Aseismic performances of constrained damping lining structures made of rubber-sand-concrete

Flexible damping technology considering aseismic materials and aseismic structures seems be a good solution for engineering structures.In this study,a constrained damping structure for underground tunnel lining,using a rubber-sand-concrete(RSC)as the aseismic material,is proposed.The aseismic performances of constrained damping structure were investigated by a series of hammer impact tests.The damping layer thickness and shape effects on the aseismic performance such as effective duration and acceleration amplitude of time-domain analysis,composite loss factor and damping ratio of the transfer function analysis,and total vibration level of octave spectrum analysis were discussed.The hammer impact tests revealed that the relationship between the aseismic performance and damping layer thickness was not linear,and that the hollow damping layer had a better aseismic performance than the flat damping layer one.The aseismic performances of constrained damping structure under different seismicity magnitudes and geological conditions were investigated.The effects of the peak ground acceleration(PGA)and tunnel overburden depth on the aseismic performances such as the maximum principal stress and equivalent plastic strain(PEEQ)were discussed.The numerical results show the constrained damping structure proposed in this paper has a good aseismic performance,with PGA in the range(0.2-1.2)g and tunnel overburden depth in the range of 0-300 m.

Active Vibration Control of Beam Using Electro-magnetic Constrained Layer Damping

This paper investigates vibration control of beam through electro-magnetic constrained layer damping （EMCLD） which consists of electromagnet layer, permanent magnet layer and viscoelastic damping layer. When the coil of the electromagnet is electrified with proper control strategy, the electromagnet can exert magnetic force opposite to the direction of structural deformation so that the structural vibration is attenuated. A mathematical model is developed based on the equivalent current method to calculate the electromagnetic control force produced by EMCLD. The governing equations of the system are obtained using Hamilton＇s Principle and then reduced with the assumed-mode method. A simulation on vibration control of a cantilever beam is conducted under the velocity proportional feedback to demonstrate the energy dissipation capability of EMCLD, and the beam system with the same parameter is experimented. The results of experiment and simulation are compared and the results show that the EMCLD is an effective means for suppressing modal vibration. The results also indicate that the beam system has better control performance for larger control current. The EMCLD method presented in this paper provides an applicable and efficient tool for the vibration control of structures.

Free vibration of circular cylindrical shell with constrained layer damping

Free vibration characteristics of circular cylindrical shell with passive constrained layer damping （PCLD）are presented. Wave propagation approach rather than finite element method, transfer matrix method, and Rayleigh-Ritz method is used to solve the problem of vibration of PCLD circular cylindrical shell under a simply supported boundary condition at two ends. The governing equations of motion for the orthotropic cylindrical shell with PCLD are derived on the base of Sanders＇ thin shell theory. Nu- merical results show that the present method is more effective in comparison with other methods. The effects of the thickness of viscoelastic core and constrained layer, the elastic modulus ratio of orthotropic constrained layer, the complex shear modulus of viscoelastic core on frequency parameter, and the loss factor are discussed.

Influence of active constrained layer damping on the coupled vibration response of functionally graded magneto-electro-elastic plates with skewed edges

This article makes the first attempt in assessing the influence of active constrained layer damping(ACLD)treatment towards precise control of frequency responses of functionally graded skew-magneto-electroelastic(FGSMEE)plates by employing finite element methods.The materials are functionally graded across the thickness of the plate in terms of modest power-law distributions.The principal equations of motion of FGSMEE are derived via Hamilton’s principle and solved using condensation technique.The effect of ACLD patches are modelled by following the complex modulus approach(CMA).Additionally,distinctive emphasis is laid to evaluate the influence of geometrical skewness on the attenuation capabilities of the plate.The accuracy of the current analysis is corroborated with comparison of previous researches of similar kind.Additionally,a complete parametric study is directed to understand the combined impacts of various factors like coupling fields,patch location,fiber orientation of piezoelectric patch in association with skew angle and power-law index.

VIBRATION CONTROL OF FLUID-FILLED PRISMATIC SHELL WITH ACTIVE CONSTRAINED LAYER DAMPING TREATMENTS

Active constrained layer damping （ACLD） combines the simplicity and reliability of passive damping with the light weight and high efficiency of active actuators to obtain high damping over a wide frequency band. A fluid-filled prismatic shell is set up to investigate the validity and efficiency of ACLD treatments in the case of fluid-structure interaction. By using state subspace identification method, modal parameters of the ACLD system are identified and a state space model is established subsequently for the design of active control laws. Experiments are conducted to the fluid-filled prismatic shell subjected to random and impulse excitation, respectively, For comparison, the shell model without fluid interaction is experimented as well. Experimental results have shown that the ACLD treatments can suppress vibration of the fluid-free and fluid-filled prismatic shell effectively. Under the same control gain, vibration attenuation is almost the same in both cases.

