电流变弹性体夹层结构梁的动力学仿真研究

对电流变弹性体夹层悬臂梁在不同电场控制下的振动响应特性和可控性进行研究。将电流变弹性体等效为一种具有电控力学性能的粘弹性阻尼材料,基于Hamilton原理建立了三层电流变弹性体夹层梁的有限元动力学方程,仿真分析了其在不同外加电场控制下的振动特性。分析结果显示,随着外加电场强度的增加,电流变弹性体夹层梁的固有频率不断增大,振动幅值却不断减小。表明电流变弹性体夹层梁具有与电流变液夹层梁相似的可控振动响应特性,能在外加电场作用下实现对结构振动的实时控制。     

复合材料面板对筒型基座整体抑振机制影响规律研究

提出一种新型复合材料筒型基座结构形式，其面板采用夹芯结构设计；通过系统阻抗特性分析理论预测面板结构及材料参数对基座减振性能的影响规律；针对夹芯面板开展静/动力学特性试验；以振级落差为减振效果评价指标，通过激振试验研究了面板结构参数对基座抑振机制的影响规律。研究结果表明：在频段 ，夹芯面板刚度能有效控制基座减振性能，随着频率的增加，面板刚度抑振机制减弱，阻尼高频损耗抑振机制增强；夹芯面板芯材厚度的增加对基座高频抑振性能优于表层厚度增加；面板对基座减振耗能贡献高于环壁间阻尼芯材。     

几种典型复合材料板振动特性综合对比分析及设计规律研究

为探究复合材料可设计参量对板格振动特性的影响规律,以玻璃钢板为设计基准,针对碳/玻混杂、橡胶格栅夹层、浮力材料格栅夹层等3种典型复合材料板方案,开展了固有频率和振动加速度振级特性的仿真分析和模型试验研究。研究结果表明,等厚度的碳/玻混杂板和玻璃钢板质量相当,碳/玻混杂板具有较好的振动抑制特性;格栅夹层板振动特性主要受芯材性能影响,浮力材料格栅夹层板刚度质量比最大,对测试频段内(0～2 000 Hz)振动都有较好的抑制作用,而橡胶格栅板对更高频段(2 000 Hz)振动抑制效果较好,因此在芯材选择时应选用高阻尼、刚度与格栅想接近的材料;20 mm等厚度的碳/玻混杂板振动响应略低于浮力材料格栅夹层板。以上结论可为复合材料板结构应用选型提供依据。     

磁流变弹性体夹层梁的振动响应特性实验研究

摘 要：设计和制备了基于磁流变弹性体材料的夹层结构梁,对所制备的磁流变弹性体夹层梁的振动响应特性进行了实验测试和分析。实验结果显示,在外加磁场作用下,磁流变弹性体夹层梁的振动响应幅值和固有频率将发生改变,具有减幅和移频特性。表明磁流变弹性体材料在磁场控制下,能改变夹层梁的振动响应特性,可实现对柔性梁的实时振动控制。     

带集中质量智能加肋板振动的自适应模糊控制

带有附加集中质量的加肋板振动控制问题在许多工程中都有重要意义.文章通过基于相互作用的带有附加集中质量和智能加肋梁的正交各向异性单向连续板振动问题的仿真力学模型,对加肋梁采用了ER电流变智能复合材料夹层梁的结构形式,并通过对ER流体施加电场,改变加肋梁结构的刚度和阻尼,从而调整带有附加集中质量加肋连续板的动力响应特性,对这一类结构进行了智能主动控制问题的仿真实验.在仿真试验数据的基础上应用自适应神经-模糊推理控制的方法,分别对激振频率和附加集中质量安装点的位置发生变化时,对带有附加集中质量的这种智能结构的振动问题进行了智能控制方法的仿真研究.仿真结果表明,自适应神经-模糊推理控制的方法能有效地抑制该类结构的振动.     

