圆柱壳体基础隔振系统导纳功率流特性

针对圆柱壳体基础上动力装置隔振问题,建立复杂振源激励、多弹性支承、柔性圆柱壳体多维耦合传递矩阵力学模型。基于经典薄壳理论和模态叠加原理,同时计及奇偶模态响应,给出两端剪力薄膜支撑各向同性圆柱壳体的点导纳解析表达式,以导纳矩阵形式表征不同激励组分与速度响应的交叉耦合关系。考虑弹性支承的多维波动效应,运用子结构导纳法推导整体系统的功率流传递方程。研究表明:振源垂向、横向激励力与倾倒力矩诱发的隔振器纵向及弯曲谐振是中高频域系统功率流提高的主要原因;力矩激励对于柔性壳体基础功率流传输具有重要影响;壳体基础的径向弯曲振动在整个系统能量传递中占据支配地位,与其相关的弯曲机械波是主要结构声源。所用建模分析方法具有模块化延拓性,旨在为系统结构参数优化及后续的主被动一体化控制策略确立理论依据。     

浮筏隔振系统的功率流研究

利用功率流进行浮筏隔振系统研究。建立柔性基础上的多支承隔振系统动力学模型,给出系统动态特性结构化分析方法,推导耦合系统动态传递方程及功率流表达式。结合工程实际机组隔振系统功率流的数值计算结果,着重探讨隔振器安装位置、刚度及基础弹性对隔振效果影响。     

齿轮箱类系统的结构声功率流传递特性

以齿轮箱类复杂耦合系统为背景,推导“柔性振源齿轮轴-多维柔性轴承连接路径-柔性能量接受箱壁”的子系统导纳矩阵关系式,建立了系统的结构声功率流传递模型。建模过程中充分考虑了振源的力／力矩多维激励、振动功率流传递路径的柔性以及多维耦合特征。研究了齿轮箱不同的功率流传递路径及各路径之间的耦合特征,并对传递路径的柔性和引起箱体壁横向振动的功率流进行了定量分析。研究结果显示,该模型可方便地分析各子系统性能参数对整个耦合系统功率流特性的影响。     

齿轮箱类系统的结构声功率流传递特性

以齿轮箱类复杂耦合系统为背景,推导“柔性振源齿轮轴－多维柔性轴承连接路径－柔性能量接受箱壁”的子系统导纳矩阵关系式,建立了系统的结构声功率流传递模型。建模过程中充分考虑了振源的力/力矩多维激励、振动功率流传递路径的柔性以及多维耦合特征。研究了齿轮箱不同的功率流传递路径及各路径之间的耦合特征,并对传递路径的柔性和引起箱体壁横向振动的功率流进行了定量分析。研究结果显示,该模型可方便地分析各子系统性能参数对整个耦合系统功率流特性的影响。     

柔性基础非线性隔振系统动力学特性分析

建立了隔振对象-非线性隔振支承-柔性基础组成的耦合系统的一般性动力学模型,研究了应用振动功率流对非线性隔振系统进行效果分析的计算方法,给出了动力学方程初值问题表达式;并且基于Runge-Kutta法以某小型无人机的发动机隔振系统为算例,对几种非线性隔振器的隔振效果进行了数值仿真和分析。研究表明并联刚度隔振器和分段线性隔振器可有效减少隔振系统功率流的传递。     

功率流分析中的柔性振源子系统

针对多子结构耦合和多扰源激励的情况,以无约束自由子结构为基础,推导建立能充分考虑振源子系统柔性并能处理多扰源之间耦合的导纳矩阵公式.据此对工程中的浮筏隔振系统,推导新型的"机组-上层隔振器-浮筏"复杂柔性振源子系统导纳公式,建立新型的适用性更广的浮筏隔振系统模型,并进行实例研究分析.结果显示,当浮筏和基础板的刚性较高时,整个系统的低频特性主要取决于刚体耦合系统模态特性,而在中高频区系统动态特性更多受浮筏和基础板柔性模态的影响;适当增加振源子系统的柔性,可有效减少输入系统及基础的功率流.研究表明,扩展出的模型可方便地分析各子系统性能参数对整个耦合系统功率流特性的影响,可适应工程中不同情况的需要.     

