本文選題：介電彈性材料　切入點：溫度　出處：《西安交通大學(xué)》2017年博士論文　論文類型：學(xué)位論文

【摘要】：介電彈性材料(Dielectric elastomer,DE)是制造柔性智能致動器最有潛力的電活性聚合物(Electroactive polymer,EAP)材料之一,可在電壓驅(qū)動下產(chǎn)生大幅度的厚度與面積變形,最大面積應(yīng)變高達(dá)1600%。針對現(xiàn)有研究對DE材料中的非線性力電耦合性能的研究尚不夠充分,特別是溫度和粘彈性影響及其動態(tài)特性研究缺乏,導(dǎo)致實際應(yīng)用中對于材料的失效規(guī)律難以掌握及控制的問題,限制了其在工程中的推廣和使用問題,本文以最典型的DE材料—VHB 4910為研究對象,深入研究溫度及粘彈性對DE材料的靜態(tài)和動態(tài)力電耦合性能的影響。論文首先通過實驗研究了DE材料的基本力電特性,包括DE材料的力學(xué)性能,溫度和頻率對DE材料介電常數(shù)的影響,DE材料的玻璃化轉(zhuǎn)變溫度及熱穩(wěn)定性能等;基于實驗結(jié)果分析了該材料的力電耦合性能,包括反映力電耦合特性的應(yīng)變系數(shù)、電效率、機械效率和力電耦合效率。結(jié)果表明:依賴于頻率和溫度的彈性模量是影響該介電彈性材料致動變形的主要因素,而材料的介電常數(shù)對其致動性能的影響相對較小;DE的力電耦合效率隨著頻率的增大而減小,隨著電場強度的增大和溫度的升高變大。然后,論文從熱力學(xué)的基本理論出發(fā),建立了一種考慮溫度因素的DE材料自由能平衡方程,分析了溫度對DE材料的電擊穿、力電失穩(wěn)、張力損失、強度破壞等失效模式的影響,并給出了材料的穩(wěn)定性工作區(qū)域,為DE材料的工程應(yīng)用提供了相應(yīng)的準(zhǔn)則。在此基礎(chǔ)上研究了溫度和大變形引起的電致伸縮效應(yīng)對DE穩(wěn)定性的影響。結(jié)果發(fā)現(xiàn),升高溫度可以增大DE材料的變形,降低溫度有利于提高DE材料發(fā)生力電失穩(wěn)的臨界電場強度,提高DE材料的穩(wěn)定性;溫度和大變形引起的電致伸縮應(yīng)力可以抵消一部分Maxwell應(yīng)力的壓薄效應(yīng),一定條件下可以消除力電耦合失穩(wěn);實驗結(jié)果驗證了理論分析的有效性。隨后,借助粘彈性的流變模型,將松弛粘彈性引入到DE材料的自由能模型中,研究了電壓波形對考慮粘彈性后DE材料變形的影響,也研究了溫度對考慮粘彈性后DE材料變形的影響。研究表明:粘彈性對DE材料的電致動變形影響很大,表現(xiàn)出非常明顯的時間依賴性;恒定電壓下,DE材料可以在較低的驅(qū)動電壓和較長的工作時間下獲得較大的致動變形,也可以在較高的驅(qū)動電壓和較短的工作時間下獲得較大的致動變形;斜坡電壓下,電壓上升的速率越小,變形越大,臨界電壓越小;溫度越高DE材料的變形越大。論文通過實驗研究了DE材料的粘彈性性能,證明了粘彈性對DE材料致動變形的影響規(guī)律。接著,通過歐拉-拉格朗日方程,建立了DE致動器的動力學(xué)方程,引入DE材料的松弛粘彈性力學(xué)模型,分別研究了溫度和電壓頻率對考慮粘彈性后DE致動器的動力學(xué)性能的影響。結(jié)果表明:溫度升高,系統(tǒng)的共振頻率減小,振幅會增加;低頻時,粘彈性松弛的影響非常明顯,非彈性變形比較大,變形平衡位置出現(xiàn)蠕變上升的現(xiàn)象。最后,論文構(gòu)建了DE致動器在力電耦合下動態(tài)變形的非線性動力學(xué)模型,詳細(xì)分析了DE材料在動態(tài)載荷下的非線性動態(tài)變形規(guī)律,研究了DE致動器在交變載荷下的振動響應(yīng)、相平面以及幅頻響應(yīng),以及動態(tài)粘彈性阻尼的影響;通過龐加萊映射(Poincarémap)獲得了DE致動器的動態(tài)穩(wěn)定性演化過程。數(shù)值分析結(jié)果表明:預(yù)應(yīng)力、電壓和阻尼均影響著DE致動器的共振頻率和動態(tài)響應(yīng)。
[Abstract]:Dielectric elastomer (Dielectric elastomer DE) is an electroactive polymer manufacturing flexible smart actuators most potential (Electroactive polymer EAP) is one of the material, thickness and area can produce substantial deformation in driving voltage. The maximum strain area up to 1600%. according to the existing research on DE material nonlinear force electric coupling the performance is not enough, especially the temperature and viscoelastic effect on dynamic characteristics and deficiency, leads to the actual application for failure of materials is difficult to grasp and control, limit its promotion and use in engineering problems, this paper takes DE VHB 4910 as the object of study materials, the most typical, deep influence study on temperature and viscoelastic material of DE's static and dynamic performance of electromechanical coupling. Firstly, through the experimental study of DE material basic mechanical properties including mechanical and electrical properties of DE materials Can, effect of temperature and frequency on DE dielectric constant of the material, the glass transition temperature of DE materials and thermal stability; the experimental results analysis of electromechanical coupling properties of the materials based on the strain coefficient, reflect the mechanical characteristic of electric power efficiency, mechanical efficiency and power coupling efficiency. The results showed that: the elastic modulus is dependent on the frequency and temperature are the main factors that influence the dielectric elastomer actuator deformation, the influence of the dielectric constant of the actuating performance is relatively small; the power coupling efficiency of DE decreases with the