The rate dependence of transformation pattern in superelastic NiTi tube (diameter-wall thickness ratio is 10) under uniaxial tension is investigated numerically. Simulations and experiments show that mechanical instability upon martensitic transformation is manifested as inhomogeneous deformation and stress plateau. As strain rate increases, the stress plateau converts from the horizontal type to the hardening one and the transformation band transits from cylinder to helix. The rate dependence of transformation pattern originates from the contest between the mechanically favorable cylindrical band and the thermomechanically favorable helical band. The results are inspiring to unveil the rate effect of mechanical instability in phase transformable material.

数值研究了单轴拉伸下超弹性NiTi管（壁厚比为10）中相变模式的速率依赖性。仿真和实验表明，马氏体相变后的机械不稳定性表现为不均匀变形和应力平稳。随着应变率的增加，应力平台从水平型转变为硬化型，而转变带则从圆柱型转变为螺旋型。转变模式的速率依赖性源自机械上有利的圆柱带和热机械上有利的螺旋带之间的竞争。结果令人鼓舞，揭示了相变材料中机械不稳定性的速率效应。