约束阻尼板的主被动一体化振动控制

基于虚功原理,提出了一种新的建立主动约束阻尼板动力学模型的方法。该方法采用层合理论推导出约束阻尼板结构的动力方程,用GHM(Golla Hughes McTavish)方法引入辅助的耗散坐标,来描述粘弹性材料随频率变化的特性,并采用LQR方法控制结构的振动。其有效性通过算例进行了验证。同传统的有限元建模理论比较,采用层合理论,减少了结构自由度,并且具有良好的计算精度。     

粘弹性阻尼层叶片耗损特性分析研究

通过有限元软件建立2MW风力机复合材料叶片模型,通过固有频率和静强度分析验证模型合理性,并确定动态薄弱区域。对粘弹性阻尼层叶片进行谐响应分析,基于应变能变化率方法建立耗损特性模型,分析了粘弹性阻尼层的厚度、模量以及叶片损伤对结构耗损特性的影响。研究结果表明:粘弹性阻尼层厚度对叶片耗损特性有重要影响;粘弹性阻尼层对叶片损伤有一定的修复能力,能够抵抗叶片损伤、延长使用寿命。这将为粘弹性阻尼层叶片在工程应用中提供理论依据和支持。     

敷设支撑层的约束阻尼梁减振优化设计

约束阻尼是板梁减振降噪的重要手段之一,敷设支撑层的约束阻尼结构能够获得更好的减振效果.基于有限元方法建立简支约束阻尼梁模型,以阻尼段段数、长度、段间间隙、支撑层厚度作为设计变量,梁结构的前4阶模态损耗因子乘以权值的和为目标函数,应用序列二次规划法对整个结构进行优化.在不同质量的约束条件下,分析比较了选取不同权值时约束层连续与间断情况下梁中点的振幅变化和损耗因子的变化.实例结果表明:优化设计能够保证在引入质量较小的情况下,达到更好的减振效果.     

层间过渡约束阻尼梁有限元建模与振动-阻尼特性分析

三层约束阻尼结构常被用于工程结构的减振降噪设计中,为了增加其抗振性能,可在黏弹层和基层中间加入一层"过渡层",从而构成一种新的层间过渡约束阻尼结构。基于一阶剪切变形理论和哈密顿原理建立有限元模型,对该结构进行相应的振动和阻尼特性分析。为验证该模型正确性,与解析解进行对比,二者计算结果吻合良好。以悬臂阻尼梁为例,与传统的约束阻尼梁进行对比,计算结果表明增加"过渡层"可以增大结构的损耗因子,进而提高减振耗能效果。同时还讨论了过渡层的材料如何选择以及其参数对系统的固有频率和损耗因子的影响,为进一步的优化工作及实际工程应用提供了一定的参考。     

基于Hoff夹层板理论计算约束阻尼结构的结构损耗因子

利用Hoff夹层板理论研究约束阻尼结构的固有频率和模态损耗因子的计算问题.计算结果表明,利用Hoff理论计算约束阻尼结构固有频率和模态损耗因子方法具有较高的计算精度,与Ansys计算结果较为接近,可用于约束阻尼结构固有频率和结构损耗因子计算.     

被动约束层阻尼梁动力学优化研究

研究被动约束层阻尼(passive constrained layer damping,PCLD)梁的动力学优化问题,优化变量为PCLD的起始位置、覆盖长度、阻尼层厚度和约束层厚度。在局部覆盖PCLD梁动力学特性的传递函数解的基础上,建立PCLD梁的单目标和多目标优化模型。单目标优化中以结构模态损耗因子最大为优化目标,讨论约束条件中PCLD附加结构质量系数对优化结果的影响。多目标优化中以各阶模态损耗因子最大、各阶固有频率改变量最小和PCLD附加的结构质量最小为优化目标,增加约束层纵振频率的约束条件,讨论优化目标函数中各权重系数对优化结果的影响。此外,还在有限元软件MSC.Patran/Nastran中二次开发出PCLD梁动力学优化模块。两种方法的优化结果一致,验证本文计算结果的正确性。     

