NiTi形状记忆合金裂纹尖端热力耦合行为研究

Numerical Simulation of Thermomechanical Coupling Behavior at Crack Tip of NiTi Shape Memory Alloy

论文对NiTi形状记忆合金I型裂纹尖端热力耦合行为进行了数值仿真分析和实验验证.建立了包含相变和热力耦合的本构模型,通过有限元计算得到了裂纹尖端附近的纵向应变、马氏体体积分数和温度场分布,依据马氏体相变情况对裂纹尖端有效应力强度因子进行了修正,揭示了加载速率对形状记忆合金裂纹尖端有效应力强度影子的影响规律.参数研究表明,随着加载频率的增加,裂纹尖端附近温度逐渐升高,马氏体相变区域逐渐缩小,有效应力强度因子呈下降趋势,形状记忆合金表现出增韧效应,有助于减缓裂纹扩展.该研究结果对于揭示热力耦合作用下超弹性形状记忆合金疲劳裂纹扩展规律具有重要参考意义.

The effect of thermomechanical coupling on the stress intensity factor of NiTi shape memory alloys was systematically studied through numerical simulation of the thermomechanical coupling behavior at the mode I crack tip.Firstly,the longitudinal strain distribution,temperature field distribution and martensite volume fraction distribution near the crack tip are calculated using the Z-M constitutive model considering thermomechanical coupling.Then the formula for the effective stress intensity factor of shape memory alloys is modified according to the martensitic transformation.The effective stress intensity factors of shape memory alloys at different loading frequencies are calculated by combining the results of martensitic transformation distribution of finite element simulation with the modified model of effective stress intensity factor,and the effect of loading frequency on the effective stress intensity factor at the crack tip of shape memory alloys are thus revealed.It is found that with the increase of loading frequency,the temperature near the crack tip gradually increases,the martensitic transformation region gradually decreases,and the effective stress intensity factor decreases.This means that increasing the loading frequency has a toughening effect on the shape memory alloy,which is helpful for slowing down the crack growth.The results are of important reference significance for revealing the fatigue crack growth law of pseudoelastic shape memory alloys under thermomechanical coupling effect.