应用于具有二次,三次非线性系统的增量谐波平衡法

本文导出了适用于具有二次、三次非线性的微分方程组的增量谐波平衡法，研究了扁拱的相加型和相减型的联合共振问题以及二自由度系统的强非线性振动问题，算例表明，增量谐波平衡法是一个求解多自由度系统强非线性振动的有效的半解析的数值方法。     

强非线性动力系统的频率增量法

提出一类强非线性动力系统的暧时频率增量法,将描述动力系统的二阶常微分方程,化为以相位为自变量、瞬廛频率为未知函数的积分方程;用谐波平衡原理,将求解瞬时频率的积分问题,归结为求解以频率增量的Fourier系数为独立变量的线性代数方程组;给出了若干例子。     

基于增量谐波平衡的参激系统非线性识别法

将增量谐波平衡法应用到非线性系统的建模和参数识别中,针对Mathieu-Duffing方程,推导了利用增量谐波平衡原理识别参数激励非线性系统参数的方法. 该方法改进了增量谐波平衡方法的推导过程,通过数值模拟对比研究了谐波平衡非线性识别(harmonic balance nonlinearity identification, HBNID)和增量谐波平衡非线性识别(incremental harmonic balance nonlinearity identification, IHBNID)的效果,验证了增量谐波平衡非线性识别的有效性. 结果表明,增量谐波平衡非线性识别的计算效率较高,计算精度和抗噪能力都优于谐波平衡非线性识别.      

强非线性系统的频闪法

本文给出了求强非线性系统周期解的频闪法,并给出了该方法的数学证明。     

具有非线性复刚度的复阻尼振动系统的摄动解

本文首次用摄动法获得了具有非线性复刚度的复阻尼振动系统的自由振动和强迫振动的解，并对这类问题作出了较为详尽的讨论，计算结果与试验结果几乎一致。     

一类强非线性系统周期解的能量迭代法

应用能量原理，引入牛顿线性化思想进行迭代，求强非线性Ｌｉｅｎａｒｄ方程的周期解。例子说明本方法行之有效且精度高。近似解析解表达式可借助计算机推出     

强非线性振动系统周期解的能量迭代法

对于完全强非线性系统：x^.. g(x) f(x,x^.)x^.=0,提出求周期近似解析解以及这些解的稳定性的新方法。式中，g(x)、f(x,x^.)x^.分别是x,x、x^.的非线性函数。方法是基于能量原理，求出其一次近似解析解，然后引进牛顿迭代思想，得到周期系统数微分方程，最后根据谐波平衡原理及最小二乘法求其高次近似解，高次近似解的表达式由计算机辅助推导。计算参考文献[2]和[3]中的例题，令其中ε=1，研究该完全强非线性系统的周期解及其稳定性，本文方法与龙格-库塔数值法算得的结果对照如图1-3所示，它们表明本文方法不仅有效而且精度较高。     

双稳态电磁式振动能量捕获器超谐波响应研究

超谐波响应是非线性振动系统在较大激励下表现的特性,在某种条件下双稳态振动能量捕获系统的超谐波响应可使系统产生优越的输出功率。本文将质量-非线性弹簧-阻尼系统与双稳态振动能量捕获器相结合,提出了附加非线性振子的双稳态电磁式振动能量捕获器,建立系统的力学模型及控制方程。采用两项式谐波平衡法,获得了双稳态系统在简谐激励下产生大幅运动的基谐波和超谐波响应的解析解,借助数值仿真分析了质量比和调频比对双稳态振动能量捕获器产生大幅运动的影响规律,获得了双稳态系统的结构参数的最佳配置范围,且当外部激励频率处于低频段时,系统发电主要表现为超谐波发电,随着激励频率的增大,振动发电系统主要呈现基谐波发电。上述研究,为双稳态能量捕获装置的理论研究提供了参考。     

