超弹性形状记忆合金管单向拉伸试验的数值模拟

Numerical Simulation for Tension Experiment ofSuperelastic Shape Memory Alloys Tube

NiTi形状记忆合金具有很强的超弹性行为,这种超弹性行为是由于材料在应力作用下发生可逆的马氏体相变所引起。最近Sun和Lee[4]在NiTi形状记忆合金管单向拉伸试验中观测到,应力诱导马氏体相变具有螺旋带状的形貌特征,本文对此作了数值模拟研究。采用包含应变软化效应的三线性本构关系,建立了NiTi形状记忆合金管的三维有限元模型。通过迭代计算,成功地再现了试验中所观察到的螺旋状相变带从形成到长大的全过程。数值计算结果表明,产生这一独特现象的力学机制,在于NiTi形状记忆合金管在拉伸状态下出现的局部变形失稳极其传播。

NiTi shape memory alloys exhibit strong superelastic behavior, which is associated with the reversible martensitic phase transformation. The stress induced martensite transformation in NiTi shape memory alloys tube under uniaxial tension has been observed to proceed in a spiral band pattern by Sun and Lee^[4] recently. The numerical simulation was presented to investigate the phenomenon. The nucleation and the growth of spiral martensite band were successfully reproduced by using the nonlinear finite element method with tri-linear constitutive law including strain soften effects. The results demonstrate that the local deformation instability and its propagation contribute to the mechanism of observed phenomenon in NiTi tube tension.