Basic Study of Electric Generation with Low Temperature Heat Source by Shape Memory Alloy(Thrmo-Mechanical Cyclic Properties and Lengthening of Fatigue Life)

本研究旨在为形状记忆合金(SMA)低温热源发电系统的组成提供基础数据。在将形状记忆合金应用于发电系统的情况下，形状记忆合金是在加载-卸载和加热-冷却相结合的热力机械循环条件下使用的。功能和力学性能的变化，如相变温度、形变应力、回复应力和应变能的增加或降低，以及热机械循环中出现不可恢复应变和双向应变等退化现象。将形状记忆合金应用于发电系统，对于了解形状记忆合金的性能变化和退化特性，延长其疲劳寿命具有重要意义。本研究采用不同冷加工工艺的钛镍铜形状记忆合金丝试件进行…热加工利用已建立的热机疲劳试验设备进行更多的机械循环试验。并通过试验研究了冷加工对形状记忆合金功能性能和疲劳性能的影响。冷加工是延长疲劳寿命的方法之一，冷加工率为10~40%。主要研究结果如下：1.研究结果。随着冷变形率的增加，变形应力增大，各种相变温度降低，回复应力随冷变形率的增大而增大。每周有效应变能随冷加工比的增加而增加。功能退化发生在马氏体相，降解率在较高的冷加工比下趋于稳定。随着冷加工比的增加，热机械循环疲劳的全寿命变短，整个疲劳寿命的总可用应变能随冷加工比的增大而减小。热机械疲劳寿命用离散应变能来评估，该分散应变能被确定为每循环恢复应变能的降低。较少

This research is aming to obtain the basic data for composition of the electric generation system with low temperature heat source by shape memory alloys (SMA). In the case of applying the SMA to the electric generation system, the SMA are used under the conditions of thermo - mechnaical cycling in combining with loading-unloading and heating - cooling. And, the functional and the mechanical properties change such as increase or decrease in the transformation temperature, the derfomation stress, the recovery stress and the strain energy and also, the degradations arise such as appearance of the irrecoverable strain and the two-way strain with thermo-mechanical cycling. It is very ipmortant to know the properties changes and the degradation chnaracteristics, and to make the lengthening of fatigue life of the SMA for appling the SMA to the electric generation system.In this research project, Ti-Ni-Cu type SMA wire specimens with several values of cold-working were used for the thermo-mec … More hanical cyclic tests by using the established thermo-mechnaical fatigue testing equipment.. And the effects of the cold-working on the functional and the fatigue properties of the SMA were investigated experimentally. The cold-working was one of the methods of lengthening of fatigue life, and the conditions of the cold-working ratio were 10〜40%. The results obtained were summarized as the followings.1. The deformation stress increased and the all kinds of transformation temperature decreased with increase in the cold-working ratio, and then, the recovery stress increased with the cold-waoking ratio.2. The available strain energy per cycle increased with increase in the cold-working ratio.3. The functional degradation arised in the martensitic phase, and the the degradated ratio was stabilized in the high cold-working ratio.4. As whole life of the thermo-mechanical cyclic fatigue became shorter with increase in the cold-working ratio, the total available strain energy obtained in the whole fatigue life decreased with increase in the cold-working ratio.5. The themo-mechanical fatigue life was evaluated by the disperted strain enrgy which was determined as the decrease in recovery strain energy per cycle. Less