A new variable stiffness absorber based on magneto-rheological elastomer

A new adaptive variable stiffness absorber was proposed based on a smart material, magnetorheological elastomer (MRE), and its vibration control performance was investigated. Before developing the proposed absorber, the MREs were firstly fabricated by curing a mixture of 704 silicon rubber, carbonyl iron particles and a small amount of silicone oil under an external magnetic field. Then the mechanical properties of the fabricated MREs were measured. On the basis of the measured mechanical characteristics, the MRE absorber was developed and its working characteristics were also tested under various input currents and excited frequencies. Finally, the control responses of a two-degree-of-freedom dynamic system with a MRE absorber were presented under a chirp input and used to evaluate the effectiveness of the MRE absorber.

Magneto-rheological elastomer (MRE) based composite structures for micro-vibration control

Magneto-rheological elastomers （MILEs） are used to construct composite structures for micro-vibration control of equipment under stochastic support-motion excitations. The dynamic behavior of MREs as a smart viscoelastic material is characterized by a complex modulus dependent on vibration frequency and controllable by external magnetic fields. Frequency-domain solution methods for stochastic micro-vibration response analysis of the MRE-based structural systems are developed to derive the system frequency-response function matrices and the expressions of the velocity response spectrum. With these equations, the root-mean-square （RMS） velocity responses in terms of the one-third octave frequency band spectrum can be calculated. Further, the optimization problem of the complex moduli of the MRE cores is defined by minimizing the velocity response spectra and the RMS velocity responses through altering the applied magnetic fields. Simulation results illustrate the influences of MRE parameters on the RMS velocity responses and the high response reduction capacities of the MRE-based structures. In addition, the developed frequency-domain analysis methods are applicable to sandwich beam structures with arbitrary cores characterized by complex shear moduli under stochastic excitations described by power spectral density functions, and are valid for a wide frequency range.

Electromechanical phase transition of a dielectric elastomer tube under internal pressure of constant mass

The electromechanical phase transition for a dielectric elastomer （DE） tube has been demonstrated in recent experiments, where it is found that the unbulged phase gradually changed into bulged phase. Previous theoretical works only studied the transition process under pressure control condition, which is not consistent with the real experimental condition. This paper focuses on more complex features of the electromechanical phase transition under internal pressure of constant mass. We derive the equilibrium equations and the condition for coexistent states for a DE tube under an internal pressure, a voltage through the thickness and an axial force. We find that under mass control condition the voltage needed to maintain the phase transition increases as the process proceeds. We analyze the entire process of electromechanical phase transition and find that the evolution of configurations is also different from that for pressure control condition.

Vibration Behavior of a Sandwich Porous Elliptical Micro-Shell with a Magneto-Rheological Core Based on the Modified Couple Stress Theory

Recently,the use of porous materials has grown widely in many structures,such as beams,plates,and shells.The characteristics of porous materials change in the thickness direction by different functions.This study has investigated the free vibration analysis of a sandwich porous elliptical micro-shell with a magneto-rheological fluid(MRF)core for the first time.Initially,we examined the displacement of the middle layer’s macro-and micro-components,using Love’s shell theory.Next,we used the modified couple stress theory(MCST)to obtain the strain and symmetrical curvature tensors for the three layers.The Hamilton’s principle was implemented to derive the equations of motion.We also used the Galerkin’s method to solve the equations of motion,resulting in a system of equations in the form of a linear eigenvalue problem.By solving the governing equations,we obtained the various natural frequencies and loss factors of the elliptical micro-shell,and compared them with the results in earlier studies.Lastly,we investigated the effects of thickness,porosity distribution pattern,aspect ratio,length scale parameter,and magnetic field intensity on the natural frequency and loss factor of the micro-shell.The data accuracy was validated by comparing them with those of reputable previous articles.

防弹玻璃用热塑性聚氨酯弹性体(TPU)中间膜性能研究

热塑性聚氨酯弹性体(TPU)作为核心的中间膜材料,在生产过程中极易受加工温度和剪切速率影响,导致其光学、力学性能不稳定及厚度不均。因此,研究热塑性聚氨酯弹性体(TPU)的工艺参数和中间膜表面改性,对提高防弹玻璃的品质和成本控制意义重大。通过实验数据得出:制备中间膜最优的机头温度为180℃,螺杆转速为50rpm,通过硅烷偶联剂表面改性可提升其热稳定性。

A 3D multi-field element for simulating the electromechanical coupling behavior of dielectric elastomers

We propose a multi-field implicit finite element method for analyzing the electromechanical behavior of dielectric elastomers. This method is based on a four-field variational principle, which includes displacement and electric potential for the electromechanical coupling analysis, and additional independent fields to address the incompressible constraint of the hyperelastic material. Linearization of the variational form and finite element discretization are adopted for the numerical implementation. A general FEM program framework is devel- oped using C＋＋ based on the open-source finite element library deal.II to implement this proposed algorithm. Numerical examples demonstrate the accuracy, convergence properties, mesh-independence properties, and scalability of this method. We also use the method for eigenvalue analysis of a dielectric elastomer actuator subject to electromechanical loadings. Our finite element implementation is available as an online supplementary material.

