宽度方向附加局部磁约束阻尼条的夹心板的振动特性

在柔性结构的减振处理中,传统被动无磁约束减振(PCLD)方法已被广泛采用,但是由于阻尼材料特性受温度和频率的影响,其减振效果受到限制。而采用在约束层上设置永磁体的方法(MCLD)可使阻尼层达到比传统约束阻尼处理方法更高的剪应变,从而增强粘弹层的阻尼耗能,提高低阶模态的减振效果。针对悬臂板的(m=1,n=1)、(m=2,n=1)的两阶扭转模态,在这两阶的方向上的节线y=B/2处设置永磁体,节线两侧设置磁约束阻尼层,研究MCLD的阻尼改进效果及规律。研究表明,在悬臂板的自由端铺设磁阻尼层时,能有效地提高阻尼减振效果;另外,对不同阻尼层的宽度,MCLD仍具有提高阻尼的能力。     

玻璃钢约束阻尼复合结构的阻尼特性

以玻璃纤维增强树脂作为约束层主要材料、丁腈橡胶为阻尼层、钢板为基板制备约束阻尼复合结构, 运用动态黏弹谱仪和悬臂梁共振法, 研究温度、约束层刚度和阻尼层结构对约束阻尼复合结构减振效果的影响。结果表明:自由阻尼复合板的最大阻尼范围落在阻尼层的玻璃化转变区;玻璃钢约束层能将复合结构的阻尼拓展至阻尼层的高弹态区域, 增加阻尼层厚度可以提高约束复合板的阻尼性能;提高孔隙率同样有利于约束复合板阻尼性能提升;铝板约束层提升作用尤为显著, 然而在海洋环境、干湿交替等强腐蚀场合中, 铝板极易腐蚀而丧失约束功能, 因此在这类特殊场合下耐腐蚀的玻璃钢具有优势。      

含弹性与阻尼约束的隔振系统动力学设计

从非线性动力学角度提出一种含弹性和阻尼约束隔振系统的设计方法。该方法先设计满足工作频带内传递率的小阻尼线性隔振系统，再基于对主共振的奇异性理论分析设计约束刚度、约束阻尼和间隙，最后运用周期解延续、插值胞映射等数值方法检验设计的可靠性及各种裕度指标。因靠约束阻尼抑制共振传递率，故工作频带内的传递率可设计得很低。     

多层板式电涡流阻尼器构型与磁路优化分析

为提升板式电涡流阻尼器(PECD)的耗能效率,对比分析了单层与多层PECD典型构型的紧凑性与材料利用率,发展与完善了多层PECD构型与磁路优化设计。基于某单排式多层PECD样机阻尼性能测试结果,校验了三维电磁场有限元稳态分析法预测PECD等效阻尼系数的精度;仿真分析获得了永磁体与导体铜板之间的磁场间隙、永磁体的固定材料、间距与布置方式等参数对多层PECD等效阻尼系数的影响规律,据此提出了多层PECD的优化构型与磁路。结果表明:与单层PECD相比,多层PECD耗能效率得到有效提升,结构也更为紧凑;磁场间隙及永磁体的固定材料、布置方式与间距等对PECD等效阻尼系数均有显著影响,其中磁场间隙、相邻永磁体磁极布置与间距等存在最优参数。多层PECD的优化构型与磁路为:磁场间隙宜尽可能减小;采用非导磁材料固定永磁体;同侧永磁体宜阵列布置;永磁体沿阻尼器运动方向磁极宜相反布置,间距取0.2倍永磁体同向尺寸;永磁体沿垂直于阻尼器运动方向磁极宜相同,且间距越小越好。     

