超弹性镍钛合金单轴热—力耦合循环变形行为及其本构描述

发布时间：2018-06-13 06:11

  本文选题：超弹性镍钛合金 + 热-力耦合　； 参考：《西南交通大学》2015年硕士论文

【摘要】：超弹性镍钛合金作为倍受关注的新型智能材料,在实际工程应用中必然会受到不同频率的循环载荷作用。已有的研究表明超弹性镍钛合金存在率效应,然而在循环变形过程中,由热-力耦合所引起的材料率相关性的研究还比较欠缺。本文对超弹性镍钛合金的单轴热-力耦合循环变形行为进行了实验研究和本构描述,主要研究工作如下：1、实验研究：(1)在3.3×10-4/s-3.3×10-2/s的范围内对超弹性镍钛合金微管进行了单轴循环变形实验。对不同应变率下的循环变形行为进行了分析。结果显示：循环过程中的内部热效应在不同加载速率下展现出不同的温升；循环变形同时也诱发了相变硬化现象：存在一个临界应变率,耗散能在其上下展现非单调关系。(2)在1MPa/s～80MPa/s的范围内对超弹性镍钛合金微管进行了轴向不同应力率下的相变棘轮行为实验。结果表明：与应变率循环变形实验一样,材料同样受到热-力耦合作用,表现出率相关性。相同的应力水平下,应力率越大,材料的相变棘轮应变越明显,耗散能越小。(3)20℃～120℃环境温度下的应变循环实验和应力循环实验表明：循环变形过程中,相变应力和逆相变应力随着环境温度的升高而增大,在80℃以内满足线性增加的关系；环境温度超过80℃会导致相变应力和逆相变应力与温度的关系发生线性偏离；温度越高,残余应变和相变棘轮应变演化越迅速。2、本构模型研究：(1)基于Graesser模型,引入循环变形过程中向前相变应力和逆相变应力以及残余应变的演化方程,将模型扩展成描述超弹性镍钛合金相变诱发塑性的率无关循环本构模型；在此基础上,引入率相关演化参数,进一步建立考虑相变诱发塑性的率相关循环本构模型,通过与实验结果的对比验证了模型的合理性。(2)在热力学框架下对相变过程中马氏体体积分数演化方程进行改进,考虑了材料本征机械耗散散和相变潜热两种内部热效应机制,引入内应力演化方程来反映循环变形过程相变应力的衰减,引入相变诱发塑性机制来反映残余应变的循环累积,建立了描述超弹性镍钛合金热-力耦合行为的循环本构模型,对实验的应力-应变曲线和温度演化进行模拟,验证了模型的合理性。
[Abstract]:As a new intelligent material, superelastic Ni-Ti alloy is bound to be subjected to cyclic loading at different frequencies in practical engineering applications. The existing studies have shown that there exists a rate effect in superelastic Ni-Ti alloys, but in the process of cyclic deformation, the dependence of material rate caused by thermal-mechanical coupling is still lacking. In this paper, the uniaxial thermal-mechanical cyclic deformation behavior of superelastic nickel-titanium alloy is studied experimentally and its constitutive model is described. The main research work is as follows: (1) the uniaxial cyclic deformation experiments of superelastic Ni-Ti alloy microtubules were carried out in the range of 3.3 脳 10-4/s-3.3 脳 10 ~ (-2) / s. The cyclic deformation behavior at different strain rates is analyzed. The results show that the internal thermal effect in the cycle shows different temperature rise at different loading rates, and cyclic deformation also induces the phenomenon of phase transformation hardening: there is a critical strain rate, The dissipation energy shows a nonmonotone relationship between the upper and lower layers. (2) the ratcheting behavior of superelastic nickel-titanium alloy microtubules at different axial stress rates has been investigated in the range of 1 MPA / s ~ (80) MPA / s. The results show that, as in the strain rate cyclic deformation experiment, the material is also subjected to thermal-mechanical coupling, showing a rate-dependent relationship. At the same stress level, the larger the stress rate, the more obvious the ratchet strain of the material is, and the smaller the dissipation energy is, the smaller the strain cycling and stress cycling experiments are at 20 鈩，

本文编号：2013011