现象，该现象考虑了超导带芯的孔隙、织构硬化（锁紧）和微裂纹导致的弱化。将建模和计算工作扩展到模拟多丝超导体的制造。* * *

9713433 Ahzi The mechanical processing of high temperature superconducting tapes and wires is modeled by: (1) developing advanced micromechanical modeling of the elastic- plastic response of compacted high temperature superconducting powders with particular applications to Bi- based oxides (BSCCO); and (2) implementing these models to simulate wire drawing and tape rolling and pressing of the oxide-powder-in-tube (OPIT) process for the fabrication of superconductina tapes and wires. The fabrication of the BSCCO superconductors (tapes and wires) produced by the OPIT process with optimal mechanical and electrical transport properties is currently limited due to the lack of understanding of the mechanical response during the densification of powder oxides. Predictive tools for the simulation and design of advanced processing methodologies for producing long wires and tapes with optimal properties are developed under this project. Physically-based models for the polycrystalline matrix fully coupled with the porosity modeling are developed. These models are based on rate-dependent plasticity and have the unique ability to predict the evolution of texturing during plastic deformation and the evolution of the relative density of the materials. For superconductors, both mechanical and most importantly electrical properties are strongly dependent on the the final texture, relative density, and on the presence of microcracks. Therefore, physically-based material models with the ability of coupling the texturing, porosity and microcracking effects provide a better understanding of the mechanical response during mechanical processing of these materials. The phenomenon of non-conformity (instability) in the sectional area of the superconducting core of rolled tapes, inherent to the rolling of two-phase composite workpiece (Ag-sheathed BSCCO) is studied using micromechanical models which account for the porosity, textural hardening (locking), and weakening due to micr ocracking in the superconducting core. The modeling and computational efforts are extended to simulate fabrication of multifilamentary superconductors. ***