基于负刚度机构的高刚度-超阻尼隔振器设计与研究

为能够隔离作用在负载上的直接扰动并提高系统的阻尼特性以避免产生共振,提出一种采用磁性负刚度机构设计的超阻尼隔振系统,其由磁性负刚度机构和两对相互对压的机械弹簧并联构成;磁性负刚度机构由五块沿轴向磁化的环形永磁体构成,倾斜环形永磁体被对称地固定在基础上,运动的环形永磁体由对压的机械弹簧约束,并沿轴向发生相对运动;根据电流模型,推导了磁性负刚度机构的磁性恢复力以及磁性负刚度解析表达式;通过将隔振系统中的刚度单元和阻尼单元重新布置并引入一个内部隐性自由度,该系统被设计成与线性参考系统具有相同静刚度、相同质量以及相同阻尼的超阻尼装置;分析了该装置中刚度单元、阻尼单元以及永磁体附加质量对所设计系统阻尼、固有频率和主系统振动响应的影响。研究结果表明,所提出的隔振系统具有高刚度和超阻尼特性,能够有效抑制主系统的振动;在高频段,主系统的响应将收敛于线性参考系统。     

基于负刚度机构的高刚度-超阻尼隔振器设计与研究EI北大核心CSCD

为能够隔离作用在负载上的直接扰动并提高系统的阻尼特性以避免产生共振,提出一种采用磁性负刚度机构设计的超阻尼隔振系统,其由磁性负刚度机构和两对相互对压的机械弹簧并联构成;磁性负刚度机构由五块沿轴向磁化的环形永磁体构成,倾斜环形永磁体被对称地固定在基础上,运动的环形永磁体由对压的机械弹簧约束,并沿轴向发生相对运动;根据电流模型,推导了磁性负刚度机构的磁性恢复力以及磁性负刚度解析表达式;通过将隔振系统中的刚度单元和阻尼单元重新布置并引入一个内部隐性自由度,该系统被设计成与线性参考系统具有相同静刚度、相同质量以及相同阻尼的超阻尼装置;分析了该装置中刚度单元、阻尼单元以及永磁体附加质量对所设计系统阻尼、固有频率和主系统振动响应的影响。研究结果表明,所提出的隔振系统具有高刚度和超阻尼特性,能够有效抑制主系统的振动;在高频段,主系统的响应将收敛于线性参考系统。     

约束阻尼对二维声学黑洞薄板减振特性的影响

声学黑洞（Acoustic Black Holes,ABH）以结构厚度的幂律变化实现弹性波的汇聚,结合阻尼层能较好地抑制结构振动。为进一步实现结构的低频振动控制,将声学黑洞与约束阻尼复合,建立附加约束阻尼的二维声学黑洞薄板模型,采用数值方法计算加速度响应与结构损耗因子,研究二维声学黑洞板附加约束阻尼后的减振特性,并通过二维声学黑洞薄板振动试验开展验证,最后探究约束层材料、厚度及约束阻尼半径对声学黑洞板低频减振性能的影响规律。结果表明：相比于附加自由阻尼,约束阻尼使声学黑洞薄板在第一阶共振峰处的加速度导纳降低12.61 dB;当约束层厚度为截断厚度的2倍左右时,薄板整体可以达到较佳的减振效果。研究可为声学黑洞薄板结构的低频减振应用提供重要参考。     

影响约束阻尼结构阻尼性能的因素

采用自由梁振动法,研究阻尼层厚度、约束层材料及环境温度等三个变量,对约束阻尼结构阻尼性能的影响。结果表明：阻尼层厚度在1 mm～4 mm范围内,约束阻尼结构的阻尼性能随阻尼层厚度的增加而降低; 约束层材料分别为钢板、大理石板、砂浆板时,约束阻尼结构的阻尼性能不同;低温、高温环境均使约束阻尼结构阻尼值变小; 常温环境下,约束阻尼结构的阻尼值较大,复合损耗因子超过了0.154。     

附加约束阻尼层的复合材料梁单元建模分析

复合材料空心圆截面梁是桁架和刚架结构中大量采用的常用构件，而实践证明约束阻尼层能有效改善复合材料空心圆截面梁的动力学特性，但传统的约束阻尼层结构有限元计算方法需要大量的单元，这给大型复杂结构的计算带来了巨大的困难。本文采用Timoshenko梁假定。建立了一类附加约束阻尼层复合材料空心圆截面梁弯曲的数学模型。应用Hamilton原理。采用三节点高次梁单元对构件进行离散化。建立了附加约束阻尼层复合材料空心圆截面梁的梁单元。同传统的锥壳单元相比，该方法极大地减少了计算时间。用实验验证了本文计算结果的正确性。同时也分析了约束层厚度对损耗因子的影响。     

