本文關(guān)鍵詞： NiTi形狀記憶合金 功能性劣化 熱力耦合 本構(gòu)模型 宏觀 細(xì)觀　出處：《西南交通大學(xué)》2015年博士論文　論文類型：學(xué)位論文

【摘要】：NiTi形狀記憶合金以其優(yōu)越的超彈性、形狀記憶特性、生物相容性以及高阻尼特性,被廣泛地應(yīng)用在航空航天、生物醫(yī)學(xué)工程、土木工程等領(lǐng)域。NiTi形狀記憶合金作為結(jié)構(gòu)中的關(guān)鍵元件,在服役過程中常常受到循環(huán)熱-力荷載的作用。在NiTi形狀記憶合金的循環(huán)變形過程中,功能性劣化(超彈性和形狀記憶效應(yīng)的劣化)和熱-力耦合效應(yīng)是兩個(gè)不可忽略的重要因素,并且相互作用和影響。因此,很有必要建立考慮功能性劣化特性和熱-力耦合效應(yīng)的本構(gòu)模型來描述和預(yù)測NiTi形狀記憶合金結(jié)構(gòu)和器件在各種復(fù)雜熱-力荷載作用下的循環(huán)變形特性。近年來,已有不少學(xué)者基于實(shí)驗(yàn)現(xiàn)象在不同尺度上建立了NiTi形狀記憶合金的本構(gòu)模型。在宏觀尺度上,已有的模型僅僅考慮了功能性劣化特性或熱-力耦合效應(yīng)中的一種,對(duì)功能性劣化特性的描述采用唯象方法,缺乏相應(yīng)的物理機(jī)理。在細(xì)觀尺度上,已有的模型僅僅關(guān)注NiTi形狀記憶合金在一個(gè)加-卸載下的熱-力學(xué)響應(yīng),由于尚未考慮到材料功能性劣化所對(duì)應(yīng)的內(nèi)在機(jī)制,無法對(duì)NiTi形狀記憶合金循環(huán)變形特性給出合理的描述�？梢�,已有的本構(gòu)模型還不夠完善,仍有較大的局限性。針對(duì)以上不足,本文將在不同尺度下建立NiTi形狀記憶合金的熱力耦合循環(huán)本構(gòu)模型,開展的創(chuàng)新性工作如下：(1)在宏觀尺度下,通過對(duì)已有宏觀-微觀實(shí)驗(yàn)現(xiàn)象的總結(jié),提出了NiTi形狀記憶合金在循環(huán)變形過程中超彈性劣化的物理機(jī)理,即馬氏體相變和缺陷的交互作用。基于熱力學(xué)框架,針對(duì)超彈性NiTi形狀記憶合金建立了一個(gè)能夠同時(shí)描述其超彈性劣化和率相關(guān)變形行為的熱-力耦合循環(huán)本構(gòu)模型。通過模擬和預(yù)測超彈性NiTi形狀記憶合金在不同加載率下的循環(huán)變形特性,驗(yàn)證了該模型的預(yù)測能力。進(jìn)一步,采用該模型預(yù)測了超彈性NiTi形狀記憶合金溫度相關(guān)的循環(huán)變形特性。(2)在單晶代表性體積單元上,通過確定的晶體學(xué)位向關(guān)系引入多種非彈性變形機(jī)制,即馬氏體相變、馬氏體重定向、馬氏體解孿、奧氏體塑性和馬氏體塑性,基于熱力學(xué)框架在單晶尺度下建立了熱-力耦合本構(gòu)模型。通過顯式過渡準(zhǔn)則和溫度均勻性假設(shè),將單晶模型過渡到了多晶。通過對(duì)多晶NiTi形狀記憶合金在不同溫度、不同加載率、不同應(yīng)力水平下的單軸和非比例多軸熱-力耦合變形特性的描述和預(yù)測,驗(yàn)證了模型的合理性和全面性。(3)通過總結(jié)已有的宏觀-微觀實(shí)驗(yàn)觀察,提出了一種新的非彈性變形機(jī)制,即馬氏體重定向誘發(fā)塑性。在工作(2)建立的晶體塑性模型基礎(chǔ)上,進(jìn)一步在單晶代表性體積單元上定量引入和NiTi形狀記憶合金功能性劣化相關(guān)的非彈性變形機(jī)制,即相變誘發(fā)塑性、重定向誘發(fā)塑性和殘余馬氏體的累積,進(jìn)而基于熱力學(xué)框架在單晶尺度下建立了熱-力耦合本構(gòu)模型。通過顯式過渡準(zhǔn)則和溫度均勻性假設(shè),將單晶模型過渡到多晶。通過對(duì)多晶NiTi形狀記憶合金在不同溫度下的單軸、非比例多軸以及率相關(guān)循環(huán)變形行為進(jìn)行了模擬和預(yù)測,驗(yàn)證了模型的預(yù)測能力。(4)在單晶代表性體積單元上,考慮馬氏體相變和相變誘發(fā)塑性兩種非彈性變形機(jī)制。將24個(gè)馬氏體處理成形態(tài)相同、但晶體學(xué)位向不同的橢球形夾雜鑲嵌在彈性各向異性的奧氏體基體中,并進(jìn)一步采用Mori-Tanaka均勻化方法得到奧氏體和每個(gè)馬氏體變體中的平均應(yīng)力場。基于馬氏體瞬間擴(kuò)展假設(shè),提出相變誘發(fā)塑性應(yīng)變及位錯(cuò)密度的正向、逆向繼承概念,在熱力學(xué)框架下建立了單晶細(xì)觀循環(huán)本構(gòu)模型。通過對(duì)單晶各向異性循環(huán)變形特性的描述和預(yù)測,驗(yàn)證了模型的正確性。
[Abstract]:NiTi shape memory alloy with excellent superelasticity and shape memory properties, biocompatibility and high damping properties, is widely used in aerospace, biomedical engineering, civil engineering and other fields of.NiTi shape memory alloy as a key element in the structure, are often served in cyclic thermo mechanical loads in the process. In the NiTi shape memory alloy during cyclic deformation, functional deterioration (degradation of super elasticity and shape memory effect) effect of coupling and thermal stress are two important factors that can not be ignored, and the interaction and influence. Therefore, it is necessary to consider the establishment of functional coupling effect and thermal degradation characteristics mechanical constitutive model to describe and predict NiTi shape memory alloy structures and devices in various complex thermo mechanical load under cyclic deformation characteristics. In recent years, many scholars have been based on experimental phenomena in different scales On establishing the constitutive model of NiTi shape memory alloy. On the macroscopic scale, the model only considers the coupling effect of a functional deterioration or thermal stress of the functional deterioration is described by phenomenological method, the lack of corresponding physical mechanism in meso scale. The existing models, focus only on NiTi shape memory alloy in a loading unloading under thermo mechanical response, due to the inherent mechanism of the corresponding functional material deterioration has not yet, not for NiTi shape memory alloy cyclic deformation characteristics is given a reasonable description. Thus, some have constitutive model is still not perfect, still there are many limitations. In