多层波纹钢板式干摩擦减振器实验研究

多层波纹钢板式干摩擦减振器具有结构简单、加工工艺好、减振效果显著等特点 ,具有广阔的应用前景 ,与传统的减振材料及结构相比 ,波纹钢板减振器具有耐高低温、耐腐蚀、承载能力更大、寿命更长以及可靠性更高等优点。本文研究了多层波纹钢板式干摩擦减振器制备工艺方法、动静态实验方法以及动静态特性 ,并研究了影响波纹钢板隔振性能的主要影响因素。实验结果表明 ,多层波纹钢板式干摩擦减振器具有良好的迟滞阻尼性能 ,减振器的刚度和能耗系数都随变形量的变化而呈非线性变化 :减振器的性能决定于钢板厚度、波纹高度、相对自由间隙和钢板层数等参数。对于不同参数的减振器 ,频响曲线的共振频率范围变化不大。该种减振器可以在较宽的频率范围工作。研究结果为多层波纹钢板减振器的进一步应用研究奠定了基础     

基于荷载时程分析法的钢板混凝土结构墙的抗冲击性能敏感性分析

选取由表面钢板、拉结筋、剪力钉及混凝土组成的钢板混凝土结构墙为研究对象,运用经典显式非线性动力分析软件ANSYS/LS-DYNA,基于荷载时程分析法进行了一系列影响钢板混凝土结构墙抗冲击性能的参数敏感性分析。这些参数包括:墙体厚度、钢板厚度、拉结筋直径与间距等。分析结果表明,以上参数均会影响墙体的抗冲击性能,尤其是墙体与钢板的厚度以及拉结筋的间距。本文的研究工作对于核电厂核岛厂房钢板混凝土结构外墙的设计具有一定的指导与参考意义。     

基于三维弹性理论的约束阻尼结构振动阻尼特性分析

本文根据三维弹性理论建立了多层弹性－粘弹性阻尼复合板自由振动的运动方程．该方程所根据的力学模型包括了影响阻尼复合板振动的几乎全部变形因素，包括弹性层和粘弹性层的平面剪切、横向剪切、纵向拉伸以及粘弹性层在厚度方向的胀缩变形。用该方程对工程声学问题所关注的中高频域结构损耗因子进行了数值计算。此外，对“附加型”和“成品型”两种结构型式约束阻尼板损耗因子的差异，尤其是阻尼层的厚度方向胀缩变形耗能对结构损耗因子的影响，进行了计算讨论。     

一种准零刚度系统隔振性能的几何参数优化分析

提出了一种采用菱形连杆组件作为负刚度机构的准零刚度隔振器(下文简称菱形准零刚度隔振器)。通过静力学分析方法,建立了菱形准零刚度隔振器数学模型,并与其他调节变量较少的隔振器模型进行了对比;以被测量曲线在隔振器平衡位置处的曲率作为评价参数,研究了负刚度机构几何参数对系统刚度、阻尼非线性的影响,推导了利用几何参数进行隔振优化的条件;采用谐波平衡法求解系统动力学方程,对隔振器在不同几何参数下的隔振性能进行了分析。结果表明:菱形准零刚度隔振器具有体积相对较小且非线性调节能力较好的特点,可通过调节杆长,或满足相关临界值条件时调节杆长偏差量(下文简称杆长差)对刚度及阻尼非线性特征进行优化;刚度与阻尼的非线性优化方向不同,但通常情况下,刚度非线性因素对隔振优化起主导作用;归一化振动相对位移小于0.1时,由刚度曲线曲率得到的临界值可以较好地作为杆长差参数的隔振优化调节依据。本文提出的非线性评价方法与几何非线性优化临界值计算方法,对于类似隔振器研究和设计具有一定的指导意义。     

双钢板混凝土组合板抗爆性能分析

钢-混凝土-钢组合板是一种新型的组合结构,与传统钢筋混凝土板相比,具有抗剪强度高、延性大、耗能能力强等特点,目前已经被广泛应用于核反应堆安全壳、海洋平台及储油罐等结构。本文中,设计并制作了缩尺的普通钢筋混凝土板和钢-混凝土-钢组合板,开展了在接触爆炸荷载作用下的实验研究,通过损伤分析、跨中最大挠度对比研究不同板的抗爆性能。基于ANSYS/LS-DYNA非线性有限元程序,研究了钢-混凝土-钢组合板的损伤模式、跨中最大挠度等,并与实验结果进行了对比分析,验证了有限元分析模型的准确性和适用性。参数化分析了炸药量、混凝土强度和钢板厚度等参数对钢-混凝土-钢组合板抗爆性能的影响规律。利用多参数回归分析方法,提出钢-混凝土-钢组合板跨中挠度的预测公式。结果表明:提高混凝土强度可以降低结构的塑性损伤, 增加钢板厚度可以有效降低钢-混凝土-钢组合板的跨中最大挠度。相对于普通钢筋混凝土板,钢-混凝土-钢组合板保持了良好的整体性,且具有继续承载的能力。拟合公式能够较好地预测钢-混凝土-钢组合板跨中挠度与药量和钢板厚度的关系。     