分布参数双层隔振系统建模及其振动传递特性

从振动能量传递观点及工程实际隔振设计的角度出发,建立了中间连续筏体和中间分散质量两类双层隔振系统的解析模型。考虑连续筏体、隔振器及安装基础的分布参数特性,基于导纳矩阵理论对两类双层隔振系统的动态特性传递方程进行了理论推导。以功率流为价值函数揭示了系统振动传递机理并阐述了实际双层隔振设计需遵循的一般规律。实例研究表明：力矩激励在隔振系统能量传输中扮演着重要角色,应尽量减少力矩扰动带来的能量注入;在能耗效率及安装空间允许条件下,适当放大中间质量可获得更佳的隔振效果;中间筏体的柔性、隔振器的分布参数特性以及安装基础的非刚性因素使得中高频隔振性能恶化,采用中间分散质量方案可有效避免筏体柔性模态影响,并能显著降低隔振器驻波同柔性筏体模态间的耦合交互引起的能量峰值。     

分布参数双层隔振系统建模及其振动传递特性

从振动能量传递观点及工程实际隔振设计的角度出发,建立了中间连续筏体和中间分散质量两类双层隔振系统的解析模型。考虑连续筏体、隔振器及安装基础的分布参数特性,基于导纳矩阵理论对两类双层隔振系统的动态特性传递方程进行了理论推导。以功率流为价值函数揭示了系统振动传递机理并阐述了实际双层隔振设计需遵循的一般规律。实例研究表明:力矩激励在隔振系统能量传输中扮演着重要角色,应尽量减少力矩扰动带来的能量注入;在能耗效率及安装空间允许条件下,适当放大中间质量可获得更佳的隔振效果;中间筏体的柔性、隔振器的分布参数特性以及安装基础的非刚性因素使得中高频隔振性能恶化,采用中间分散质量方案可有效避免筏体柔性模态影响,并能显著降低隔振器驻波同柔性筏体模态间的耦合交互引起的能量峰值。     

基于功率流的双层隔振系统参数研究

以功率流隔振理论对双层隔振系统中的参数变化对基础振动的影响进行研究。将双层隔振系统简化为多个具有四端参数的理想机械系统的双层隔振系统功率流隔振模型,推导出各机械系统的四端参数,通过编写的双层隔振系统Mat lab应用程序,计算并绘制了隔振设备质量、隔振器刚度以及中间质量块质量等参数对传递基础功率流和振动速度的影响,研究表明:参数的改变对功率流变化影响较小;改变上层隔振器刚度和中间小质量块的质量可以调节二阶共振峰值的频率,提高二阶峰值后频带的隔振效果。     

准零刚度扭转隔振器振动传递特性研究

针对一种应用连杆弹簧负刚度结构所设计的正负刚度并联扭转隔振器,通过分析其设计参数,得到了其在静平衡位置达到准零刚度的条件。针对所述系统,建立二自由度非线性动力学微分方程,应用谐波平衡法求解了准零刚度隔振器的振动响应。考虑激励幅值、系统阻尼和转动惯量等因素,从扭转振动力矩传递和扭转振动功率流传递两个角度分析了准零刚度隔振系统的非线性振动传递特性。结果表明,此隔振系统具有良好的低频隔振效果,且表现为振动传递的硬特性;从功率流角度的分析还表明,系统的瞬时传递功率流峰值与输入功率流和耗散功率流的变化趋势保持一致。在低于共振区域的低频区间内,隔振系统前后两端的转动惯量对系统振动具有较大影响。最后,对扭转隔振器的振动隔离特性进行了试验验证,试验结果表明,隔振器具有良好的低频振动隔离特性。     