被动约束层阻尼梁的动力学建模和分析

基于弹性梁的弯曲振动理论,建立了基梁和约束层的控制方程。考虑粘性层的剪切变形,由线粘弹性理论求出层间的切向相互作用力。然后,结合基梁、约束层的控制方程和粘性层的法向平衡方程,消去层间的法向相互作用力,导出敷有被动约束层阻尼弹性梁的整合一阶常微分矩阵方程。利用精细积分法对控制方程进行求解,分析了结构的固有频率和损耗因子,与相关文献的比较验证了此方法的正确性。最后,分析了结构参数对被动约束阻尼梁的自由振动特性和阻尼特性的影响。     

被动约束层阻尼梁的动力学建模和分析北大核心

基于弹性梁的弯曲振动理论,建立了基梁和约束层的控制方程。考虑粘性层的剪切变形,由线粘弹性理论求出层间的切向相互作用力。然后,结合基梁、约束层的控制方程和粘性层的法向平衡方程,消去层间的法向相互作用力,导出敷有被动约束层阻尼弹性梁的整合一阶常微分矩阵方程。利用精细积分法对控制方程进行求解,分析了结构的固有频率和损耗因子,与相关文献的比较验证了此方法的正确性。最后,分析了结构参数对被动约束阻尼梁的自由振动特性和阻尼特性的影响。     

约束层阻尼板的有限元建模研究

粘弹性材料（VEM）的本构关系随频率和温度的变化而变化，对粘弹结构难以进行动特性分析及控制研究。基于Hamilton原理，给出了一种建立约束层阻尼（CLD）板动力学方程的新建模方法，建模时，考虑到VEM的纵向位移影响，并引入虚拟自由度，导出了标准二阶定常线性系统模型，从而避免因粘弹性材料导致的高阶非线性方程。采用GHM方法描述VEM的本构关系，它能直接与有限元法融合。算例分析了夹芯层为ZN—1型粘弹性材料的CLD悬臂板的动态特性，并与相关文献中的计算及试验结果进行比较，计算结果更加准确，表明新建模方法是准确的。     

A compressional-shear model for vibration control of beams with active constrained layer damping

In the modeling of the active constrained layer damping (ACLD) structures, the transverse displacements of the constraining layer and the host structures are usually assumed to be compatible. However, when performing active control, even a small difference between the transverse displacement of the constraining layer attached with actuator and that of the host structures bonded with sensor may destabilize the closed-loop control system. In order to understand the effect of incompatible transverse displacements, a model for the beam with ACLD in which both compressional vibration and shear damping are considered, is developed. In this model, the viscoelastic layer is modeled to carry not only the shear strain but also the peel strain. In addition, a thorough solution scheme to obtain the eigenvalues and frequency response of the closed-loop controlled beam is also given based on multiple shooting method. The effects of the compressional vibration on passive and active control are investigated through simulation examples. It is found that the compressional vibration can significantly affect the frequencies and damping ratios of higher-order modes of an actively controlled beam and may even destabilize the active control.     

Concrete-based constrained layer damping

This paper describes a novel structural damping method that allows a fabricated (welded) machine tool structure to be designed for minimum cost and maximum dynamic stiffness comparable to polymer concrete structures. The damping method is a constrained layer damping (CLD) design where the layers are replicated in place using expanding concrete inside of viscoelastic damping inserts. The novel design is highly flexible and economical while providing excellent damping for a wide range of structural shapes.     

Dynamic characteristics analysis of active constrained layer damping plate with various boundary conditions

Considering the direct and converse piezoelectric effect, expressions of piezoelectric membrane internal forces in the piezoelectric constrained layer were given. The control equations of the piezoelectric constrained layer and host plate were obtained in according with the thin plate theory. Based on the layer wised principle, the integrated first order differential equation of an active constrained layer damping (ACLD) plate was derived for the simply supported boundary condition. Then, this method was expanded to the ACLD plate with cantilever boundary condition by virtue of geometric analogy method. Employing the extended homogeneous capacity precision integration approach, a high precision semi-analytical method was proposed to analyze the dynamic characteristics of the ACLD plate with various boundary conditions. The comparison with the literature results has verified the accuracy and effectiveness of the present method.     