约束阻尼层在输电塔风振控制中的应用

约束阻尼层是机械及航空工程中常用的阻尼减振方法之一。讨论了在1 000 kV特高压输电线路典型钢管塔应用约束阻尼层的风振控制问题。首先给出了粘弹性阻尼材料的基本力学特性和约束阻尼层的两种有限元建模方法。通过ANSYS对一简单约束阻尼层结构采用两种不同有限元模型进行数值仿真分析比较,给出了在ANSYS中准确模拟这类结构的途径。应用这一建模方法对钢管塔主材安装约束阻尼层后的减振效果进行了数值仿真。结果表明,在主材设置约束阻尼层后杆塔一阶纵向和一阶横向弯曲模态阻尼比均有较大提高,但扭转模态的模态阻尼比提高很少。时域风振分析表明,设置约束阻尼层后塔顶的顺风向加速度响应显著降低。最后从结构及阻尼层的模态应变能角度建议了阻尼材料及约束阻尼层设置部位的选取原则。     

Dynamic characteristics of cylindrical hybrid panels containing viscoelastic layer based on layerwise mechanics

The viscoelastic damping model of the cylindrical hybrid panels with co-cured, free and constrained layers has been developed and investigated by using the refined finite element method based on the layerwise shell theory. The transverse shear and normal strains and the curved geometry are exactly taken into account in the present layerwise shell model, which can depict the zig-zag in-plane and out-of-plane displacements. The damped natural frequencies, modal loss factors and frequency response functions of cylindrical viscoelastic hybrid panels are compared with those of the base composite panel without a viscoelastic layer. The difference in the free vibration and damping of the thin and thick composite laminates and the viscoelastic sandwiched beam between full and partial layerwise theories is verified by comparison with the published results. Various damping characteristics of cylindrical hybrid panels with free viscoelastic layer, constrained layer damping, and co-cured sandwich laminates are investigated. Present results show that the full layerwise damping model accurately predicted the vibration and damping of the cylindrical hybrid panels with viscoelastic layers.     

Experimental study on vibration and damping of curved panel treated with constrained viscoelastic layer

This paper presents experimental investigation on the damping effects of constrained layer damping treatment on a curved panel. Vibration attenuation of the curved panel is achieved by attaching constraining layer damping patches at the optimal locations. The placement strategies of constrained layer patches are devised using the modal strain energy (MSE) method. Locations for application of damping patches are those, where modal strain energy is maximum for the particular mode. The treatment is then applied to the elements that have highest MSE in order to target specific modes of vibrations. Extensive experiments are conducted by making number of separate samples of viscoelastic and constrained layer damping patches for each configuration to damp different modes simultaneously or independently. The experimental results demonstrate utility of the modal strain energy technique as an effective tool for selecting the locations of the constrained layer damping treatment to achieve desired damping characteristics over a broad frequency band.     

Active constrained layer damping of geometrically nonlinear vibration of rotating composite beams using 1-3 piezoelectric composite

In this paper, an analysis for active constrained layer damping (ACLD) of rotating composite beams undergoing geometrically non linear vibrations has been carried out. Commercially available vertically/obliquely reinforced 1-3 piezoelectric composite (PZC) material has been used as the material of the constraining layer of the ACLD treatment. A finite element (FE) model has been derived to carry out the analysis. The substrate beam is considered thin and hence, first order shear deformation theory (FSDT) and von-Karman type nonlinear strain–displacement relations are used to derive the coupled electromechanical nonlinear FE model. The rotary effect has been suitably modelled by incorporating extensional strain energy due to centrifugal force. The Golla–Hughes–McTavish method has been employed to model the constrained viscoelastic layer of the ACLD treatment in the time domain. The numerical responses revealed that the ACLD treatment with 1-3 PZC constraining layer efficiently performs the task of active damping of geometrically nonlinear vibrations of the rotating composite beams. The effects of the fibre orientation angles of the angle-ply substrate beams and the 1-3 PZC constraining layer on the ACLD of the geometrically nonlinear vibrations have been investigated. Also, the effect of the thickness variations of the 1-3 PZC layer and the viscoelastic constrained layer on the damping characteristics of the overall rotating composite beams has been studied.     

