介电薄膜作动器的粘弹性行为研究

发布时间：2018-08-22 18:33

【摘要】：与传统的金属等硬质材料相比,软质材料具有多物理场响应、变形大等特点,在外界刺激下能够产生变形或发生某种响应,因此软质材料越来越受到科研人员的广泛关注。而介电弹性体(Dielectric Elastomer)作为典型的软质材料,比其他的软质材料综合性能要好,它具有质量轻、柔性好、反应时间短、力电转化率高等特点,因此该材料可以用来制造和设计成各种换能器,如作动器、能量采集器、传感器等。介电弹性体换能器通常是由平的、薄的介电弹性体薄膜组成,在大的外荷载作用下薄膜容易发生失效破坏。目前很多研究主要涉及介电弹性体材料与时间无关的弹性行为。而大多数介电弹性体是橡胶类材料,它的非线性变形和力电转化能力会受到与时间相关的耗散过程即力电耗散的影响。因此对介电弹性体粘弹性的研究可以改善和提高换能器的力电行为和力电性能。本文的主要研究内容包括(1)基于耗散介电弹性体的非线性理论和非平衡热力学原理,对圆形介电弹性体薄膜作动器在力电耦合作用下的粘弹性力学行为进行了研究。圆形薄膜中心粘接一轻质的刚性圆盘,然后薄膜外边界固定到刚性圆环上。在力电载荷作用下,圆形薄膜发生面外轴对称大变形。选取Neo-Hookean模型和粘弹性模型结合,通过非平衡热力学理论并利用能量变分原理推导出描述大变形的控制方程,而薄膜的粘弹性行为是由一个包含两个平行单元的弹簧—黏壶的流变模型来描述的。运用打靶法求出控制方程的数值解,并用图像描绘出了文中相关物理量的变化和薄膜的变形规律。结果表明当薄膜只受到外力作用时,在同一时刻随着外力的增大,径向拉伸、竖向位移等物理量的值也增大;当力一定时,它们的值随时间的推移逐渐增大并最终趋于稳定。而薄膜在力电耦合作用下,当力一定时,在同一时刻随着电压的增大,径向拉伸、竖向位移等物理量的值也增大;当电压一定时,它们的值随时间的推移逐渐增大并最终趋于稳定。该研究有助于介电薄膜作动器力电性能的提高。(2)在上述结论的基础上又进一步研究了设计参数对圆形介电薄膜作动器粘弹性行为的影响,研究结果表明对薄膜进行预拉伸,径向拉伸、竖向位移、电场强度等物理量的值随时间的推移最后趋于稳定,并且除了圆盘的竖向位移随着预拉伸的增大而减小外,其他物理量的值都随着预拉伸的增大而增大。薄膜在力电耦合作用下,改变其内外径的比值,径向拉伸、竖向位移、电场强度等物理量的值随时间的推移最后趋于稳定,并且除了圆盘的竖向位移随着内外径比值的增大而增大外,其他物理量的值都随着内外径比值的增大而减小。对介电作动器材料选取和器件的优化设计有一定的帮助。
[Abstract]:Compared with traditional hard materials such as metal, soft materials have the characteristics of multi-physical field response and large deformation, which can produce deformation or some kind of response under external stimulation. Therefore, soft materials have been paid more and more attention by researchers. The dielectric elastomer (Dielectric Elastomer), as a typical soft material, has better comprehensive properties than other soft materials. It has the advantages of light weight, good flexibility, short reaction time and high conversion rate. Therefore, the material can be used to manufacture and design various transducers, such as actuators, energy collectors, sensors and so on. Dielectric elastomer transducers are usually composed of flat thin dielectric elastomer films which are prone to failure under large external loads. At present, many studies are mainly concerned with the time-independent elastic behavior of dielectric elastomer materials. Most dielectric elastomers are rubber materials, and their nonlinear deformation and electromechanical transformation ability are affected by the time-dependent dissipation process, I. e., the force and electricity dissipation. Therefore, the study of viscoelasticity of dielectric elastomer can improve the electromechanical behavior and mechanical properties of the transducer. The main contents of this paper are as follows: (1) based on the nonlinear theory of dissipative dielectric elastomer and the nonequilibrium thermodynamic principle, the viscoelastic behavior of circular dielectric elastomer film actuator under the action of electromechanical coupling is studied. A lightweight rigid disk is attached to the center of the circular film, and the outer boundary of the film is fixed to the rigid ring. Under the action of mechanical and electrical load, the circular thin film is subjected to a large deformation of axial symmetry outside the plane. The Neo-Hookean model and the viscoelastic model are selected. The governing equations for large deformation are derived by using the theory of nonequilibrium thermodynamics and the energy variational principle. The viscoelastic behavior of the film is described by the rheological model of a spring-pot with two parallel elements. The numerical solution of the governing equation is obtained by using the shooting method, and the variation of the relevant physical quantities and the deformation law of the film are described by using the image. The results show that when the film is only subjected to external force, at the same time, with the increase of external force, the values of radial stretching and vertical displacement also increase, and when the force is fixed, their values gradually increase with the passage of time and eventually tend to stabilize. When the force is constant, the values of the physical quantities such as radial stretching and vertical displacement also increase with the increase of voltage when the force is constant, and when the voltage is fixed, Their values increase over time and eventually tend to stabilize. This study is helpful to improve the mechanical and electrical properties of dielectric thin film actuators. (2) based on the above conclusions, the effects of design parameters on viscoelastic behavior of circular dielectric film actuators are further studied. The results show that the films are prestretched. The values of radial tension, vertical displacement, electric field intensity and so on tend to be stable with time, and the values of other physical quantities increase with the increase of pretension, except that the vertical displacement of disk decreases with the increase of pretension. Under the action of electromechanical coupling, the values of physical quantities such as radial stretching, vertical displacement, electric field intensity and so on, which change the ratio of internal and external diameter of the film, finally tend to stabilize with the passage of time. In addition, the vertical displacement of the disk increases with the increase of the ratio of inner and outer diameter, and the values of other physical quantities decrease with the increase of the ratio of inner and outer diameter. It is helpful to the material selection of dielectric actuator and the optimum design of the device.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.2

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