Temperature Superconducting Tapes and Wires

9713433 Ahzi高温超导带材和线材的机械加工通过：(1)发展压实高温超导粉末弹塑性响应的高级细观力学模型，并特别应用于铋基氧化物(BSCCO)；以及(2)实施这些模型来模拟用于制造超导带材和线材的管内氧化物粉末(OPIT)工艺的拉丝和卷带和压制。由于缺乏对粉末氧化物致密化过程中的机械响应的了解，目前用OPIT工艺生产的具有最佳机械和电传输性能的BSCCO超导体(带材和线材)的制造受到限制。在该项目下，开发了用于模拟和设计先进加工方法的预测工具，以生产具有最佳性能的长电线和带材。建立了与孔隙率模型完全耦合的基于物理的多晶基质模型。这些模型基于率相关塑性，具有预测塑性变形过程中织构演化和材料相对密度演化的独特能力。对于超导体，机械性能和最重要的电学性能都强烈地依赖于最终织构、相对密度和微裂纹的存在。因此，能够耦合织构、孔隙率和微裂纹效应的基于物理的材料模型可以更好地理解这些材料在机械加工过程中的力学响应。用细观力学模型研究了两相复合带材(银套BSCCO)轧制过程中超导磁芯截面积上的不一致性(不稳定性)现象，该模型考虑了超导磁芯中微裂纹引起的孔洞、织构硬化(锁定)和弱化现象。将建模和计算工作扩展到模拟多丝超导体的制备。***

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. ***