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中文核心期刊

带孔形状记忆合金薄板弹热性能的实验和理论研究

ELASTOCALORIC PERFORMANCE OF SHAPE MEMORY ALLOY THIN PLATES WITH HOLES: EXPERIMENTAL OBSERVATION AND THEORETICAL MODELING

  • 摘要: NiTi形状记忆合金因其优异的弹热效应在新兴固态制冷领域具备广阔的应用前景. 然而, 该类合金较高的相变临界应力使得其弹热效应需要很高的机械载荷来驱动, 对固态制冷器件的小型化和大规模应用带来了挑战. 文章通过在NiTi形状记忆合金薄板上引入孔洞, 揭示了孔洞体积分数、分布形式对薄板弹热性能的影响. 结果表明, 孔洞造成的应力集中效应能够在显著降低薄板相变驱动力的同时, 有效增加薄板的整体制冷温度和吸热量. 薄板在变形过程中的整体力-位移响应和温度演化强烈依赖于孔洞体积分数, 孔洞分布形式仅仅影响薄板的局部应力-应变-温度场, 而对整体的热-力响应影响较小. 进一步地, 基于应力对数客观率, 在不可逆热力学框架下建立了形状记忆合金有限变形热-力耦合本构模型, 并完成了模型的有限元移植. 通过与实验结果的对比发现, 提出的本构模型能够很好地预测孔洞对NiTi形状记忆合金薄板变形行为和弹热性能的影响, 从而为该类合金带孔薄板的设计提供理论工具.

     

    Abstract: NiTi shape memory alloy has a wide application prospect in the emerging field of solid-state refrigeration due to its excellent elastocaloric performance. However, the high critical stress of martensite transformation requires a high driving force to trigger the elastocaloric effect. It brings a challenge to the miniaturization and large-scale application of the solid-state refrigeration devices made by NiTi shape memory alloy. To overcome this shortcoming, NiTi shape memory alloy thin plates with holes are employed in this work. The effects of hole volume fraction and hole distribution form on the elastocaloric effect of the thin plates are revealed. Experimental results indicate that the stress concentration effect caused by the holes can significantly reduce the driving force of martensite transformation, and effectively increase the overall cooling temperature of the thin plates. During deformation, the overall force-displacement response and temperature evolution of the thin plates depend on the hole volume fraction strongly. However, the distribution form of the holes only affects the local stress, strain and temperature fields, but plays a minor role in the overall thermo-mechanical responses. Based on the logarithmic stress rate, a finite deformation thermo-mechanically coupled constitutive model of shape memory alloys is established within the framework of irreversible thermodynamics. The proposed model is further implemented into the finite element program. By comparing the predicted results with the experimental ones, it can be found that the proposed model can effectively predict the effect of holes on the deformation behavior and elastocaloric performance of NiTi shape memory alloy thin plates. This work provides a theoretical guidance to design and assess the refrigeration device manufactured by shape memory alloy thin plates.

     

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