Strain rate effects on the localization of the stress-induced martensitic transformation in pseudoelastic NiTi under uniaxial tension, compression and compression-shear
Strain rate effects on the localization of the stress-induced martensitic transformation in pseudoelastic NiTi under uniaxial tension, compression and compression-shear
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DOI：
10.1016/j.msea.2015.07.039
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发表时间：
2015-09-03
期刊：
影响因子：
6.4
通讯作者：
Wagner, M. F. -X.
中科院分区：
文献类型：
--
作者：
Elibol, C.;Wagner, M. F. -X.
应力诱导马氏体相变的成核和传播的马氏体带的本地化是众所周知的在伪弹性NiTi形状记忆合金受到拉伸载荷，但是，压缩载荷，是与一个更均匀的变形。在本研究中，我们研究了在10（-4）s（-1）到10（-3）s（-1）范围内的不同应变速率对伪弹性NiTi棒试样的热机械行为的影响，以及在单轴拉伸、单轴简单压缩和一种特殊类型的压剪复合载荷下关于局部化转变的变形模式。动态压缩加载是使用一个专门设计的落塔装置（类似于10（2）s（-1））和一个分离式霍普金森压杆（类似于10（3）s（-1））与脉冲整形器。在准静态和动态实验过程中，为了表征马氏体带的形成和生长，用数字图像相关原位技术系统地记录了表面应变场。相变应力和应力-应变曲线的斜率随应变速率的增加而增加，这可以归因于自加热效应。在高应变率下，应力诱发马氏体相变过程中会形成多个带。在简单压缩下，变形过程均匀，没有明显的应变局部化，变形模式几乎不受应变速率的影响。在压剪复合加载下，由于特殊的试样几何形状，叠加的剪切应力导致即使在高应变率下也会发生局部化转变。我们的研究结果提供了新的见解低/高应变率的相互作用，自加热的材料和相变应力，以及它们的本地化现象和热机械行为的伪弹性NiTi在各种负载情况下的影响。(C)2015 Elsevier B. V.版权所有。
Localization of the stress-induced martensitic transformation by nucleation and propagation of martensite bands is well-known in pseudoelastic NiTi shape memory alloys subjected to tensile loading; compressive loading, however, is associated with a more homogeneous deformation. In this study, we investigate the effect of different strain rates in the range from 10(-4) s(-1) to 10(-3) s(-1) on the thermo-mechanical behavior of pseudoelastic NiTi bar specimens and on the deformation mode with respect to localized transformation under uniaxial tension, uniaxial simple compression, and a special type of combined compression-shear loading. Dynamic compressive loading is performed using a specially designed drop tower setup (epsilon similar to 10(2) s(-1)) and a split Hopkinson pressure bar (epsilon similar to 10(3) s(-1)) with a pulse shaper. Surface strain fields are documented systematically with a digital image correlation in situ technique during both quasi-static and dynamic experiments in order to characterize the formation and growth of martensite bands. The transformation stress and the slopes of the stress-strain curves in the transformation region increase with increasing strain rate for all load cases, which can be attributed to self-heating effects. Multiple bands are formed during the stress-induced martensitic transformation at higher strain rates under uniaxial tension. Under simple compression, the deformation proceeds homogeneously without distinct strain localization and the deformation mode is hardly affected by an increase of the strain rate. Under combined compression-shear loading, the superimposed shear-stresses due to the special specimen geometry result in localized transformation even under high strain rates. Our results provide new insights into the interaction of low/high strain rates, self-heating of the material and transformation stresses, and their effect on localization phenomena and thermo-mechanical behavior of pseudoelastic NiTi in a wide variety of load cases. (C) 2015 Elsevier B.V. All rights reserved.