Elastocaloric effect vs fatigue life: Exploring the durability limits of Ni-Ti plates under pre-strain conditions for elastocaloric cooling
Elastocaloric effect vs fatigue life: Exploring the durability limits of Ni-Ti plates under pre-strain conditions for elastocaloric cooling
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DOI：
10.1016/j.actamat.2018.03.032
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发表时间：
2018-05-15
期刊：
影响因子：
9.4
通讯作者：
Cadelli, Andrea
中科院分区：
文献类型：
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作者：
Tusek, Jaka;Zerovnik, Andrej;Cadelli, Andrea
结构疲劳是阻止弹性热效应（eCE）在冷却或热泵装置中实际应用的主要障碍。在这里，镍钛板的eCE和疲劳行为进行了系统的研究，以确定疲劳应变极限和相关的eCE。最初，eCE进行了评估，通过测量绝热温度变化，在不同的应变幅度和不同的平均应变沿着加载和卸载的转变平台。通过比较具有和不具有预应变条件的eCE，证明了在转变平台中部附近的平均应变下循环弹性热材料的优点。在本工作的第二部分中，我们分别评估了在初始预应变高达6%和10%后，在加载平台和卸载平台处的平均应变为2.25%的疲劳寿命。结果表明，在抛光样品上，在加载平台处的应变幅度为0.50%时，可以达到10（5）个循环的耐久性操作。其对应于约5K的绝热温度变化。在卸载平台（在10%的初始预应变之后），在1.00%的应变幅度下达到持久操作，对应于约8K的绝热温度变化。在循环后分析功能疲劳，结果表明，一旦样品稳定，即使在10（5）次循环后，eCE也没有进一步降解。这些结果为将来设计和操作高效耐用的弹性热装置提供了指导。(C)2018 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
Structural fatigue is the major obstacle that prevents practical applications of the elastocaloric effect (eCE) in cooling or heat-pumping devices. Here, the eCE and fatigue behaviour of Ni-Ti plates are systematically investigated in order to define the fatigue strain limit and the associated eCE. Initially, the eCE was evaluated by measuring adiabatic temperature changes at different strain amplitudes and different mean strains along the loading and unloading transformation plateaus. By comparing the eCE with and without pre-strain conditions, the advantages of cycling an elastocaloric material at the mean strain around the middle of the transformation plateau were demonstrated. In the second part of this work, we evaluated the fatigue life at the mean strain of 2.25% at the loading plateau and at the unloading plateau after initial pre-straining up to 6% and 10%, respectively, It is shown that on polished samples, durable operation of 10(5) cycles can be reached with a strain amplitude of 0.50% at the loading plateau, which corresponds to adiabatic temperature changes of approximately 5 K. At the unloading plateau (after initial pre-strain of 10%), durable operation was reached at a strain amplitude of 1.00%, corresponding to adiabatic temperature changes of approximately 8 K. The functional fatigue was analysed after the cycling and it is shown that once the sample has been stabilized there is no further degradation of the eCE, even after 10(5) cycles. These results present guidelines for the design and operation of efficient and durable elastocaloric devices in the future. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.