Vibrations of a cylindrical shell with partially constrained layer damping (CLD) treatment

This paper presents a mathematical model for a cylindrical shell with a partially constrained layer damping (CLD) treatment. A thin shell theory in conjunction with the Donnell–Mushtari–Vlasov assumptions is employed to yield the model. Employing the assumed-mode method, the discretized equations of motion in terms of shell’s transverse modal coordinates are derived. The effects of treatment length, of constraining layer (CL) thickness and stiffness, and of viscoelastic material core (VEM) thickness are then discussed. Numerical results show that thicker or stiffer CL warrants better damping. Thicker VEM does not always give better damping than thinner ones when CL exceeds a certain thickness.     

Modeling and analysis of rotating plates by using self-sensing active constrained layer damping

This paper proposes a new finite element model for active constrained layer damped (CLD) rotating plate with self-sensing technique. Constrained layer damping can effectively reduce the vibration in rotating structures. Unfortunately, most existing research models the rotating structures as beams that are not the case many times. It is meaningful to model the rotating part as plates because of improvements on both the accuracy and the versatility. At the same time, existing research shows that the active constrained layer damping provides a more effective vibration control approach than the passive constrained layer damping. Thus, in this work, a single layer finite element is adopted to model a three-layer active constrained layer damped rotating plate. Unlike previous ones, this finite element model treats all three layers as having the both shear and extension strains, so all types of damping are taken into account. Also, the constraining layer is made of piezoelectric material to work as both the self-sensing sensor and actuator. Then, a proportional control strategy is implemented to effectively control the displacement of the tip end of the rotating plate. Additionally, a parametric study is conducted to explore the impact of some design parameters on structure??s modal characteristics.     

The use of constrained layer damping in vibration control

Constrained layer damping is widely used in engineering practice for minimizing unwanted vibration. This paper describes an application to an outlet guide vane whereby damping treatments are considered in terms of external constrained layers and internal fillers. The problem of optimizing the characteristics of shear damping at room and elevated temperatures is shown to be a difficult problem.     

带阻尼套筒的篦齿封严结构模态计算方法研究

这里采用波传播技术对带阻尼套筒的篦齿封严结构进行了振动特性的计算分析,通过建立接触面刚度矩阵来模拟阻尼套筒对篦齿封严结构固有振动特性的影响,对各参数进行无量纲处理,使所得结论具有通用性效果。     

Exact dynamic analysis of composite beams with partial interaction

The partial differential equations and general solutions for the deflection and internal actions and the pertaining consistent boundary conditions are presented for composite Euler-Bernoulli members with interlayer slip subjected to general dynamic loading. Both free and forced vibrations are treated. The solutions are shown to be unique and complete under certain conditions, and valid for all so-called restricted admissible boundary conditions. Specifically, the exact eigenmode length coefficients are derived for the four Euler BC. They differ from those valid for ordinary, fully composite (solid) beams, except for the pinned-pinned case. The maximum deviation for beams with the other three Euler BC is shown to be less than 2-6% with respect to the eigenmode length coefficient and 3-10% with respect to the eigenfrequency, respectively, depending on the two non-dimensional parameters, composite action or shear connector stiffness and relative bending stiffness parameters. However, these deviations occur in a rather narrow range of the determining parameters, so for most practical cases the eigenmode length coefficients given for solid (fully composite) beams can approximately be used also for partially composite beams. The procedures of analysing beam vibrations are applied to a specific case. These solutions illustrate the effect of interlayer connection on the peak velocity of the beam vibrations. The proposed analytical theory is verified by tests and finite element calculations.     

Vibration analysis of a beam with partially distributed internal viscous damping

In this paper, governing equations of vibration for a beam with distributed internal viscous damping are established by using Timoshenko beam theory and Hamilton's principle. Then, the transfer matrix method is applied to obtain the frequency equations for the beam. The results reveal, when the internal viscous damping fully distributes along the beam, that the natural frequency decreases with the increasing damping and drops to a zero value at a certain critical damping. While the damping is locally distributed, damped frequency, mode shape and transient response time are affected most significantly by locating the damped segment at the position with maximum bending moment. The flexural amplitudes and phase angles of a beam excited by the resonant harmonic load can be effectively predominated by tuning the damping value.