DYNAMIC CHARACTERISTICS OF A CANTILEVER BEAM WITH PARTIAL SELF-SENSING ACTIVE CONSTRAINED LAYER DAMPING TREATMENT

The equations of motion governing the vibration of a cantilever beam with partially treated self-sensing active constrained layer damping treatment(SACLD) are derived by application of the extended Hamilton principle. The assumed-modes method and closed loop velocity feedback control law are used to analyze and control the flexural vibration of the beam nle influences of the bonding layer and piezoelectric layer thickness, material properties, placements of the Diezoelectric patch and feedback control parameters on the actuation ability of the vibration suppression are investigated. Some design considerations for pure passive, pure active control, and self-sensing active constrained layer damping are discussed.

Acoustic radiation from the submerged circular cylindrical shell treated with active constrained layer damping

Based on the transfer matrix method of exploring the circular cylindrical shell treated with active constrained layer damping（i.e., ACLD）, combined with the analytical solution of the Helmholtz equation for a point source, a multi-point multipole virtual source simulation method is for the first time proposed for solving the acoustic radiation problem of a submerged ACLD shell. This approach, wherein some virtual point sources are assumed to be evenly distributed on the axial line of the cylindrical shell, and the sound pressure could be written in the form of the sum of the wave functions series with the undetermined coefficients, is demonstrated to be accurate to achieve the radiation acoustic pressure of the pulsating and oscillating spheres respectively. Meanwhile, this approach is proved to be accurate to obtain the radiation acoustic pressure for a stiffened cylindrical shell. Then, the chosen number of the virtual distributed point sources and truncated number of the wave functions series are discussed to achieve the approximate radiation acoustic pressure of an ACLD cylindrical shell. Applying this method, different radiation acoustic pressures of a submerged ACLD cylindrical shell with different boundary conditions, different thickness values of viscoelastic and piezoelectric layer, different feedback gains for the piezoelectric layer and coverage of ACLD are discussed in detail. Results show that a thicker thickness and larger velocity gain for the piezoelectric layer and larger coverage of the ACLD layer can obtain a better damping effect for the whole structure in general. Whereas, laying a thicker viscoelastic layer is not always a better treatment to achieve a better acoustic characteristic.

Finite Element Modeling of a Fluid Filled Cylindrical Shell with Active Constrained Layer Damping

On the basis of the piezoelectric theory, Mindlin plate theory, viscoelastic theory and ideal fluid equation, the finite element modeling of a fluid-filled cylindrical shell with active constrained layer damping (ACLD) was discussed. Energy methods and Lagrange’s equation were used to obtain dynamic equations of the cylindrical shell with ACLD treatments, which was modeled as well with the finite element method. The GHM (Golla-Hughes-McTavish) method was applied to model the frequency dependent damping of viscoelastic material. Ideal and incompressible fluid was considered to establish the dynamic equations of the fluid-filled cylindrical shell with ACLD treatments, Numerical results obtained from the finite element analysis were compared with those from an experiment. The comparison shows that the proposed modeling method is accurate and reliable.

MULTI-LAYER PIEZOELECTRIC ACTUATOR AND ITS APPLICATION IN CONTROLLABLE CONSTRAINED DAMPING TREATMENT

A kind of novel multi-layer piezoelectric actuator is proposed and integrated with controllable constrained damping treatment to perform hybrid vibration control. The governing equation of the system is derived based on the constitutive equations of elastic, viscoelastic and piezoelectric materials, which shows that the magnitude of control force exerted by multi-layer piezoelectric actuator is the quadratic function of the number of piezoelectric laminates used but in direct proportion to control voltage. This means that the multi-layer actuator can produce greater actuating force than that by piezoelectric laminate actuator with the same area under the identical control voltage. The optimal location placement of the multi-layer piezoelectric actuator is also discussed. As an example, the hybrid vibration control of a cantilever rectangular thin-plate is numerically simulated and carried out experimentally. The simulated and experimental results validate the power of multi-layer piezoelectric actuator and indicate that the present hybrid damping technique can effectively suppress the low frequency modal vibration of the experimental thin-plate structure.

