高温超导带材低/变温疲劳性能测试系统的研制

实用化高温超导带材(如Bi系与ReBCO高温超导复合带材)在高磁场下拥有较高的临界电流密度、宽泛的温度裕度、较强的抗粒子辐照能力及良好的机械特性，因此这类材料在加速器超导磁体系统、高场超导磁体、超导电力等方面表现出巨大的应用潜力。而作为典型的多层功能复合性材料，虽然高强度的基底层增强了高温超导带材拉伸强度，使其在强磁场、高载流条件下可以承受很高的应力，在其加工与运行过程中，不可避免地受到多种疲劳载荷的作用，从而其临界载流能力会显著地降低，进一步，会造成相应高温超导装置功能性难以达到设计标准等。该文介绍一种自主研制的高温超导带材低/变温疲劳性能测试系统，基于该测试系统:一方面，可以实现对高温超导材料在低/变温、疲劳载荷等环境下力学、热学等宏观参数的实验表征研究；另一方面，可以对高温超导材料开展低温疲劳载荷环境下力-电弱化等临界特性的实验研究。利用所研制的低/变温疲劳性能测试系统，对受拉-压疲劳荷载下的YBCO超导带材的力学行为、载流特性开展了初步的实验研究，并分析了应力比、温度等外部环境因素对实验结果的影响规律等。结果表明:在相同的疲劳次数的情况下，YBCO超导带材的力学性能及载流特性与其应力比成明显的非线性关系。该测试系统的成功研制将为中国粒子加速器用高温超导磁体的设计与研发提供基础测试平台。

DEVELOPMENT OF A CRYOGENIC FATIGUE TEST FACILITY FOR HIGH TEMPERATURE SUPERCONDUCTING TAPES

Because of the high critical current density in the intense magnetic field, wider temperature margin, resistance irradiation and good mechanical properties, high temperature superconducting tapes (BSCCO and ReBCO taps) have a huge potential application in accelerator magnets, high field magnets and superconducting electric power systems. Some expectable opportunities will be created for modern high-tech electromagnetic equipment. High temperature superconducting tapes with substrate layers usually have high tensile strength. Thus, they can be applied under an intense electromagnetic field. However, in its application process and under the operation conditions, many kinds of inevitable fatigue loads will occur, which have an impact on the current-carrying capacity of the high temperature superconducting tapes and can destroy the high temperature superconducting magnets. A cryogenic fatigue test facility for high temperature superconducting tapes is introduced, the system can be used to measure the mechanical, thermal and strain-field-dependent behaviors of fatigued superconducting wires and tapes under variable cryogenic temperatures. Based on the cryogenic fatigue test facility, the mechanical behaviors and current-carrying characteristics of tension-compression fatigued YBCO tapes were experimentally studied. The preliminary test results show that their mechanical behaviors and current-carrying characteristics showed a nonlinear dependence on the stress ratio during the fatigue test. The successful development of the cryogenic fatigue test facility will provide a basic fatigue test platform for the design and development of accelerator high temperature superconducting magnets.