Effectiveness of a passive-active vibration isolation system with actuator constraints

In the prediction of active vibration isolation performance, control force requirements were ignored in previous work. This may limit the realization of theoretically predicted isolation performance if control force of large magnitude cannot be supplied by actuators.The behavior of a feed-forward active isolation system subjected to actuator output constraints is investigated. Distributed parameter models are developed to analyze the system response, and to produce a transfer matrix for the design of an integrated passive-active isolation system. Cost functions comprising a combination of the vibration transmission energy and the sum of the squared control forces are proposed. The example system considered is a rigid body connected to a simply supported plate via two passive-active isolation mounts. Vertical and transverse forces as well as a rotational moment are applied at the rigid body, and resonances excited in elastic mounts and the supporting plate are analyzed. The overall isolation performance is evaluated by numerical simulation. The simulation results are then compared with those obtained using unconstrained control strategies. In addition, the effects of waves in elastic mounts are analyzed. It is shown that the control strategies which rely on tmconstrained actuator outputs may give substantial power transmission reductions over a wide frequency range, but also require large control force amplitudes to control excited vibration modes of the system. Expected power transmission reductions for modified control strategies that incorporate constrained actuator outputs are considerably less than typical reductions with unconstrained actuator outputs. In the frequency range in which rigid body modes are present, the control strategies can only achieve 5-10 dB power transmission reduction, when control forces are constrained to be the same order of the magnitude as the primary vertical force. The resonances of the elastic mounts result in a notable increase of power transmission in high frequency range and cannot be attenuated by active control. The investigation provides a guideline for design and evaluation of active vibration isolation systems.     

Vibrational power-flow analysis of a MIMO system using the transmission matrix approach

The transmission matrix approach is employed in this paper for the vibrational power-flow analysis of a multiple-input/multiple-output (MIMO) system. The substructures in each subsystem are modelled as a group of general MIMO transmission elements, which are described in terms of discrete or distributed properties. The global transmission matrix of the system is formed by assembling the transmission matrices together. Using the proposed approach, the output variables of any subsystem can be expressed in terms of the input state variables of that subsystem. Hence, the proposed approach is very systematic in analysing the dynamic behaviour of a complex system with a group of elements. In the numerical example, the power flow of a multi-mount system is modelled analytically. The transmission of vibratory power flow from the vibrating rigid body into a simply supported plate through elastic mounts is studied in detail. The effects on the power flows of various factors, such as the plate thickness, loading type, mounting locations, and mass and damping properties of the mounts, are addressed.     

钟板对液压悬置特性的影响

为揭示钟板数量对液压悬置特性影响,首先,根据液压悬置结构搭建解耦膜、节流盘以及新节流盘液压悬置数学模型,同时分析钟板数量对液压悬置动态特性影响;其次,在高低频状态分析钟板数量对惯性通道、解耦膜通道流量以及上腔压力响应的影响;最后,分析节流盘和新节流盘液压悬置在钟板处的流量和压力响应。计算表明:低频时3种液压悬置的动态特性几乎相同,随着钟板数量增加悬置动态刚度和滞后角略有减小;在节流盘液压悬置的基础上增加钟板不影响解耦膜通道流量和上腔压力响应,但影响悬置的刚度和滞后角。     

Flexural ductility design of confined high-strength concrete columns: Theoretical modelling

Since the past few decades, high-strength concrete (HSC) has found increasingly wide applications in civil and structural engineering. Its utilisation is needed for the construction of buildings where reductions in self-weight and size of structural members are important. However, it was consistently reported that HSC exhibits undesirably lower ductility with the increase of concrete compressive strength. To restore the ductility, additional confinement has been recommended. This paper investigates the effectiveness of using Steel-Strapping Tensioning Technique (SSTT) to increase the flexural ductility of HSC columns. The effects of SSTT-confinement on the flexural ductility of HSC columns is studied by non-linear moment–curvature analysis. Based on such analysis, a parametric study was conducted to investigate the effects of various parameters, such as normalised axial force, normalised neutral axis depth, concrete compressive strength and confining volumetric ratio, on the flexural ductility of such columns. The results revealed that the flexural ductility of HSC columns is highly dependent on normalised axial force and neutral depth axis of the columns. It was found that the flexural ductility design of SSTT-confined HSC columns can be simplified by controlling the maximum allowable values of these parameters. Finally, two design equations were proposed for the flexural ductility design of such columns.     