敷设约束阻尼层的工字梁振动特性研究

本文提出了一种计算带约束阻尼层梁振动响应的方法。以工字梁为研究对象,开展了室内振动试验,测得了不同位置的振动响应。并基于有限元法同步建立了数值仿真模型,利用模态应变能法准确计算了结构的自振频率和模态损耗因子。基于上述结果,利用模态叠加法进行谐响应分析,得到了约束阻尼层工字梁的振动响应结果。将振动响应的实测值与仿真值进行对比,验证了模型的准确性。分析了设计参数(阻尼层厚度、约束层厚度)对构件自振频率、模态损耗因子及加速度总振级的影响。研究结果表明:各板件的振动响应有着相似的变化规律,腹板加速度总振级最大,底板次之,顶板最小;总体上阻尼层厚度对工字梁前5阶自振频率影响不大,而随着约束层厚度的增大,构件前5阶自振频率先减小后增大;增大阻尼层厚度和约束层厚度都能持续增大构件的模态损耗因子,进而有效降低加速度总振级,且对腹板的减振效果好于顶板和底板。

智能约束层阻尼结构动力学建模及振动主动控制研究

基于耗散坐标与GHM(Golla-Hughes-Mctavish)模型建立智能约束层阻尼悬臂梁结构的动力学模型,并研究智能约束层悬臂梁结构的振动主动控制。针对结构模型自由度过高问题,分别在物理空间和模态空间对结构模型进行联合降阶处理。先通过具体算例验证了该研究建模方法的正确性,然后比较研究了压电片和黏弹性层铺设位置对系统振动控制效果和控制成本的影响。最后验证了结构简化模型的普遍适用性。研究结果显示,在控制器反馈增益相同的条件下,压电片和黏弹性层的位置越靠近固定端,系统控制效果越好,控制成本越小。简化的模型对含有噪声的输入信号也有较好的控制效果。

贴敷约束阻尼层的螺栓连接板半解析动力学建模及减振分析

在太空环境中太阳翼帆板的振动难以抑制,因此太阳翼帆板的减振研究至关重要。利用双搭接螺栓连接板结构模拟太阳翼帆板的展开状态,研究了通过贴敷约束阻尼层对其进行振动抑制的方法。创建了贴敷“H型”约束阻尼层双搭接螺栓连接板结构的半解析动力学模型,包含:利用层间剪切变形原理,推导了约束阻尼层结构的应力应变关系,用复模量表征黏弹性层的阻尼特性;考虑螺栓的影响区域,提出用复面弹簧单元和修正质量模拟双搭接螺栓结合部的刚度、阻尼和质量特性;引入正交多项式作为位移容许函数,利用拉格朗日方程和Hamilton原理建立了局部贴敷“H型”约束阻尼层的螺栓连接薄板的动力学方程。进行了实例研究,通过组建的试验系统证明了所创建的复合结构半解析模型在求解固有特性及振动响应参数方面的合理性,同时试验及半解析模型计算结果均证明约束阻尼层对双搭接螺栓连接板具有减振效果。最后,基于所创建的半解析模型分析了贴敷面积及约束阻尼层厚度对双搭接螺栓连接板减振效果的影响。

基于传递函数方法的局部覆盖环状CLD圆柱壳动力学分析

采用传递函数方法对局部覆盖环状约束层阻尼(CLD)圆柱壳进行了动力学分析。基于Donnell薄壳简化,由Hamilton原理导出了局部覆盖CLD圆柱壳的运动方程和边界条件,通过Laplace变换并引入状态向量后,建立了系统的状态空间方程,利用传递函数方法求解方程得到了系统的固有频率、损耗因子和频响曲线。算例分析结果验证了该方法的有效性和精确性,且更适于处理黏弹性材料具有频变特性的问题。讨论了CLD覆盖率和黏弹层厚度对系统固有频率和损耗因子的影响,为局部覆盖CLD圆柱壳的优化设计奠定了基础。

部分覆盖PCLD圆柱壳振动分析的新矩阵方法

基于线弹性薄壳理论和线粘弹性理论,考虑被动约束层阻尼(PCLD)的剪切耗能以及层间的相互作用,首次导出了适用于最一般情况的环状覆盖PCLD圆柱层合壳在谐激励作用下的整合一阶常微分矩阵方程,它的12个状态变量具有明确的物理意义,而且由层合壳完整的位移量和内力量组成,应用范围很广。通过将该模型和齐次扩容精细积分法结合构建了一种高效率和高精度的半解析半数值方法,并与解析解结果进行了对比,验证了该方法的正确性和有效性,借此还分析了PCLD覆盖率和覆盖位置对频率响应函数的影响。