《多点敷设支撑层的粘弹性约束阻尼梁振动分析》

针对夹层约束阻尼梁结构的减振特性进行深入研究,在其基础上扩展多处敷设增设支撑层的约束阻尼,建立了多点铺设增设支撑层约束阻尼梁的振动特性模型,利用粘弹性材料的Maxwell模型、假设模态法、有限元理论和力学原理,结合功能特性方程和Lagrange方程,导出了增设支撑层约束阻尼梁的振动位移响应方程。通过对敷设双支撑约束阻尼简支梁在支撑层厚度变化的参数研究,可以看到增设适当厚度的支撑层能够达到更好的减振效果。     

电流变液用于旋转运动柔性梁振动控制的实验研究

建立了用于旋转运动电流变夹层梁振动响应测试的实验系统.对电流变夹层梁在不同电场强度与旋转速度下的振动响应特性进行了实验研究.实验结果显示,旋转运动电流变夹层梁在外加电场的作用下,能快速抑制梁的残余振动,缩短振动衰减时间.表明在外加电场的控制下,电流变材料能有效抑制旋转运动柔性梁的振动.     

电流变液夹层梁的动力学分析

将电流变材料处理为粘弹性材料,采用了线性粘弹性理论,基于夹层梁动力学分析方法,利用广义Hamilton原理,推导了电流变层合梁的动力学方程。在此基础上,研究了具有简单的边界条件夹层梁的动力学特性,得出了在外加电场作用下,电流变层合梁模态频率和模态损耗因子都随着电场的增大而增大;电流变层合梁的低阶模态损耗因子变化趋势大于高阶模态损耗因子的变化趋势;在同样的电场(或电压)作用下,层合梁的低阶模态损耗因子大于高阶模态损耗因子。这些结论表明了电流变层合梁在外加电场作用下,对低频振动具有较好的振动抑振效果。     

压电分流阻尼控制精密机械结构振动的研究

采用负阻抗变换器解决了压电分流电路中大亨值线绕电感的内阻影响抑振效能的问题.对硬盘驱动器(HDD)的磁头驱动臂这种典型精密机械结构的振动响应进行了压电分流阻尼抑制实验,对比分析了电路构型和参数优化方法对抑制效果的影响,研究了在高频微振动情况下,结构振动响应幅值对压电分流电路的抑振效果的影响.实验结果表明,改进的压电分流阻尼技术能有效抑制HDD驱动臂及磁头的瞬态和稳态振动响应.     

振动波分离引起的能量耗散性能分析

通过在结构上附加阻尼弹簧支撑,利用非经典阻尼引起的模态复化效应使系统产生振动局部化现象,研究了简支梁结构在简谐位移激励作用下振动响应的抑制问题。采用波传播法描述结构的位移响应,利用阻尼弹簧支撑限制行进波分量向梁左侧区域的传播,从而实现了行波和驻波的空间分离和振动能量的定向传递。采用振动功率流方法分析了结构中的波形转换、能量储存和流动,确定了振动能量的流动方向。详细研究了阻尼弹簧支撑设计对梁结构振动能量的耗散作用,揭示了行波与驻波分离发生时刻振动能量的传递规律。通过典型算例,充分展示了利用阻尼弹簧支撑抑制结构振动响应的效果。探讨了激励频率、支撑刚度、位置和阻尼系数等参数对振动能量耗散性能的影响,比较了不同设计方案的抑振效果和能量耗散状况。     

Fabrication and mechanical testing of glass fiber entangled sandwich beams: A comparison with honeycomb and foam sandwich beams

The aim of this paper is the fabrication and mechanical testing of entangled sandwich beam specimens and the comparison of their results with standard sandwich specimens with honeycomb and foam as core materials. The entangled sandwich specimens have glass fiber cores and glass woven fabric as skin materials. The tested glass fiber entangled sandwich beams possess low compressive and shear modulus as compared to honeycomb and foam sandwich beams of the same specifications. Although the entangled sandwich beams are heavier than the honeycomb and foam sandwich beams, the vibration tests show that the entangled sandwich beams possess higher damping ratios and low vibratory levels as compared to honeycomb and foam sandwich beams, making them suitable for vibro-acoustic applications where structural strength is of secondary importance, e.g., internal paneling of a helicopter.     

