Thermo-mechanical properties of bulk high Tc, superconductors

1循环热冲击：对从单畴Dy_（123）块材上切下的试样进行了冷却至77 K的110次热冲击后的拉伸试验。虽然杨氏模量E和极限拉伸强度UTS在a、B轴上没有变化，但它们在c轴上下降到一半。在小试样中，未发现UTS和断裂韧性的损伤。热循环略微降低了粘附在钛棒上的样本的UTS。在10wt%的Ag颗粒添加Dy 123本体，E略有下降，UTS增加。颗粒通过在颗粒附近产生残余压应力来防止热损伤，利用ANSYS对快速冷却非稳态热应力进行有限元分析，解释了不同尺寸试样的损伤差异。结果表明，直径增加到100毫米和厚度的散装提高热应力，但它饱和在25毫米的厚度。纯样品a、B轴上的最大热应力较大，而加银样品c轴上的最大热应力较大。这是由于较高的热导率和c轴上的E。2块体-金属复合材料：直接或通过块体夹层粘附到Al和Ti棒的块体试样在77 K下的UTS依次较高。在高热应力区，附着铝的试样发生断裂，而有中间层的试样则没有发生断裂。UTS对应于有限元模拟拉伸试验中的最大应力。3低温热参数：使用我们的传导冷却制冷型系统，热导率和热膨胀系数的温度依赖性相关的大块和金属的热应力下至20 K进行了评估。

1 Cyclic thermal shocks : Tensile tests on the specimens cut from large single domain Dy123 bulk subjected to 110 cycles of thermal shock by cooling to 77K have been conducted. Although the Young's modulus, E, and the ultimate tensile strength, UTS, did not change in a, b axis, they decreased to half in c-axis. In the small specimens, no damage was found in UTS and the fracture toughness. The thermal cycle slightly lowered the UTS of specimen adhered to Ti rod. In the 10wt% Ag particle added Dy123 bulk, E slightly decreased and UTS increased. The particles prevent the thermal damage through the compressive residual stress near the particle.The finite element method analysis, ANSYS, on the non-steady state thermal stress by rapid cooling explained the difference of damage in specimens with different size mentioned above. It was shown that the increase in diameter to 100 mm and thickness of the bulk raise the thermal stress but it saturates at 25 mm thickness. While the maximum thermal stress in a, b axis was larger in plain sample, those in c-axis was larger in Ag added sample. This is due to the higher thermal conductivity and E in c-axis.2 Bulk-metal composite : The UTS at 77K of the bulk specimens adhered directly or via the bulk interlayer to the Al and Ti rods were higher in the order. Although the specimens adhered to Al were broken in the high thermal stress region, it was not the case in specimens with interlayer. The UTS corresponded with the maximum stress in the FEM simulated tensile test.3 Cryogenic thermal parameters : Using our conduction cooling refrigerating type system, the temperature dependence of thermal conductivity and coefficient of thermal expansion relevant to the thermal stress of bulk and metals down to 20K were evaluated.