【作者】 雷鸣；

【导师】 王惠明；

【作者基本信息】 浙江大学 ， 固体力学， 2015， 硕士

【摘要】 与工程中广泛使用的硬材料相比,自然界中存在着许多柔性的结构,例如章鱼的脚、有触摸反应的含羞草等。人们一直致力于新型材料的研发,以模仿生命中的一些显著而优异的特征。介电高弹聚合物以其优越的变形特性逐渐进入人们的视野,它在外加电场下,可产生超过100%的应变。除此之外,它还有着响应快、噪声低、质轻价廉、疲劳寿命高以及仿生性能突出等优点,因此,越来越多地应用于各类智能驱动器诸如智能机器人、盲文显示器、光学透镜、能量收集器等方面,在人工肌肉、智能仿生、航空航天、机械等领域都有着巨大的应用潜力。研究发现,介电高弹聚合物器件在使用过程中与拉伸速率关系很大,不仅影响转换器使用效率,也会对器件输出、响应速度产生很大的影响,而这种拉伸速率相关的现象正是介电高弹聚合物材料粘弹性效应的结果。越来越多的研究表明,粘弹性作为介电高弹聚合物材料的一个显著特征不可被忽略,因此,关于介电高弹聚合物粘弹性的理论研究很有必要,这也是本文的主要研究工作。本文基于热力学框架与连续介质力学模型的介电高弹聚合物理论,耦合了大变形和力电加载,描述了介电高弹聚合物非线性、非平衡以及动力学行为。基于该模型,分别以介电高弹聚合物圆形薄膜和圆环形作动器为研究对象,研究不同载荷、电压或是参数改变情况下模型的粘弹性特性,以下是三个方面的主要工作：(1)考虑粘弹性作用的影响,通过引入弹簧-阻尼器模型推导出介电高弹聚合物的热力学控制方程,为介电高弹聚合物的粘弹性求解提供理论基础；(2)考虑受到电压和内部压力共同作用下,基于介电高弹聚合物圆形薄膜,分析得到考虑粘弹性效应下的介电高弹聚合物的物理场分布和演化规律,并很好地描述了此时材料的力电稳定性行为；(3)建立圆环形作动器考虑粘弹性松弛的力学模型,并讨论不同参数对器件力学行为的影响。通过模拟介电高弹聚合物粘弹性演化的规律,为器件的力电失稳行为预测、随时间相关的变形行为提供理论依据,对考虑粘弹性行为的介电高弹聚合物产品的优化设计等也具有实际的借鉴和指导意义。更多还原

【Abstract】 Compared with hard materials widely used in engineering, many flexible structures exist in nature, such as octopus legs, mimosa with touch reactions and so on. It has been an important target to develop new materials, to mimic the significant and excellent characteristics of the life. Dielectric elastomers gradually come into people’s perspective with their superior characteristics. For example, they can produce more than 100% strain under an external electric field. In addition to large voltage-induced strains, they have some other advantages such as fast response, low noise, light and cheap, high fatigue life and outstanding performance in bionics, therefore, they have been used more and more in many kinds of intelligent drives such as intelligent robots, Braille displays, optical lenses, energy harvester et al. They also have great potential applications in artificial muscles, intelligent bionic, aerospace, machinery and other fields.It is found that the dielectric elastomers are usually stretch-rate dependent, which not only affects the efficiency of converters, but also has a huge impact on the output and response speed of the devices. In fact, the stretch-rate dependent behaviors are usually interpreted as the consequence of the viscoelasticity of the polymers. More and more studies show that the viscoelasticity is a significant feature of dielectric elastomers and cannot be ignored. So the investigation on viscoelasticity of dielectric elastomer is necessary.This paper describes the nonlinear, non-equilibrium and dynamic behaviors of dielectric elastomers when coupled with large deformation and electro-mechanical load, based on the model of continuum mechanics and thermodynamics framework. Based on this model, we study the viscoelastic properties of round film and circular ring actuator under different mechanical loads and voltages. The main works are as following:(1) Considering the viscoelastic effects, we derived the thermodynamic equations by introducing the spring-damper model and provided a theoretical basis and solving method for the viscoelastic problem; (2) Considering the coupling effect of the mechanical and voltage, we obtained the distribution and evolution of the physical field based on the viscoelastic model and round film, and presented a good description of the electromechanical instability behavior of this model; (3) We established the analytical model of viscoelastic ring actuator, analyzed the mechanical behavior of the actuators, and studied the effect of different parameters on the output. We provided a theoretical basis for the prediction of electromechanical instability and the deformation behaviors when considering the viscoelastic effect. It also provides a practical reference or guidance for the product design optimization when the viscoelastic effect is considered.更多还原