阻尼加强筋板架减振性能试验研究

基于试验模态分析,考察船用加强筋板架模型在不同敷设位置,全部进行约束阻尼等处理方式对系统动态特性的影响。试验结果表明:(1)板架表面进行约束阻尼处理后,在不同测点位置,结构表面振动均有不同程度的衰减;(2)阻尼减振作用与激励源传播距离有关,在激励点位置,阻尼减振效果不佳;(3)阻尼减振效果与激励方式、阻尼敷设位置均有一定关系,局部阻尼处理在特定情况下可达到与全部阻尼处理相当的减振效果。     

Sandwich-fabric panels as spacers in a constrained layer structural damping application

Sandwich-fabric panels can provide for an alternative spacer material in a constrained layer damping configuration. Constraining layer configurations with sandwich-fabric spacers can be a weight efficient replacement for full composite constraining layers, if the shear stiffness of the rubber used is not too high. It seems that in any case the use of sandwich-fabric spacers can lead to a more cost-effective damping treatment. To predict the damping of multilayer materials a strain energy method was used. The damping of multilayer beams could be accurately modelled by calculating the distribution of strain energies in the structure with the help of finite elements and knowledge of the loss factors of the individual layers (as a function of frequency).     

磁橡胶约束阻尼处理的激励力有效区域研究

着重分析磁橡胶约束阻尼处理方法（MRLD)的阻尼效果受激励力影响的原因。基于MRLD与传统约束阻尼处理（PCLD)不同的耗能机制,得到这两种阻尼处理方式下系统耗能量的比值,进而估算MRLD相比PCLD,其阻尼改进效果中存在的激励力有效区域的大致范围。研究表明,材料损耗因子b不仅决定激励力有效区域的范围,同时也决定MRLD所能达到的阻尼改进效果的最优值。     

Hybrid damping of smart, functionally graded plates using piezoelectric, fiber-reinforced composites

This paper deals with the investigation of active, constrained layer damping (ACLD) of smart, functionally graded (FG) plates. The constraining layer of the ACLD treatment is considered to be made of a piezoelectric, fiber-reinforced composite (PFRC) material with enhanced effective piezoelectric coefficient that quantifies the in-plane actuating force due to the electric field applied across the thickness of the layer. The Young's modulus and the mass density of the FG plates are assumed to vary exponentially along the thickness of the plate, and the Poisson's ratio is assumed to be constant over the domain of the plate. A finite-element model has been developed to model the open-loop and closed-loop dynamics of the FG plates integrated with two patches of ACLD treatment. The frequency response of the plates revealed that the active patches of ACLD treatment significantly improve the damping characteristics of the FG plates over the passive damping. Emphasis has been placed on investigating the effect of variation of piezoelectric fiber angle in the constraining layer of the ACLD treatment on the attenuating capability of the patches. The analysis also revealed that the activated patches of the ACLD treatment are more effective in controlling the vibrations of FG plates when the patches are attached to the surface of the FG plates with minimum stiffness than when they are attached to the surface of the same with maximum stiffness.     

减振型阻尼钢轨有限元分析

利用有限元ANSYS软件对6种阻尼结构钢轨进行谐响应分析,通过比较加速度-频率响应曲线以及结构的损失因子,确定最佳阻尼设计方案。分析结果表明：采用约束阻尼处理技术制成的减振型钢轨有良好的减振效果;在较宽的频率范围（0-5000Hz）内获得较好的减振降噪效果,再综合经济、加工难易等因素,得到约束层厚度为3cm、阻尼层厚度为2cm以及约束材质为铝材是较为合理的。     

The damping of sandwich cantilever beam

Abstract

The natural vibration damping of sandwich cantilever beam has been investigated. A theoretical development for damping calculation has been carried out by considering shear force, normal force and bending moment for both face and core layers. The ratio of thickness between the face and core layer is not constrained. Experimental results show that theoretical calculation is quite satisfied. When the elastic modulus of the core layer is larger than that of the face layer, a simpler and more convenient formula has been developed to calculate the loss factor.