Vibration control of a frame structure using electro-rheological fluid mounts

A squeeze-mode electro-rheological (ER) mount has been designed, manufactured, and applied to the vibration control of a frame structure subjected to external excitations. After verifying that the damping force of the ER mount can be controlled by controlling the applied voltage, a frame structure system supported by spring mounts and the proposed ER mounts has been assembled. The governing equation of the structural system is derived in the modal coordinate and is rewritten as a state-space control model. An optimal controller, which consists of the velocity feedback signal of the frame structure and the force feedback signal transmitted from the exciting point to the mount position, is formulated in order to attenuate the imposed excitations. The controller has been optimized experimentally and control responses such as the acceleration of the frame structure and the transmitted force at each mount position are presented in both time and frequency domains.     

Analysis of vibration power flow from a vibrating machinery to a floating elastic panel

A fully rigid–elastic-coupled dynamic model was developed for a vibration isolation system consisting of a rigid vibrating machinery, multiple resilient mounts and a floating elastic panel. This model was applied to investigate the vibration power transmission behavior of an X–Y motion stage-based system used in semiconductor wire-bonding equipment. The natural frequencies and modal characteristics of the system and its subsystems were numerically evaluated. The total power flow from the X–Y motion stage (the vibrating machinery) to the equipment table (the floating elastic panel) through multiple resilient mounts and the contribution of each force component at mounting junctions to the total power flow were analysed in the concerned frequency range for different types of excitations. The total power flow predicted by the developed model was also compared with that calculated using a conventional elastic support model. It was shown that the developed model provides a more accurate prediction of the total power flow in the frequency range of interest.     

车辆发动机悬架系统现状与进展

理想的发动机悬架系统应隔离发动机工作转速范围内由发动机干扰力所引起的发动机振动，并阻止由冲击而激起的发动机弹跳，这意味着发动机悬架的动态刚度和阻尼是与频率和振幅有关的，改善依赖于频率和振幅特性的动态刚度与阻尼是发动机悬架系统发展的关键所在。传统的弹性悬架不能满足所有的要求，它仅能在静偏转和隔振之间进行折衷，特别在低频域，被动的液压悬架能比弹性悬架提供更好的特性，通常半主动技术，由于其可调性而被用来进一步改善液压悬架的特性，为了隔振、低频时主动发动机悬架系统非常硬，而在高频域内被调整的非常软，主动的发动机悬架已被认为是发动机悬架的新一代，发动机悬架系统的优化是相当可取的，但发动机悬架的优化工作出现一些局限性，文中综述国内，外发动机悬架技术的现状与进展。     

Experimentelle untersuchungen an Koppelgetrieben mit LeistungsausgleichExperimental investigation of linkages with balancing of power

A summary is given of the methods for balancing of power in linkages.Three four-link mechanisms, mechanism A without balancing of power, mechanism B with balancing by a special distribution of the coupler mass, and mechanism C with balancing by flywheel, are investigated by experiment. The degree of irregularity, one bearing force, and the power input are measured. It is seen that mechanisms with balancing of power require a greater power input, although they have a motor torque with smaller fluctuation. Friction may not be neglected in the calculation of the coupler mass of mechanism B.There is a great difference between the calculated degree of irregularity and that found experimentally. Due to the balancing, the bearing forces increase; the foundation of mechanism B is excited to vibration. Mechanism C, with the flywheel, runs better, has less power input, and is cheaper to build, while mechanism B has less local demand and starting torque.