Characterization and numerical evaluation of vibration on elastic–viscoelastic sandwich structures

The objective of this paper is to study the vibration characteristic for a sandwich beam with silica/polymer blend as principal material, and pure polymer matrix as surface laminate. It is anticipated that high stiffness and structure damping of viscoelastic layer can be obtained by taking advantage of fascinating network of densely packed between silica and polymer matrix. Spherical particles of size 12–235 nm at various filler fraction (10–50 wt.%) and three different polymer matrices, polyacrylate, polyimide and polypropylene, were selected as the matrix materials. The mechanical damping and stiffness of the sandwich cantilever beam are recorded by using a Dynamic Mechanical Thermal Analyzer (DMTA). The silica’s small particle size feature and strain difference between principal and surface layers could highly enhance the energy dissipation ability of the beam structure. A numerical model is then developed and validated for the vibration of a symmetric elastic–viscoelastic sandwich beam. Experimental results show that the structure deformation for these sandwich beams with contiguous and constraining layers are in reasonable agreement with the prediction of the model. Both higher resonant vibrations are well damped in accordance with the symmetric motion of the elastic layers and relative little motion of the constraining layer.     

基于拓扑优化的压电分流阻尼抑振实验研究

将结构拓扑优化引入压电分流振动抑制中,以压电元件的分布面积为设计变量,压电元件产生的电荷最大化为优化目标,对压电元件的拓扑进行了优化以获得最佳抑振效果。针对悬臂梁结构,得到了对不同的结构模态进行抑制时的压电元件最优拓扑构型。建立了带有压电分流阻尼系统的悬臂梁振动控制实验模型,将压电元件拓扑优化后的压电分流阻尼系统应用于悬臂梁多阶弯曲模态的振动响应抑制实验,并对比分析了带最优拓扑和非优拓扑压电元件的悬臂梁压电分流阻尼抑振效果。结果表明,对压电元件进行拓扑优化可以明显提高压电分流阻尼系统的抑振效果。     

高斯激励黏弹性夹层梁的非线性随机响应特性

黏弹性夹层梁的随机振动控制是一个重要的实际问题。基于性能可控黏弹性体的夹层梁具有无需改变结构设计的可优化性而倍受关注。虽然关于该可控黏弹性夹层梁的振动已有一定研究,但所用的动力学模型在几何或物理上是线性的,而对于较强激励情况则需要考虑非线性因素。首次考虑该黏弹性体的物理非线性,建立黏弹性夹层梁及其支承质量系统的非线性运动微分方程,并离散化为多模态耦合的非线性振动方程;对于平稳随机激励,运用统计线性化法推导等价拟线性系统,并计算系统的随机响应,得到黏弹性夹层梁非线性随机振动的均方位移,及等价的频响函数和功率谱,用以评价可控黏弹性夹层梁的响应抑制性能。     

BIIR/P70共混物为夹层的三明治梁阻尼行为的DMA表征

文中通过动态力学分析仪DMA来表征三明治约束阻尼梁结构损耗因子随各种因素的变化情况。该三明治梁的阻尼层由溴化丁基橡胶和石油树脂的共混物组成。测试结果表明,DMA可以有效反映三明治梁的阻尼行为随温度、频率、组成的变化情况。为了解释DMA的测试结果,建立了合理的理论模型。通过调整石油树脂的含量,可以在室温和宽频范围内获得一个高的结构损耗因子。     

Behaviour of glued fibre composite sandwich structure in flexure: Experiment and Fibre Model Analysis

