考虑加/卸载速率影响的Ti-Ni形状记忆合金简化本构模型

系统研究了Ti-Ni形状记忆合金丝(SMA)应力-应变曲线、特征点应力、耗能能力、等效阻尼比随材料直径、应变幅值、加载速率、加载循环次数的变化规律;针对SMA唯象Brinson本构模型无法描述SMA动态力学性能的缺点,结合前述试验结果,提出了一种可考虑加/卸载速率影响的SMA简化本构模型。应用该模型对试验用SMA丝进行模拟,所得应力-应变曲线各特征点平均误差仅为3%,结果表明:所建立的速率相关SMA简化本构模型可较为精确地描述SMA在应力诱发相变过程中的超弹性力学行为,同时可反映加/卸载速率和应变幅值等主要因素对其动力本构模型的影响;该模型结构形式简单,具有较好的工程应用前景。

A Simplified Constitutive Model of Ti-Ni Shape Memory Alloy Considering Loading/Unloading Rate

Systematic study was conducted on variation regularity for stress-strain curve, feature points stress, dissipated energy, equivalent damping ratio of Ti-Ni shape memory alloy (SMA) wires changed with diameter of wires, strain amplitude, loa-ding rate and loading cyclic number. Combining with above experimental results, a simplified constitutive model for SMA considering loading/unloading rate was proposed, aiming at making up the disadvantage of phynomenological Brinson constitutive model that cannot describe dynamic mechanical property of SMA. Then, simulation of experimental SMA wires with this constitutive model was conducted. The average errors of feature points in stress-strain curve were only 3%. The results showed the proposed simplified rate-dependent constitutive model of SMA could satisfactorily describe the superelastic mechanical behavior of SMA during the stress-induced transformation, and reflect the influence of dominant factors such as loading/unloading rate and strain amplitude to the dynamic constitutive model. Therefore, with simple formulation, the constitutive model is useful for practical engineering application of SMA.