Effect of stick-slip on magneto-rheological elastomer with a magnetic field

This study investigated the stick-slip characteristics of a magneto-rheological elastomer (MRE) against an aluminum plate.Herein,the MRE was manufactured,and a stick-slip tester was employed to evaluate the stick-slip performance of the MRE under different velocities and load conditions with and without a magnetic field.The fast Fourier transform (FFT) of the friction force of the stick-slip and the roughness of the aluminum plate surface were calculated to confirm the stick-slip phenomenon.After the tests,the wear surfaces were observed to evaluate the wear properties of the MRE regarding the stick-slip.Results showed that the stick-slip was smaller at lower velocity.At higher velocity,the reduction of the stick-slip under a magnetic field was more clearly observed.Moreover,the wear reduced with reduced stick-slip under a magnetic field.

介电高弹体的力−电耦合循环变形和疲劳失效行为研究

介电高弹体的力−电耦合循环变形和疲劳失效行为目前在相关功能器件的设计和寿命评估中得到了越来越多的关注.因此,为了促进软体机器人等领域的发展,文章对介电高弹体的力−电耦合循环变形和疲劳失效行为的实验和理论研究现状进行了较为全面地综述:首先,对介电高弹体VHBTM材料在单一力场和力−电耦合作用下的循环变形行为及其演化特征进行了评述,重点总结了该材料在循环载荷作用下表现出的循环软化、棘轮行为和疲劳失效行为及其力−电耦合效应;然后,对已有的、描述介电高弹体单一力场和力−电耦合变形行为的本构模型进行综述,评述了已有的超弹性、黏−超弹性和黏−超弹性−塑性本构模型对介电高弹体循环变形行为及其力−电耦合效应的描述能力;最后,对介电高弹体的力−电耦合失效行为研究现状进行了评述,特别关注了介电高弹体在力−电耦合大变形作用下的低周疲劳失效行为.基于已有研究现状的评述,文章还对相关领域的未来研究方向进行了展望,力求促进相关研究领域的发展.

硅烷偶联剂改性聚氨酯的研究

从原料和工艺两方面出发,对以γ-氨丙基三乙氧基硅烷(KH550)为基础的硅烷改性聚氨酯(SPU)进行了改善。原料方面,改性后的KH550由伯氨基转化为仲氨基,反应活性降低;工艺方面,将KH550加料顺序提前。试验结果表明:这两种方法均有利于降低SPU树脂的黏度和提高反应平稳性;较好解决了由于黏度上升太快引起的KH550自聚凝团问题。

交联聚烯烃热塑性弹性体的性能研究 I. Engage 8180 的结构性能

研究了聚烯烃热塑性弹性体 Ｐ Ｏ Ｅ（ Ｅｎｇａｇｅ ８１８０） 的静态力学性能和动态力学性能，探讨了炭黑用量和炭黑表面预处理对 Ｐ Ｏ Ｅ性能的影响。结果表明：交联和填充都将使 Ｐ Ｏ Ｅ 的结晶度减小；硅烷偶联剂 Ｖ Ｔ Ｐ Ｓ（ 乙烯基三叔丁基过氧化硅烷） 和 Ａ１５１（ 乙烯基三乙氧基硅烷） 能够有效增强炭黑与 Ｐ Ｏ Ｅ 间的界面作用，从而使胶料各项物理性能得到改善，特别是内部动态温升大幅度下降，接近 Ｓ Ｂ Ｒ 的水平。这种胶料具有优异的耐老化性能、较高的动态模量和回弹性以及优异的耐磨性能。

介电弹性材料的机电耦合性能研究

作为一种新型的电活性聚合物,介电弹性材料可被用作柔性致动器。其中材料的介电性能和机械性能是影响其机电耦合致动性能的关键因素。通过实验方法研究了一种典型的介电弹性材料VHB4910在不同温度和频率下的介电常数和弹性模量,基于实验结果分析了该材料的机电耦合性能。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,对致动性能的影响最大可达4个数量级,材料的介电常数对其致动性能的影响相对较小。

硅烷偶联剂对介电弹性体复合材料电-机转化敏感度的影响

利用硅烷偶联剂KH550、KH570对无机纳米TiO2粒子进行表面改性,经机械共混及压延成型方法制备出3种界面结构的TiO2/室温硫化硅橡胶(RTV)介电弹性体复合材料。利用FTIR及DSC研究TiO2纳米粒子的表面改性情况,并研究不同硅烷偶联剂对复合材料介电性能和力学性能的影响。结果表明:KH550改性TiO2掺杂的复合材料较纯TiO2或KH570改性掺杂的复合材料其功能性明显提高。采用KH550改性TiO2使得复合材料拥有更高的介电常数,更低的弹性模量,使电-机转化敏感度较未改性前提高了57.4%。