弧形双钢板混凝土组合板抗爆性能数值研究

依据规范设计了3种不同连接件的弧形双钢板混凝土组合板,基于ANSYS/LS-DYNA非线性有限元程序研究了弧形双钢板混凝土组合板在近场爆炸作用下的损伤模式、跨中位移变化以及能量消耗状况等,对比研究了3种不同板的耗能状况及损伤机理。以背爆面钢板跨中位移为指标,分析了用药量、混凝土强度和钢板厚度等参数对弧形双钢板混凝土板抗爆性能的影响规律。结果表明:在近场爆炸作用下,弧形板均保持良好的整体性,没有出现混凝土飞散现象,仍具有持续承载能力,比传统平面双钢板混凝土组合板具有更加优异的抗爆性能;重叠栓钉的连接性能强于栓钉,稍弱于对拉螺栓;提高混凝土强度不能改善混凝土的损伤状况,但能减小跨中位移;增加钢板厚度能显著减小钢板跨中位移,提高弧形双钢板混凝土组合板的抗爆能力。     

波形钢板-混凝土组合剪力墙的非线性有限元分析

以波形钢板-混凝土组合剪力墙的试验研究为基础,利用ANSYS建立了考虑黏结滑移的有限元模型;分析了混凝土墙体和波形钢板在试件加载过程中的受力性能,通过将有限元模型计算与试验所得的荷载-位移曲线进行对比分析,得出计算结果与试验结果吻合较好的结论。研究了栓钉对波形钢板和混凝土变形协调的影响,结果表明:墙体下部栓钉滑移量大于上部栓钉滑移量,可增大下部栓钉强度,以改善波形钢板和混凝土墙体的变形协调关系。分析了不同参数对波形钢板-混凝土组合剪力墙受力性能的影响,包括栓钉直径、栓钉间距、钢板厚度、墙体厚度、轴压比等。分析结果表明:增大栓钉间距会降低组合墙承载力和延性;栓钉直径、波形钢板厚度、配筋率对试件承载力影响不大;波形钢板厚度为2mm或轴压比为0.40时,试件延性明显降低;型钢厚度、墙体厚度、轴压比、剪跨比对试件承载力影响较大。     

车载系统主被动联合振动控制研究

针对车载系统行进过程中产生的结构振动,提出被动隔振和主动减振相结合的方法对结构弹性振动和刚体振动进行抑制．一方面,针对结构弹性振动,在车载结构和车体之间安装隔振装置,选择合适的隔振器参数,对车载结构的弹性振动进行隔离．另一方面,结合刚体振动抑制的需求,进一步研究小阻尼隔振器带来的结构低频刚体振动．对隔振器和车载结构形成的新系统采用主动控制方法设计最优控制器,对这一类过驱动控制系统进行主动控制研究．通过主被动控制结合,实现车载结构全频段范围内的振动抑制,能够将系统刚体振动的位移均方根值抑制到无控制时的5%以下．     

钢板混凝土梁的动力计算与抗爆分析

本文是将沿厚度由钢板和混凝土组合而成的钢板混凝土梁化为一等效横观备向同性构件。应用弹性动力学理论和复合板件等效非经典理论,通过动力分析,给出了基本动力方程和构件的等效折合弹性常数。并求得了钢板混凝土梁的固有频率和在横向爆炸载荷作用下的动力反应的解析解。文中对这类构件的力学特性及计算特点作了分析,其结果可直接用于钢板混凝土梁的各种动力及抗爆计算。     

新型橡胶隔振器参数辨识及动力学特性研究

采用粘弹性-超弹性-弹塑性材料本构模型,对一种新型的橡胶隔振器进行了动态特性研究,并与已有实验结果进行了对比。根据所得到的恢复力-位移迟滞回线,研究了频率、动态位移幅值对橡胶隔振器的动刚度的影响。在此基础上,给出了这种新型橡胶隔振器的非线性恢复力模型并进行了参数辨识。根据所得恢复力模型对隔振器系统进行了动力性能研究,发现此橡胶隔振器在低频时隔振作用很小,但在高频时隔振效果明显且随频率增加力传递率逐渐减小,隔振效果最大可达到96%。该隔振器的建模和参数辨识方法为这类隔振器的优化设计和工程应用提供了理论依据和分析方法。     

