管状介电弹性体驱动器电致应变特性分析

介电弹性体是电场型电活性聚合物的一种,在直流电场作用下,有良好的电致应变特性,去掉外加电场,可迅速恢复到原始尺寸,通过控制电压的大小,可以精确控制变形。本文基于NeoHookean应变能模型,采用ABAQUS有限元软件,开展了材质为丙烯酸聚合物管状介电弹性体驱动器在机电载荷作用下的力学性能有限元模拟,另外,考虑机械预拉伸的影响,开展了管状介电弹性体驱动器机电耦合特性的有限元仿真分析,为管状介电弹性体驱动器的力电特性、变形失效、稳定性的进一步研究提供了一定的理论依据。     

频率对VHB4910介电弹性体材料介电性能的影响

介电弹性材料是一种新型的电活性聚合物,在电激励下能产生较大的机械变形,可被广泛的用作致动器和传感器.其中3M公司的VHB4910系列丙烯酸薄膜是研究最广泛的介电弹性材料,其关键的电学参数,特别是介电常数,将影响整体的机电耦合性能.然而到目前为止,人们对于VHB4910介电材料介电常数取值的认识尚不统一,特别是频率对介电...     

平面形状为圆环形的混凝土框架结构温度应力研究

对平面形状为圆环形的混凝土框架结构在季节温差作用下构件的温度应力进行了研究.从理论上分析了圆环形混凝土框架结构在温度作用下结构变形、梁板中径向应力、环向应力、柱中应力特点,并通过算例进行了计算验证.研究结果表明:圆环形混凝土框架结构裂缝控制的重点为梁板中的环向应力和柱中应力.梁板中环向应力大小与径向位移约束系数成正比,...     

新型智能材料:电活性聚合物的研究状况

电活性聚合物(electroactive polymer,EAP)是一种智能材料,具有特殊的电性能和机械性能。本文综述了不同类型电活性聚合物材料的国内外研究现状。按照作用机理的不同,电活性聚合物主要分为两大类:电子型和离子型。电子型EAP材料在直流电场作用下可产生诱导位移,但是需要较高的激励电场(>100V/μm);离子型EAP材料可以在较低电压下(1~2V)产生诱导弯曲位移,但是需要保持一定的湿润度,而且在直流电场激励下很难保持稳定的诱导位移。本文还介绍了电活性聚合物材料的应用领域和发展前景。由于其显著的电致伸缩响应,电活性聚合物被应用于驱动器和传感器,而且在仿生领域具有更广阔的应用。此外,透明度较高的EAP材料可被用于光学设备上。目前,电活性聚合物的应用还处于尝试阶段,但是,其独特的性能决定了这种材料具有不可估量的应用前景。     

大直径薄壁复杂转接轴工艺研究

转接轴是一个结构复杂的大直径薄壁工件,尺寸精度、形位公差要求极高。通过分析工件结构特点,制定了合理的工艺路线,在半精车后和精车前分别进行了稳定处理;派制精车内外型面夹具、加长刀杆、内止口测具;编制半精车、精车内外型面数控程序,选择合适刀具在数控车床上进行加工,有效控制工件大外圆及端面的加工变形;解决加工深长孔振刀让刀问题,保证外圆、内孔尺寸及技术条件要求。     

褶皱发展对平面张拉薄膜屈曲后动力特性的影响

剪切位移荷载作用下,平面张拉薄膜经历缺陷、临界褶皱和宏观褶皱3种状态。该文依次分别对处于3种状态的薄膜进行自振特性分析,并明确了3种状态的划分原则。计入平面张拉薄膜的微小抗弯刚度,采用ANSYS/LS-DYNA中显式-隐式连续求解的方法对屈曲后薄膜的动力特性进行分析。依据忽略面外变形的理想模型自振特性分析结果,把平面张拉薄膜的振型划分为贯通振型和间断振型,贯通振型又划分为纵向贯通振型和横向贯通振型。研究结果表明:薄膜处于缺陷状态时,面外变形对薄膜自振特性的影响可以完全忽略,受主应力分布的影响,低阶振型中纵向贯通振型更易于出现,纵向贯通振型的波峰或波谷数量随着频率阶数的递增而规律递增。临界褶皱状态,薄膜的各阶频率均随剪切位移的增加而出现大幅波动,面外变形对薄膜振型的影响逐渐增大,横向贯通振型消失,纵向贯通振型的递增规律逐渐破坏;宏观褶皱状态,薄膜的各阶频率趋于稳定,其主应力分布及振型受面外变形的影响显著。     

正交铺设复合材料对称层合圆板的大挠度弯曲

本文探讨了纤维增强复合材料正交对称铺设层合圆板的大挠度弯曲问题.挠曲函数选用一项轴对称项和两项非轴对称项.应力函数由求解应变协调方程确定,用伽辽金法求解.计算表明:非轴对称主要通过薄膜力起作用,它仅对单层圆板的挠度分布有明显影响,对其挠度最大值影响不大;而对正交铺设层合圆板的影响则更小.由此可推论:对层合圆板(包括环形板)只需正交铺设各层纤维走向,其变形已趋轴对称,不必增加±45°铺设,从而简化了制作工艺过程.      