硅烷改性聚氨酯丙烯酸酯的合成研究

以氨基硅烷偶联剂为基础,对以异氰酸酯基为端基的聚氨酯丙烯酸酯预聚体进行再封端,合成一系列不同封端率的单组分湿固化聚氨酯丙烯酸酯树脂。测试结果表明:硅烷偶联剂成功接枝在聚氨酯丙烯酸酯预聚体上。产物的表干时间、粘接强度、耐热耐水性得到较大改善。

介电弹性体卷形换能器设计与参数优化

为研究介电弹性体(DE)换能器在纯剪切拉伸模式下的发电特性,利用弹簧制作了具有预拉伸特性的DE卷形换能器,并结合Neo-Hooken模型建立了DE卷形换能器在纯剪切拉伸模式下的机电耦合数学模型,运用Matlab/Simulink软件建立了DE卷形换能器的纯剪切发电仿真模型,对DE卷形换能器的发电特性及不同弹簧系数对其发电特性的影响进行了仿真。对DE卷形换能器进行了实验,并与仿真结果对比。仿真与实验结果表明,DE卷形换能器发电特性优于一般拉伸模式换能器;在相同的拉伸条件及初始电压下,在预拉伸限制范围内,弹簧弹性系数越大其发电特性越好。

弹性胶泥阻尼器的冲击实验研究及建模分析

通过实验与理论分析相互结合的方法,以纯硅油和不同体积比例的固体颗粒为介质的弹性胶泥阻尼器为研究对象,对各阻尼器分别进行不同高度下的冲击实验,分析在固液耦合作用下弹性胶泥阻尼器的冲击性能变化。并且在冲击实验的基础上建立阻尼器的动力学模型,通过数值方法辨识模型中方程的各参数并与实测数值进行对比。研究工作对含固体颗粒的弹性胶泥阻尼器的冲击实验分析与动力学建模以及该类阻尼器的工程应用有着理论指导意义。

基于Neo-Hooken的介电弹性体单轴拉伸发电特性研究

为研究介电弹性体发电机(DEG)在单轴拉伸下的发电特性,结合Neo-Hooken模型建立了DEG在单轴拉伸下的机电耦合数学模型,运用Matlab/Simulink软件建立了DEG的单轴发电仿真模型,对DEG的发电过程及拉伸力、拉伸率、初始电压与电势差之间的关系进行了仿真研究,通过搭建DEG发电测试试验台,进行了试验研究并与仿真结果进行对比。仿真和试验结果表明在单轴拉伸收缩发电过程中,DEG两端电压先降后升;在初始拉伸时和即将拉伸至最大时电压有两个突变点;电势差随着初始电压、拉伸力的增加而近似线性增加。

介电弹性体圆柱形驱动器机电耦合致动过程分析

驱动器薄膜施加高压直流电后产生的轴向力差能使圆柱形驱动器伸长。为研究介电弹性体圆柱形驱动器的动态反应,本文对其机电耦合致动原理及过程进行了分析。圆柱形驱动器的机电耦合致动过程类似于蠕变过程,提出一种广义Voigt线性粘弹性模型来对其进行描述,并对计算结果与试验之间产生误差的主要原因进行分析。根据驱动器机电耦合致动过程中驱动器的准静态位移的非线性及轴向应力的变化对原模型进行改进。试验表明,在驱动器工作电压范围内,改进的广义Voigt模型能较好地描述驱动器机电耦合致动过程,此模型可用于介电弹性体圆柱形驱动器的性能预测和优化。

基于介电弹性体的驱动器研究进展

针对目前介电弹性体驱动器成本高、能量转换效率低等问题,简要介绍了介电弹性体发电的基本原理及拉伸模式的研究进展,总结了国内外不同基于介电弹性体驱动器的构型研究进展,对不同类型的驱动器特点及适用场合进行了分析,并对它们的性能特征、加工技术和潜在应用等方面进行了讨论。最后阐述了当前介电弹性体驱动器研究方面亟待解决的问题,并对进一步解决上述问题提出了建议。

电场活化聚合物驱动器动态机电耦合特性研究

通过分析电场活化聚合物材料的力学行为理论,建立了基于常见应变能函数(Mooney-Rivlin模型、Ogden模型和Yeoh模型)的电场活化聚合物驱动器的机电耦合本构模型。通过驱动实验,将3种机电耦合模型结果与实验数据进行了对比分析,得出影响电场活化聚合物机电稳定性的重要因素,确定了最适用于电场活化聚合物的机电耦合性能行为的模型。

磁流变弹性体环形板的应力应变分析

通过运动方程、物理方程、几何方程及电动力学方程给出了磁流变弹性体薄板在机械场、磁场作用下的基本方程,以磁流变弹性体环形薄板问题为例,建立了含有8个基本未知量的偏微分方程组,再利用Newmark有限等差式,得到了可以应用离散正交法求解的标准型。对于变化磁场下的磁流变弹性体薄板,得到了磁场力的表达式。讨论了磁流变弹性体薄板应力、变形随外加磁场参量的变化规律,并通过实例证实了可以通过改变磁场、机械场的参数来实现对薄板的应力、应变的控制。