A quasi-zero-stiffness isolator with a shear-thinning viscous damper

Quasi-zero-stiffness(QZS) vibration isolators have been widely studied,because they show excellent high static and low dynamic stiffnesses and can effectively solve low-frequency and ultralow-frequency vibration. However, traditional QZS(T-QZS)vibration isolators usually adopt linear damping, owing to which achieving good isolation performance at both low and high frequencies is difficult. T-QZS isolators exhibit hardening stiffness characteristics, and their vibration isolation performance is e...     

Influence of excitation amplitude on the characteristics of nonlinear butyl rubber isolators

The purpose of this study is to explore the advantages and characteristics of nonlinear butyl rubber (type IIR) isolators in vibratory shear by comparison with linear isolators. It is known that the mechanical properties of viscoelastic materials exhibit significant frequency and temperature dependence, and in some cases, nonlinear dynamic behavior as well. Nonlinear characteristics in shear deformation are reflected in mechanical properties such as stiffness and damping. Furthermore, even when the excitation amplitude is small the response amplitude may often be large enough that nonlinearities cannot be ignored. The treatment involves developing phenomenological models of the effective storage modulus and effective loss factor of a rubber isolator material as a function of excitation amplitude. The transmissibility of a nonlinear viscoelastic isolator is compared with that of a linear isolator using an equivalent linear damping coefficient. Forced resonance vibration and impedance tests are used to characterize nonlinear parameters and to measure the normalized transmissibility. It is found that as the excitation amplitude of the nonlinear viscoelastic isolator increases, the response amplitude decreases and the transmissibility is improved over that of the linear isolator for excitation frequency that exceeds a particular value governed by the temperature and excitation amplitude. The method of multiple scales and numerical simulations are used to predict the response characteristics of the isolator based on the phenomenological modeling under different values of system parameters.     

Reducing force transmissibility in multiple degrees of freedom structures through anti-symmetric nonlinear viscous damping

In the present study, the Volterra series theory is adopted to theoretically investigate the force transmissibility of multiple degrees of freedom (MDOF) structures, in which an isolator with nonlinear anti-symmetric viscous damping is assembled. The results reveal that the anti-symmetric nonlinear viscous damping can significantly reduce the force transmissibility over all resonance regions for MDOF structures with little effect on the transmissibility over non-resonant and isolation regions. The results indicate that the vibration isolators with an anti-symmetric damping characteristic have great potential to solve the dilemma occurring in the design of linear viscously damped vibration isolators where an increase of the damping level reduces the force transmissibility over resonant frequencies but increases the transmissibility over non-resonant frequency regions. This work is an extension of a previous study in which MDOF structures installed on the mount through an isolator with cubic nonlinear damping are considered. The theoretical analysis results are also verified by simulation studies.     

无阻尼动力吸振器吸振的频率特性分析

本文分析了无阻层动力吸振器吸振的频率特性以及无阻尼动力吸振器参数的选择。同时还对此作了模型试验，试验结果与理论分析结果吻合。     

电子器件隔振设计实验研究

为了使精密电子产品在恶劣的环境下能够正常工作,必须对其采用适当的隔振措施。本文对某电子器件的三种不同隔振设计进行了试验研究,重点对比了不同设计在随机振动、正弦扫频振动环境下的隔振性能。试验结果表明,钢丝绳隔振器具有强的非线性特性,不同设计的隔振效果差异非常明显。采用阻尼板的设计方案,虽然隔振效果较好,但其加工难度较大,对使用环境要求较高。采用钢丝绳隔振器加铝质仪表板的设计方案,隔振效果较好,但由此带来其它的相关问题需要设计人员权衡考虑。     

几何非线性摩擦阻尼隔振系统动力学行为研究

非线性隔振系统由于具有较线性系统更优的隔振性能,因此在工程中应用广泛.本文通过配置与被隔振对象的运动方向相垂直的库伦摩擦阻尼器,构建了几何非线性摩擦阻尼模型.由于引入了几何非线性,因此其摩擦力与位移正相关,这与传统与位移无关摩擦力模型有显著不同.首先,建立了具有几何非线性摩擦阻尼的数学模型以及隔振系统的受迫振动方程;然后,使用谐波平衡法求解了动力学方程,并使用数值仿真方法验证了谐波平衡法求解的准确性;最后,研究了几何非线性摩擦阻尼隔振器的绝对位移传递率和相对位移传递率.研究结果表明,在库伦摩擦阻尼选择适当,非线性摩擦阻尼系统可以在保持高频振动衰减效果的前提下,显著降低系统共振峰,其性能优于传统的恒定摩擦阻尼隔振模型.同时,几何非线性摩擦阻尼系统能够避免传统摩擦阻尼系统中的“锁定”现象,从传递率角度来说,不利于共振峰控制;但从激励环境改变引发隔振系统失效的角度来看,几何非线性摩擦阻尼系统可以拓宽系统对激励幅值的适应范围,避免隔振系统失效.本文的研究结果对此类隔振系统的设计和摩擦阻尼参数的选择具有通用的指导意义.      