圆环形截面压电纤维复合材料有效电弹性性能研究

研究含周期分布压电纤维的压电复合材料的有效电弹性性能。通过在材料代表性体积单元边界上施加位移和电势周期边界条件,利用有限元法求得了代表性体积单元内的电弹性场。由平均电弹性场和压电复合材料有效电弹性性能定义,预测了圆环形截面压电纤维复合材料的有效电弹性系数。通过算例,比较了相同压电材料体积分数下圆环形截面压电纤维复合材料与圆截面压电纤维复合材料有效电弹性性能的差异,讨论了圆环形截面压电纤维内部非压电填充物的力学性质对有效压电系数的影响。该文结论可为高灵敏度压电复合材料设计提供 参考。     

大直径薄壁件的加工工艺研究

加工大直径特种材料薄壁零件极易产生变形问题,本文研究了一种材料为4J32的低膨胀合金的大直径薄壁零件,分析了薄壁零件加工变形主要是由装夹引起,提出采用端面压紧加工内孔和弹性胀套装夹加工外圆,可以有效地保证该零件的加工精度。最后通过对几批零件的质量跟踪,验证了该方法可有效控制零件的椭圆变形。     

预拉伸电活性绝缘弹性薄膜的机电驱动特性实验及分析

电活性聚合物是一类接近动物皮肤的驱动材料,在微小型机电系统、仿生机器人、柔性装置、功能结构等方面具有很大的应用潜力。绝缘弹性薄膜是其中的一类,驱动特性为大应变、低应力、快响应和高效率。文中从绝缘弹性薄膜HN1110的单向拉伸实验获取的实验数据,回归出材料特性参数;然后在平面双向预拉伸后进行高压驱动试验,获得基本的机电驱动特性数据;最后利用Mooney-Rivlin,Yeoh和Ogden三种模型研究其机电响应特性,依据试验结果对三种模型在变形范围、预拉伸量和模型特性等方面进行了分析和评价。     

Recent mathematical resuits in the nonlinear theory of flat and curved elastic membranes of revolution

The present article reviews some recent developments in nonlinear elastic membrane theory with special emphasis on axisymmetric deformation of flat circular and annular membranes subjected to a vertical surface load and with prescribed radial stresses or radial displacements at the edges. The nonlinear Föppl membrane theory of small finite deflections as well as a simplified version of Reissner's finite-rotation theory is employed, assuming linear stress-strain relations. The main analytical techniques are reported which have been applied recently in order to determine the ranges of those boundary parameters for which solutions of the relevant nonlinear boundary value problems exist, and ranges of parameters for which the principal stresses are nonnegative everywhere. Concerning plane membranes, it is shown how the mathematical theory of existence and uniqueness was nearly completed in recent works in contrast to curved membranes where references can be given to rather few results.(Deceased)     

Electro-active nano-composite actuator based on fullerene-reinforced Nafion

An electro-active artificial muscle based on the fullerene-reinforced ionic polymer membrane was newly developed to overcome some of the drawbacks of traditional ionic polymer–metal composite actuators. Tensile strength and Young’s modulus more than doubled with addition of minute quantities of fullerenes. While the ion exchange capacity of the fullerene–Nafion membrane does not change appreciably, proton conductivity and water-uptake ratio that are the main factors for higher magnitude of actuation increased dramatically. The harmonic responses of the fullerene-reinforced ionic polymer actuators almost doubled and the frequency responses greatly improved in the low-frequency region. The straightening-back phenomenon of the fullerene-reinforced actuator was considerably reduced with the addition of fullerene nano-particles.     

Large deflection analysis of thermo-mechanical loaded annular FGM plates on nonlinear elastic foundation via DQM

The effects of three-parameter elastic foundations and thermo-mechanical loading on axisymmetric large deflection response of a simply supported annular FGM plate are investigated. An annular FGM plate, resting on a three-parameter elastic foundation under a transverse uniform loading and a transverse non-uniform temperature, is considered. The mechanical and thermal properties of the FGM plate are assumed to be graded in the thickness direction according to a simple power law distribution in terms of the volume fractions of the constituents. The mathematical modeling of the plate and the resulting nonlinear governing equations of equilibrium are derived based on the first-order shear deformation theory (FSDT) in conjunction with nonlinear von Karman assumptions. A polynomial-based differential quadrature method is used as a simple but powerful numerical technique to discretize the nonlinear governing equations and to implement the boundary conditions. Finally, the effects of certain parameters, such as nonlinear foundations stiffness, volume fraction index, and temperature, on the axisymmetric large deflection response of the FGM plate are obtained and discussed in detail.     

