温度及粘弹性对介电弹性材料静动态力电耦合性能的影响研究

发布时间：2018-03-19 07:05

本文选题：介电弹性材料　切入点：温度　出处：《西安交通大学》2017年博士论文　论文类型：学位论文

【摘要】：介电弹性材料(Dielectric elastomer,DE)是制造柔性智能致动器最有潜力的电活性聚合物(Electroactive polymer,EAP)材料之一,可在电压驱动下产生大幅度的厚度与面积变形,最大面积应变高达1600%。针对现有研究对DE材料中的非线性力电耦合性能的研究尚不够充分,特别是温度和粘弹性影响及其动态特性研究缺乏,导致实际应用中对于材料的失效规律难以掌握及控制的问题,限制了其在工程中的推广和使用问题,本文以最典型的DE材料—VHB 4910为研究对象,深入研究温度及粘弹性对DE材料的静态和动态力电耦合性能的影响。论文首先通过实验研究了DE材料的基本力电特性,包括DE材料的力学性能,温度和频率对DE材料介电常数的影响,DE材料的玻璃化转变温度及热稳定性能等;基于实验结果分析了该材料的力电耦合性能,包括反映力电耦合特性的应变系数、电效率、机械效率和力电耦合效率。结果表明:依赖于频率和温度的弹性模量是影响该介电弹性材料致动变形的主要因素,而材料的介电常数对其致动性能的影响相对较小;DE的力电耦合效率随着频率的增大而减小,随着电场强度的增大和温度的升高变大。然后,论文从热力学的基本理论出发,建立了一种考虑温度因素的DE材料自由能平衡方程,分析了温度对DE材料的电击穿、力电失稳、张力损失、强度破坏等失效模式的影响,并给出了材料的稳定性工作区域,为DE材料的工程应用提供了相应的准则。在此基础上研究了温度和大变形引起的电致伸缩效应对DE稳定性的影响。结果发现,升高温度可以增大DE材料的变形,降低温度有利于提高DE材料发生力电失稳的临界电场强度,提高DE材料的稳定性;温度和大变形引起的电致伸缩应力可以抵消一部分Maxwell应力的压薄效应,一定条件下可以消除力电耦合失稳;实验结果验证了理论分析的有效性。随后,借助粘弹性的流变模型,将松弛粘弹性引入到DE材料的自由能模型中,研究了电压波形对考虑粘弹性后DE材料变形的影响,也研究了温度对考虑粘弹性后DE材料变形的影响。研究表明:粘弹性对DE材料的电致动变形影响很大,表现出非常明显的时间依赖性;恒定电压下,DE材料可以在较低的驱动电压和较长的工作时间下获得较大的致动变形,也可以在较高的驱动电压和较短的工作时间下获得较大的致动变形;斜坡电压下,电压上升的速率越小,变形越大,临界电压越小;温度越高DE材料的变形越大。论文通过实验研究了DE材料的粘弹性性能,证明了粘弹性对DE材料致动变形的影响规律。接着,通过欧拉-拉格朗日方程,建立了DE致动器的动力学方程,引入DE材料的松弛粘弹性力学模型,分别研究了温度和电压频率对考虑粘弹性后DE致动器的动力学性能的影响。结果表明:温度升高,系统的共振频率减小,振幅会增加;低频时,粘弹性松弛的影响非常明显,非弹性变形比较大,变形平衡位置出现蠕变上升的现象。最后,论文构建了DE致动器在力电耦合下动态变形的非线性动力学模型,详细分析了DE材料在动态载荷下的非线性动态变形规律,研究了DE致动器在交变载荷下的振动响应、相平面以及幅频响应,以及动态粘弹性阻尼的影响;通过庞加莱映射(Poincarémap)获得了DE致动器的动态稳定性演化过程。数值分析结果表明:预应力、电压和阻尼均影响着DE致动器的共振频率和动态响应。
[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.

【学位授予单位】：西安交通大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TB381

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