The energy thresholds of nonlinear vibration absorbers

A popular means to mitigate excessive structural vibrations is the attachment of a lightweight spring-mass element, known as a vibration absorber or tuned mass damper. Designing new types of vibration absorbers that outperform the classical linear tuned mass damper is a challenging ongoing research field. This paper focuses on the absorber with a strongly nonlinear spring characteristic. A critical aspect in the design procedure of such nonlinear vibration absorber is the existence of energy thresholds below which no efficient vibration reduction is possible. This paper extends the concept of an energy threshold to a more general parameter threshold representing several threshold values. Two important contributions are obtained. First, one single bifurcation analysis covers every combination of the system parameters. Second, the results are generalized to linear main systems under impulsive load and harmonic load, nonlinear main systems, and general nonlinear spring characteristics.     

Passive and active vibration isolation under isolator-structure interaction: application to vertical excitations

This work studies the influence of a vibration isolator on the response of a flexible base structure. Two strategies are compared: passive and active vibration isolation (PVI, AVI). Although the multiple advantages of AVI over PVI techniques are well known, their effect in the base structure has not to date been compared. This interaction has an important role in the performance of the general control system, especially when the vibration isolation system is not the only system on the base structure or when there are multiple isolators working simultaneously on it. In addition, the structural serviceability of the base structure can also be affected. The analysis of the vibration isolation problem is made from a wide perspective, including the effect that isolator has on the base structure. Hence assuming the base structure is a non-rigid system. The effect of the isolation system on the base response is studied for an extensive range of base structures, thus showing different possible scenarios. The influence is quantified by comparing the peak magnitude response of the base when both passive and active vibration isolation techniques are used. The theoretical results have been corroborated by undertaking experimental tests on a full-scale laboratory structure.

     

磁致伸缩主被动隔振装置中的磁机耦合效应研究

磁致伸缩材料和柔顺位移放大机构组成的主动驱动装置具有精度高、驱动力大等特点.将其与被动隔振装置并联,形成主被动隔振装置,可以弥补纯被动隔振在低频和微幅扰动工况下的不足.本文针对这类磁致伸缩主被动隔振装置进行磁机耦合效应研究.基于Jiles-Atherton模型,分析了磁致伸缩材料所受应力对有效磁场、磁化强度、磁致伸缩系数和材料杨氏模量的影响,表征了材料磁机耦合效应.在此基础上,建立了主被动隔振装置的动力学模型,分析了主动驱动装置与被动隔振装置间的耦合作用.在耦合作用影响下,若被动隔振装置刚度不同,即使输入磁场相同,驱动器产生的驱动位移和驱动力也不相同.磁致伸缩材料的变刚度效应使隔振装置整体等效刚度不再为定值,从而影响被动隔振效果.本文提出了通过柔顺机构参数设计减小前述两种耦合影响的方法.数值仿真结果表明,磁致伸缩主被动隔振装置在低于、接近和高于谐振频率三类扰动下,都能达到比被动隔振更好的振动抑制效果.此外,仿真结果验证了考虑磁机耦合效应的数值模型具有更高精度.      

Study on the force transmissibility of vibration isolators with geometric nonlinear damping

By a special layout of the damper in a vibration isolation system, the velocity-nth power damping of the damper can be transformed into the velocity-displacement dependent damping in the moving direction due to geometric nonlinearity. This study is mainly concerned with the mechanism of this geometric nonlinear damping and tries to find some guidelines for designing isolators with high performance, regardless of the isolator is passive or active. The model used in this study is an unconstrained two-degree-of-freedom isolation system, which is suitable for investigating vibration isolation in space vehicles. The motion equation is solved by the averaging method to obtain the amplitude–frequency equation. The influence of damping coefficients on the force transmissibility is analyzed. Results show that this kind of damping has some advantages in improving isolation performance at both the resonance and higher frequencies. Meanwhile, it can also degrade the isolation performance if unreasonable parameters are chosen.