SCLD板模态控制模型及振动控制

为有效抑制薄板在外界激励下的低频振动,对机敏约束层阻尼(SCLD)结构进行了主动振动控制研究.首先,考虑了黏弹性材料随温度与频率变化的阻尼特性,结合GHM阻尼模型建立了耦合系统有限元动力学分析模型;其次,考虑到结构动力学模型自由度庞大,采用物理坐标下自由度动力缩聚和状态方程下复模态截断进行了两次降阶,并通过复模态空间向实模态空间转换,得到了低维实模态控制模型;最后,通过模态实验验证了理论模型,并基于低阶控制模型设计了振动控制器,证明了研究方法的正确性.研究结果表明,采用本文的组合降阶方法可以有效地对SCLD结构进行降阶,对模态控制模型主动控制取得了良好控制效果:在单位阶跃激励下,振动响应衰减时间从0.20 s缩短为0.08 s;在随机白噪声激励作用下,振动响应均方根值降低了39.65%.

二维复杂弹性空腔的边光滑有限元建模及分析

在弹性空腔结构上敷设被动约束层阻尼(passive constraint layer damping, PCLD)可达到减振降噪的效果,针对这类复杂结构建立了二维复合弹性空腔的边光滑有限元耦合动力学模型。其中,PCLD结构采用两节点四自由度的PCLD梁单元,声场采用边光滑有限元模型。以二维全敷设复合矩形空腔模型为数值算例,以精细网格下的有限元法结果作为参考解,对比研究了在相同背景网格下,边光滑有限元法和有限元法的频响结果,发现前者更接近参考解,说明同样的计算成本下,边光滑有限元法具有更高的精确性,特别是在中频计算中。最后,分析了PCLD结构对某汽车驾驶舱的降噪效果,以及黏弹层和约束层厚度参数的影响规律,发现黏弹层厚度增大,可一定程度上降低空腔噪声,而约束层厚度增大,并不能在整个频段得到很好的降噪效果。

CLD空腔模态和阻尼特性的建模和仿真分析

在梁的弯曲理论和一阶剪切变形理论,考虑粘弹层的剪切变形和偏心的影响,导出了CLD梁的动力学控制方程,并写成一阶常微分方程的形式。可采用精细积分法求出梁端点状态向量间的传递关系。然后,根据连接点处的位移连续性条件和平衡方程,求出了相互连接的梁的状态向量之间的转换关系。结合单层梁和CLD梁端点间的传递关系和连接点处的转换关系,由传递矩阵原理建立了CLD空腔的自由振动特征方程。通过与文献值和有限元仿真结果的比较,证明了方法的有效性,采用上述方法分析了CLD结构对空腔模态和阻尼特性的影响。

声学黑洞约束阻尼板半解析耦合建模与振动特性研究

声学黑洞(ABH)以其优异的性能在结构减振降噪、声波调控、能量回收等领域展示了极其广阔的应用前景。但声学黑洞边缘截断会导致非零反射系数的存在,从而弱化声学黑洞效应。为此,本文在声学黑洞结构中引入约束阻尼材料,在Rayleigh-Ritz法框架下,选择高斯函数作为基函数,根据声学黑洞板的形状确定高斯基函数的分布,避免质量矩阵和刚度矩阵的奇异化,建立了声学黑洞约束阻尼板的半解析分析模型。通过与有限元分析结果对比,验证了半解析建模方法的正确性。研究了约束阻尼结构参数对声学黑洞板弯曲振动特性的影响规律,揭示了约束阻尼的减振机理和能量耗散作用。实验进一步验证了声学黑洞约束阻尼板的减振效果。

基于传递矩阵法分析ACLD圆柱壳振动控制问题的一种完全力电耦合模型

目前在ACLD薄壳结构的动力学分析中,通常采用一种忽略压电约束层面内电场强度,仅考虑在厚度方向为常量分布的法向电场强度的简化力电耦合模型。首先从理论上分析了简化力电耦合模型的局限性,进而提出了一种新的完全力电耦合模型,以此为基础导出了该模型下ACLD圆柱壳的一阶常微分矩阵状态方程,并结合传递矩阵法和齐次扩容精细积分法求解该方程。相对于传统三维模型方法,所建立的新模型和求解方法不仅大幅度简化了计算,而且适用于分析部分覆盖和任意支承条件下ACLD圆柱壳的振动控制问题。最后通过数值算例对完全力电耦合模型和简化力电耦合模型进行了比较,结果表明:简化力电耦合模型仅适用于低频分析;完全力电耦合模型具有更宽的频率适应性。