Macroscopic modeling of strain-rate dependent energy dissipation of superelastic SMA dampers considering destabilization of martensitic lattice
Macroscopic modeling of strain-rate dependent energy dissipation of superelastic SMA dampers considering destabilization of martensitic lattice
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DOI：
10.1088/1361-665x/ab5e42
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发表时间：
2020-02-01
影响因子：
4.1
通讯作者：
Klinkel, S.
中科院分区：
文献类型：
--
作者：
Kaup, A.;Altay, O.;Klinkel, S.
超弹性形状记忆合金是一种独特的智能材料，在变应变率动态载荷下具有相当大的能量耗散潜力。能量耗散来自于多晶原子网格结构的滞后相变。事实上，从奥氏体到马氏体相以及从马氏体到奥氏体的形核表现出强烈的热机械耦合。滞后取决于奥氏体-马氏体转变产生的潜热以及该热量的对流。由于热机械耦合，马氏体形核应力水平以及因此马氏体相锋的传播强烈地依赖于材料温度。高应变率影响相变潜热向环境的释放，决定马氏体相变带的数量、位置和扩展。最后，高应变率减小了滞后面。马氏体带的传播速度和数量对马氏体相的稳定性有影响。原子无序程度和相应的熵变化影响马氏体到奥氏体的逆相变。换句话说，马氏体状态的稳定性影响逆相变的应力水平。然而，在用于模拟能量耗散行为的唯象超弹性SMA模型中，没有特别考虑率相关熵变的影响。为了纳入率相关的熵变，我们改进了一个一维的数值模型，通过引入一个额外的控制变量的自由能配方的超弹性SMA的固-固相变。在该模型中，通过计算率相关熵变，考虑了应变率对逆相变的影响。数值计算结果与实验结果的比较表明，该模型能更准确地计算SMA的动态超弹性滞回。
Superelastic shape-memory alloys (SMAs) are unique smart materials with a considerable energy dissipation potential for dynamic loadings with varying strain-rates. The energy dissipation arises from a hysteretic phase transformation of the polycrystalline atomic grid structure. In fact, the nucleation from austenite to martensite phase and vice versa exhibits a strong thermomechanical coupling. The hysteresis depends on the latent heat generated by the austenitic-martensitic transformation and the convection of that heat. Due to the thermomechanical coupling, the martensitic nucleation stress level and thus the propagation of martensitic phase fronts strongly depends on the material temperature. High strain-rate interferes with the release of the latent heat to the environment and determines quantity, position and propagation of martensitic transformation bands. Lastly, high strain-rate reduces the hysteresis surface. The propagation velocity and quantity of martensitic bands have an impact on martensitic phase stability. The degree of atomic disorder and accordingly the change in entropy influences the reverse phase transformation from martensite to austenite. In other words, the stability of the martensitic state affects the stress level of the reverse transformation. However, in phenomenological superelastic SMA models, which are used to simulate energy dissipation behavior, the effects of the rate-dependent entropy change are not considered in particular. To incorporate the rate-dependent entropy change, we improved a one-dimensional numerical model by introducing an additional control variable in the free energy formulation for solid-solid phase transformation of superelastic SMAs. In this model, the observed effects of the strain-rate on the reverse transformation are taken into account by calculating the rate-dependent entropy change. A comparison of the numerical results with the experimental data shows that the model calculates the dynamic superelastic hysteresis of SMAs more accurately.