發(fā)布時(shí)間：2018-06-13 06:11

  本文選題：超彈性鎳鈦合金 + 熱-力耦合�。� 參考：《西南交通大學(xué)》2015年碩士論文

【摘要】：超彈性鎳鈦合金作為倍受關(guān)注的新型智能材料,在實(shí)際工程應(yīng)用中必然會(huì)受到不同頻率的循環(huán)載荷作用。已有的研究表明超彈性鎳鈦合金存在率效應(yīng),然而在循環(huán)變形過(guò)程中,由熱-力耦合所引起的材料率相關(guān)性的研究還比較欠缺。本文對(duì)超彈性鎳鈦合金的單軸熱-力耦合循環(huán)變形行為進(jìn)行了實(shí)驗(yàn)研究和本構(gòu)描述,主要研究工作如下：1、實(shí)驗(yàn)研究：(1)在3.3×10-4/s-3.3×10-2/s的范圍內(nèi)對(duì)超彈性鎳鈦合金微管進(jìn)行了單軸循環(huán)變形實(shí)驗(yàn)。對(duì)不同應(yīng)變率下的循環(huán)變形行為進(jìn)行了分析。結(jié)果顯示：循環(huán)過(guò)程中的內(nèi)部熱效應(yīng)在不同加載速率下展現(xiàn)出不同的溫升；循環(huán)變形同時(shí)也誘發(fā)了相變硬化現(xiàn)象：存在一個(gè)臨界應(yīng)變率,耗散能在其上下展現(xiàn)非單調(diào)關(guān)系。(2)在1MPa/s～80MPa/s的范圍內(nèi)對(duì)超彈性鎳鈦合金微管進(jìn)行了軸向不同應(yīng)力率下的相變棘輪行為實(shí)驗(yàn)。結(jié)果表明：與應(yīng)變率循環(huán)變形實(shí)驗(yàn)一樣,材料同樣受到熱-力耦合作用,表現(xiàn)出率相關(guān)性。相同的應(yīng)力水平下,應(yīng)力率越大,材料的相變棘輪應(yīng)變?cè)矫黠@,耗散能越小。(3)20℃～120℃環(huán)境溫度下的應(yīng)變循環(huán)實(shí)驗(yàn)和應(yīng)力循環(huán)實(shí)驗(yàn)表明：循環(huán)變形過(guò)程中,相變應(yīng)力和逆相變應(yīng)力隨著環(huán)境溫度的升高而增大,在80℃以內(nèi)滿足線性增加的關(guān)系；環(huán)境溫度超過(guò)80℃會(huì)導(dǎo)致相變應(yīng)力和逆相變應(yīng)力與溫度的關(guān)系發(fā)生線性偏離；溫度越高,殘余應(yīng)變和相變棘輪應(yīng)變演化越迅速。2、本構(gòu)模型研究：(1)基于Graesser模型,引入循環(huán)變形過(guò)程中向前相變應(yīng)力和逆相變應(yīng)力以及殘余應(yīng)變的演化方程,將模型擴(kuò)展成描述超彈性鎳鈦合金相變誘發(fā)塑性的率無(wú)關(guān)循環(huán)本構(gòu)模型；在此基礎(chǔ)上,引入率相關(guān)演化參數(shù),進(jìn)一步建立考慮相變誘發(fā)塑性的率相關(guān)循環(huán)本構(gòu)模型,通過(guò)與實(shí)驗(yàn)結(jié)果的對(duì)比驗(yàn)證了模型的合理性。(2)在熱力學(xué)框架下對(duì)相變過(guò)程中馬氏體體積分?jǐn)?shù)演化方程進(jìn)行改進(jìn),考慮了材料本征機(jī)械耗散散和相變潛熱兩種內(nèi)部熱效應(yīng)機(jī)制,引入內(nèi)應(yīng)力演化方程來(lái)反映循環(huán)變形過(guò)程相變應(yīng)力的衰減,引入相變誘發(fā)塑性機(jī)制來(lái)反映殘余應(yīng)變的循環(huán)累積,建立了描述超彈性鎳鈦合金熱-力耦合行為的循環(huán)本構(gòu)模型,對(duì)實(shí)驗(yàn)的應(yīng)力-應(yīng)變曲線和溫度演化進(jìn)行模擬,驗(yàn)證了模型的合理性。
[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，

本文編號(hào)：2013011