非线性能量汇胞元减振效率分析

非线性能量汇(nonlinear energy sink, NES)具有减振频带宽、减振效果好等诸多优点.但是NES没有线性刚度的特征导致其难以驱动大重量的NES振子,从而难以应用于对大型工程结构的减振.因此,将NES以高效和便捷的方式应用于工程减振,仍然是有待研究的问题.将NES以胞元的形式装配于振动的主结构中,通过多个NES胞元的共同作用,是一种有前景的减振策略.文章在偏心转子激励下,探究了多个NES胞元对远大于单个NES自身重量的振动结构的减振效果,分析了多个NES胞元耦合主结构组成的系统的整体响应特征.建立了NES胞元减振系统的运动微分方程,采用复化平均法(complexification-averaging,CxA)导出系统的慢不变流形及稳态响应满足的近似解析表达式,通过慢变流形的扰动运动微分方程对稳态解进行稳定性分析,再利用伪弧长法获得系统响应的近似解,分析了NES胞元的减振规律及系统响应规律,最后利用龙格-库塔(Runge-Kutta, R-K)法进行数值验证.结果表明,通过多个NES胞元共同作用,能够有效控制较大重量的主系统振动,而且减振效率随NES胞元个数和重量的增加...     

谐和与随机噪声联合作用下非线性系统的响应

研究了Duffing振子在谐和与随噪声联合激励下的响应和稳应性问题。用谐波平均法分析了系统在确定性谐和激励和随机激励联合作用下的响应,用随机平均法讨论了随机扰动项对系统晌应的影响。在一定条件下,系统具有两个均方响应值和跳跃现象。数值模拟表明本文提出的方法是有效的。     

用IHB法分析双谐波激励下铰接塔-油轮系统的非线性动力学特性

研究了考虑平方阻尼情况下,铰接塔-油轮系统在双谐波激励下的非线性动力学特性.将该系统简化为单自由度分段线性恢复力,含平方阻尼的运动学分析模型,建立了铰接装载塔系统的分段非线性动力学方程.采用增量谐波平衡法获得系统周期解,使用Floquet理论判断系统的运动稳定性,结合路径跟踪法跟踪系统响应曲线,获得了系统所有可能的亚谐、谐波、组合谐波共振运动.分析了不对称恢复刚度比值对系统亚谐、组合谐波共振和对系统运动倍周期分岔点的影响,比较了考虑平方阻尼和不考虑平方阻尼情况下系统非线性动力学特性,得到了系统的一些重要的非线性动力学特点.     

Nonlinear Vibration of Plane Structures by Finite Element and Incremental Harmonic Balance Method

A nonlinear steady state vibration analysis of a wide class of planestructures is analyzed. Both the finite element method and incrementalharmonic balance method are used. The usual beam element is adopted inwhich the nonlinear effect arising from longitudinal stretching has beentaken into account. Based on the geometric nonlinear finite elementanalysis, the nonlinear dynamic equations including quadratic and cubicnonlinearities are derived. These equations are solved by theincremental harmonic balance (IHB) method. To show the effectiveness andversatility of this method, some typical examples for a wide variety ofvibration problems including fundamental resonance, super- andsub-harmonic resonance, and combination resonance of plane structuressuch as beams, shallow arches and frames are computed. Most of theseexamples have not been studied by other researchers before. Comparisonwith previous results are also made.     

研究强非线性振动问题的最简规范形方法

提出了一种应用最简规范形理论研究强非线性振动问题稳态渐近解的方法.最简规范形理论可以有效地化简传统规范形中的高阶项成分,复规范形方法的特点是简化矩阵分析的繁杂性,引入待定瞬时固有频率法则是将规范形理论的适用范围拓展至用于获取强非线性振动问题的稳态渐近解.结合上述特点,本文的改进方法克服了原有待定瞬时固有频率法在处理高阶传统规范形问题上遇到的计算复杂性问题.数值结果也表明本文方法更为简便、有效且具有更高的计算精度.     

一类强非线性机械基础系统的亚谐振动解析解

建立了机械基础动力系统的强非线性动力学模型，利用能量法对该系统的周期解进行了解析研究，确定了系统动态参数满足周期解的条件、系统的周期解以及解的稳定性判别式。发现了亚谐振动，并给出了系统在满足周期解条件下的一组参数对应的主振动、1／3亚谐振动和1／5亚谐振动。最后利用数值积分方法计算了系统在给定条件下的主振动及亚谐振动解，考察了解析解的正确性。     

Dynamic analysis of externally excited NES-controlled systems via a mixed Multiple Scale/Harmonic Balance algorithm

A general, nonlinear, multi-d.o.f.?structure, excited by harmonic external force in 1:1 resonance with one of the modes of the system, is considered. The structure is attached to an essentially nonlinear oscillator, with small mass and damping (Nonlinear Energy Sink, NES). The scope of the NES is to passively control the amplitude of vibrations of the main structure. A mixed Multiple Scale/Harmonic Balance Method (MSHBM) is proposed to get the differential equations describing the slow- and fast-flow dynamics of the whole structure. The main advantage of the procedure is that no complexification-averaging is required, so that the analysis is reconducted in the framework of the classical perturbation techniques.     