Nonlinear bending analysis of annular FGM plates using higher-order shear deformation plate theories

This paper addresses the axisymmetric nonlinear bending analysis of an annular functionally graded plate under mechanical loading based on FSDT and TSDT. Using nonlinear von-Karman theory, the discretized equations are solved using the dynamic relaxation (DR) method combined with the finite difference technique. The effects of the material constant n, boundary conditions, thickness-to-radius ratio and shear deformation are studied. The results show that although, the difference between TSDT and FSDT becomes greater with an increasing thickness-to-external radius ratio, the effects of different types of boundary conditions is also of great importance.     

Biomimetic electro-active polymer based on sulfonated poly (styrene-b-ethylene-co-butylene-b-styrene)

Based on the sulfonated poly (styrene-b-ethylene-co-butylene-b-styrene) ionic membrane, a novel electro-active polymer, which can be used as sensors and actuators, was developed through the electroless plating procedure. The surface and cross-sectional morphologies of the SSEBS actuator were disclosed by using scanning electron microscope and transmission electron microscopy. The electromechanical results of the SSEBS actuators show high-speed bending actuation under constant voltages and also give excellent harmonic responses under sinusoidal excitation. In the voltage-current test, the electrical current is almost synchronous with the applied voltages, while the mechanical displacement shows high phase shift from the voltage signals. The SSEBS-based ionic polymer-metal composite can be a promising smart material and may possibly be used to implement biomimetic motion.     

广义洛仑兹力的磁弹性效应

导出了广义洛仑兹力的具体表达式,建立了壳体的非线性轴对称磁弹性方程,并讨论了广义洛仑兹力对磁场和机械场共同作用下载流薄圆柱壳体的力学及电磁效应的影响．     

Geometrically nonlinear axisymmetric analysis of thick laminated annular plate using FSDT

This paper presents geometrically nonlinear, axisymmetric, static and transient, moderately large deflection response of a laminated, composite, moderately thick annular plate subjected to uniformly distributed ring loads. The layers are considered to be polar orthotropic. Rotational inertia is included but the inplane inertia is neglected. First-order shear deformation theory is used in terms of the deflection w, rotation ψ of the midplane and the stress function Φ. The governing equations are solved by the orthogonal point collocation method and Newmark-β scheme. The effect of the radius-to-thickness ratio of the plate on the deflection and stress response is studied for symmetrically and unsymmetrically laminated plates.     

土中浅埋层合扁球壳的非线性动力响应

本文建立了考虑横向剪切影响、纤维增强对称正交铺设层合扁球壳的非线性动力方程。应用一维波阻法分析了土与结构的相互作用,对冲击波作用下土中浅埋周边弹性支承层合扁球壳的非线性动力响应问题进行了探讨。数值计算中考虑了各种材料参数及横向剪切变形对动力响应的影响。      

Large deflections and large amplitude vibrations of axisymmetric circular plates

This paper is concerned with conventional and mixed finite element analysis of large deflection bending and free vibration of axisymmetric circular plates including shear deformation. Conventional and mixed finite element formulations are presented. Numerical results are included for isotropic as well as orthotropic, circular and annular plates under various edge conditions and loadings.     

磺酸化石墨烯掺杂的离子交换聚合物电致动器

合成了磺酸化石墨烯单分子膜, 并按不同质量分数浇注了约200 μm厚的石墨烯/全氟磺酸杂化膜, 全反射衰减红外光谱验证了全部合成和掺杂过程; 对影响杂化膜电致动性能的相关物理参数进行了测试。 利用化学还原沉积技术在杂化膜两侧嵌入Pt纳米颗粒, 制成石墨烯/全氟磺酸-金属复合材料, 并进行了扫描电子显微镜观测。引入低频正弦电信号, 得到聚合物电致动器, 利用力和位移传感器测试其电致动性能。结果表明: 石墨烯掺杂后, 离子交换膜的柔韧性、 离子交换能力、 含水量均得到了一定程度的提高。金属Pt纳米电极表面平整; 颗粒较精细、 均匀; 电极与基底膜结合紧密。杂化膜具有高度的电致形变性能; 相同条件下, 最大输出位移可增加2.38倍。