view of the above shortcomings, this paper will establish a thermodynamic coupling of NiTi shape memory alloy under different scale cyclic constitutive model, innovative work carried out as follows: (1) at the macro scale, through the macroscopic and microscopic experiment In summary, NiTi shape memory alloy on the physical mechanism of super elastic cyclic deformation deterioration is proposed, namely the martensitic transformation and defect interaction. Based on the thermodynamic framework for superelasticity of NiTi shape memory alloy can also set up a description of its super elastic deterioration and rate dependent deformation behavior of thermal stress the coupled constitutive model. Through the simulation and prediction of superelastic NiTi shape memory alloy under different loading rate under cyclic deformation characteristics, verify the prediction ability of the model. Further, the prediction model of superelastic NiTi shape memory alloy temperature cyclic deformation characteristics. (2) in a single representative volume element on the introduction of a variety of non elastic deformation mechanism to determine the degree of the relationship between the crystal and the martensitic transformation, martensite reorientation, Martensite Twin solution plastic and martensite austenite, plastic, based on thermodynamic Study in the framework of the single crystal scale established under thermal stress coupling constitutive model. The explicit transition criterion and the temperature uniformity assumption, crystal transition to the polycrystalline model. The polycrystalline NiTi shape memory alloy at different temperature and different loading rate, different description and prediction of properties under uniaxial stress and the non proportional multiaxial thermal stress coupling deformation, verify that the model is reasonable and comprehensive. (3) by summarizing the macroscopic and microscopic observation, we propose a new non elastic deformation mechanism, namely Markov reorientation induced plasticity in the work. (2) the establishment of crystal plasticity on the basis of the model, further in a single representative volume element on the introduction of quantitative and NiTi shape memory alloy functional deterioration of non elastic deformation mechanism, namely the transformation induced plasticity, redirect induced plasticity and residual martensite accumulation, and thermal mechanical framework based on Single crystal scale was established under the thermal stress coupling constitutive model. The explicit transition criterion and the temperature uniformity assumption, single crystal model transition to polycrystalline. Based on polycrystalline NiTi shape memory alloy at different temperatures under uniaxial and multiaxial cyclic deformation behavior and the rate was simulated and predicted to verify the prediction ability of the model. (4) in a single representative volume element, the martensitic transformation and transformation induced plastic deformation mechanism of two kinds of non elastic. 24 martensite into the same shape, but the crystal degree to ellipsoidal inclusions embedded in the austenite matrix of elastic anisotropy in different, and further using Mori-Tanaka homogenization method to get the average stress of austenite and martensite in each field. Based on the assumption of instantaneous expansion of martensitic transformation induced plasticity, put forward strain and dislocation density, reverse the concept of inheritance, A single crystal mesoscopic cyclic constitutive model is established under the framework of thermodynamics. The correctness of the model is verified by describing and predicting the anisotropic cyclic deformation characteristics of single crystal.

【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG139.6
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本文編號(hào)：1448653