Study of the effects of cubic nonlinear damping on vibration isolations using Harmonic Balance Method

In the present study, Harmonic Balance Method (HBM) is applied to investigate the performance of passive vibration isolators with cubic nonlinear damping. The results reveal that introducing either cubic nonlinear damping or linear damping could significantly reduce both the displacement transmissibility and the force transmissibility of the isolators over the resonance region. However, at the non-resonance region where frequency is lower than the resonant frequency, both the linear damping and the cubic nonlinear damping have almost no effect on the isolators. At the non-resonance region with higher frequency, increasing the linear damping has almost no effects on the displacement transmissibility but could raise the force transmissibility. In addition, the influence of the cubic nonlinear damping on the isolators is dependent on the type of the disturbing force. If the strength of the disturbing force is constant and independent of the excitation frequency, then the effect of cubic nonlinear damping on both the force and displacement transmissibility would be negligible. But, when the strength of the disturbing force is dependent of the excitation frequency, increasing the cubic nonlinear damping could slightly reduce the relative displacement transmissibility and increase the absolute displacement transmissibility but could significantly increase the force transmissibility. These conclusions are of significant importance in the analysis and design of nonlinear passive vibration isolators.     

Perturbation of a Globally Stable Steady State and Uniform Persistence

In this paper we consider a parametrized family of semi-flows with continuous or discrete time. In the spirit of the global stability result proved by Smith and Waltman (Proc AMS 127:447–453, 1999) we use the upper semi-continuity of a parametrized family of global attractors. Here we investigate the case where the linearized equation of the unperturbed system has a simple dominant eigenvalue 0 in the case of a continuous time system (or 1 in the case of a discrete time system). New difficulties arise since such a system may exhibit a bifurcation. The goal of the paper is to describe the global dynamics of the perturbed system.      

粘弹层合板的稳态振动和层间应力

应用混合分层理论和Ressiner混合变分原理，在板厚方向取二次位移插值函数和三次、四次横向应力插值函数推导出粘弹层合板的动力学方程，得出简支粘弹层合板稳态振动的解。不仅得出与三层弹性板精确的自振频率吻合良好的解，而且对于粘弹层合板，所计算的自振频率和结构损耗因子也与三维结果吻合较好。计算了自由阻尼层合板对应的低阶法向位移响应幅值和层问横向应力的幅值。结果表明，较高的层间横向正应力是低频稳态振动中引起粘弹层合板分层破坏的主要因素，采用适当模量和厚度的粘弹性材料将有效地降低粘弹层合板的层间横向正应力的幅值。     

On Approximations of First Integrals for a System of Weakly Nonlinear,Coupled Harmonic Oscillators

In this paper a system of weakly nonlinear, coupled harmonic oscillatorswill be studied. It will be shown that the recently developedperturbation method based on integrating vectors can be used toapproximate first integrals and periodic solutions. To show how thisperturbation method works the method is applied to a system of weaklynonlinear, coupled harmonic oscillators with 1:3 and 3:1 internalresonances. Not only approximations of first integrals will be given,but it will also be shown how, in a rather efficient way, the existenceand stability of time-periodic solutions can be obtained from theseapproximations. In addition some bifurcation diagrams for a set ofvalues of the parameters will be presented.     

The Study of a Parametrically Excited Nonlinear Mechanical System with the Continuation Method

The dynamic behavior of a one-degree-of-freedom, parametrically excited nonlinear system is investigated. The Galerkin method is applied to the principal and fundamental parameteric resonance of the system. The continuation method is used to study the change of harmonic oscillation with respect to the variation of excitation frequency. The numerical stability analysis of the trivial solution is carried out and the stable and unstable regions of the trivial solution are given. They are found to agree with the results obtained by the analytical method of Galerkin. Periodic solutions are traced and the coexistence of multi-periodic solutions is observed With the change of excitation frequency the large amplitude periodic-2 oscillation is found to be in the same closed branch with the small amplitude periodic-2 solution. In addition, the bifurcation pattern of the trivial solution is found to change from subcritical Hopf bifurcation into supercritical Hopf bifurcation with the increase of excitation amplitude. Combined with the conventional numerical integration method, new complex dynamic behavior is detected.