Certain shape memory alloys (SMAs) are considered to be good absorbents of hydrogen atoms (e.g., NiTi). However, upon the absorption of hydrogen atoms, SMAs exhibit deteriorated effects of superelasticity and shape memory mechanisms. In this paper, we have developed a coupled model, based on experimental results, that demonstrates the effects of hydrogen diffusion on NiTi SMAs. The proposed model has been derived thermodynamically while appending the chemical potential of hydrogen to the energy balance law. The effects of hydrogen distribution on the mechanical behavior have been taken into consideration to simulate the ageing effects. Moreover, the model considers the saturation of transformation stress, the preservation of the transformation strain of the hydrogen-induced residual martensite and the recovery of superelasticity after hydrogen desorption. The model has been simulated by means of UMAT and UMATHT subroutines and ABAQUS finite-element software. The numerical results indicate a strong agreement with the experimental ones.

中文翻译：

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考虑氢扩散和时效的 NiTi 合金的耦合扩散-力学模型

某些形状记忆合金（SMA）被认为是氢原子的良好吸收剂（例如，NiTi）。然而，在吸收氢原子后，SMA 表现出超弹性和形状记忆机制的劣化效果。在本文中，我们基于实验结果开发了一个耦合模型，该模型展示了氢扩散对 NiTi SMA 的影响。所提出的模型是通过热力学推导出来的，同时将氢的化学势附加到能量平衡定律中。已经考虑了氢分布对机械行为的影响，以模拟老化效应。此外，该模型考虑了转变应力的饱和，氢致残余马氏体相变应变的保持和氢解吸后超弹性的恢复。该模型已通过 UMAT 和 UMATHT 子程序以及 ABAQUS 有限元软件进行了模拟。数值结果表明与实验结果有很强的一致性。