increase of frequency, with the increase of electric field strength and temperature and then becomes larger. This paper, from the basic theory of thermodynamics, a kind of DE material free considering temperature can balance equation, analysis of shock temperature on DE material wear, mechanical and electrical instability, loss of tension, impact strength failure mode, And gives the stability regions of the material, provides the corresponding criterion for the engineering application of DE material. On the basis of temperature and deformation caused by the electrostrictive effect on the stability of DE. The results showed that the deformation temperature can increase the DE material, lowering the temperature is conducive to the improvement of DE mechanical and electrical materials critical electric field strength stability, improve the stability of DE material; caused by temperature and large deformation of electrostrictive stress pressure thin effect offset part of the Maxwell stress can, under certain conditions can eliminate force electric coupling instability; the experimental results verify the validity of theoretical analysis. Then, with the help of viscoelastic rheological model the elastic, viscoelastic relaxation will be introduced to the DE material free energy model, the voltage waveforms of the DE effect of the viscoelastic material deformation after the study, also studied the temperature on DE material deformation after considering the viscoelasticity Effect. The study shows that the viscoelastic material of DE electro dynamic deformation influence, showed very significant time dependence; constant voltage, the DE material can obtain larger actuation deformation in driving voltage and longer working time is lower, also can be in high voltage and short drive the working time under larger actuation deformation; ramp voltage, the voltage rise rate is smaller, the greater the deformation, the critical voltage is smaller; the higher deformation temperature of DE material increases. The viscoelastic properties of DE materials are studied through experiments, proves that the influence caused by the viscoelastic dynamic deformation of DE material. Then, the Euler Lagrange equation, the dynamics equation was established DE actuator, relaxation viscoelastic model is introduced into the DE material, the effect of temperature and voltage frequency on the viscoelastic dynamic DE actuator performance were studied The results show that with the increase of temperature. The resonance frequency of the system is reduced, the amplitude will increase; when the frequency is low, the effects of viscoelastic relaxation is very obvious, inelastic deformation is relatively large, the equilibrium position of the creep deformation rising phenomenon. Finally, the paper constructs a nonlinear dynamics model of DE actuator in electromechanical coupling dynamic deformation, detailed analysis the deformation rule of nonlinear dynamic DE materials under dynamic loading, the vibration of the DE actuator under alternating load response, phase plane and amplitude frequency response, and the influence of dynamic viscoelastic damping; through the Poincare mapping (Poincar map) to obtain the evolution of dynamic stability of DE actuator. The numerical results show that the prestressed, voltage and damping affect DE actuator resonance frequency and dynamic response.

【學(xué)位授予單位】：西安交通大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：TB381

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本文編號：1633317