The behaviour of glued composite sandwich beams in flexure was investigated with a view of using this material for structural and civil engineering applications. The building block of this glue-laminated beam is a new generation composite sandwich structure made up of glass fibre reinforced polymer skins and a high strength phenolic core material. A simplified Fibre Model Analysis (FMA) usually used to analyse a concrete beam section is adopted to theoretically describe the flexural behaviour of the innovative sandwich beam structure. The analysis included the flexural behaviour of the glued sandwich beams in the flatwise and the edgewise positions. The FMA accounted for the non-linear behaviour of the phenolic core in compression, the cracking of the core in tension and the linear elastic behaviour of the fibre composite skin. The results of the FMA showed a good agreement with the experimental data showing the efficiency and practical applications of the simplified FMA in analysing and designing sandwich structures with high strength core material.     

Vibration and damping characteristics of beams with active constrained layer treatments under parametric variations

Hybrid damping designs with active piezoelectric materials and passive viscoelastic materials (VEMs) combine the advantages of both active and passive constrained layer damping (ACLD/PCLD) treatments.Researchers have established the standards for the extent and placement of the PCLD treatment for common structures. However for ACLD treatment, such detailed studies are not available. This study is aimed to examine, the effect of parametric variation of active constrained layer on the vibration control of the beams treated with optimally placed active or passive constrained layer damping patches. Finite element model is developed to model the open-loop and close-loop dynamics of active/passive constrained layer damping treated beam. The placement strategies of ACLD patches are devised using the modal strain energy (MSE) approach. Extensive experimentation studies are conducted by making twenty one separate samples of ACLD/PCLD treated beams with variations in viscoelastic material layer thickness, ACLD/PCLD patch coverage and location of the patch. Effects of key parameters, such as control gain, viscoelastic material thickness, coverage and location variation of ACLD patch on the system loss factor have been investigated. The careful analysis of results from partially covered ACLD treated beam suggests that the maximum damping of the first mode can be achieved by attaching the ACLD patch only up to 50% coverage. It also reveals that with proper choice of the control voltage and thickness, the effective loss factor can be almost doubled. The present study suggests the potential use of parametric studies that establish some guide lines for the extent and placement of the ACLD patches on the cantilevered beam.     

Non-linear active control of FG beams in thermal environments subjected to blast loads with integrated FGP sensor/actuator layers

Non-linear active control of dynamic response of functionally graded (FG) beams with rectangular cross-section in thermal environments exposed to blast loadings is presented. Two FG piezoelectric layers are bonded to the beam surfaces to act as sensor and actuator. Non-linear equations of motion of the smart beam are derived based on the first-order shear deformation theory and the von Karman geometrical non-linearity. Constant velocity feedback algorithm is used to control the dynamic response of the FG beam actively through closed loop control. The generalized differential quadrature method together with the Newmark-beta scheme is utilized to solve the non-linear partial differential equations in spatial and time domains. The resulted non-linear algebraic equations are then solved using the modified Newton–Raphson method. A detailed analysis of the influence of the geometric non-linearity, material parameters and temperature field on the active vibration control of FG beams subjected to various impulsive loads is carried out.     

振动主动阻尼控制的理论原理及控制策略

本文应用模态控制理论,对主动阻尼控制的理论原理及控制策略问题进行了研究,并对主动阻尼控制技术中的压电阻尼技术进行了实验研究,结果表明,通过选取合适的压电材料和选择适当控制策略,可以有效地提高结构阻尼及实现振动控制目的.     

利用厚度剪切压电效应的自适应压电复合材料夹芯结构的研究

提出了利用厚度剪切压电效应的压电复合材料(PCM TS) 作为夹芯结构芯材的新型驱动方式, 分析了PCM TS 的驱动原理。针对含有1-3 型PCM TS 芯材的夹芯梁结构, 实验研究了PCM TS 在静电场作用下的驱动特性, 并利用PCM TS 芯材对夹芯梁的振动进行了主动控制实验。结果表明, 利用PCM TS 作为驱动元件, 夹芯梁获得了比较理想的变形量, 其振动也能得到较为有效的控制, 因此是一种很有应用前途的驱动方式。