RESPONSE OF PARAMETRICALLY EXCITED DUFFING-VAN DER POL OSCILLATOR WITH DELAYED FEEDBACK

The dynamical behaviour of a parametrically excited Duffing-van der Pol oscillator under linear-plus-nonlinear state feedback control with a time delay is concerned. By means of the method of averaging together with truncation of Taylor expansions, two slow-flow equations on the amplitude and phase of response were derived for the case of principal parametric resonance. It is shown that the stability condition for the trivial solution is only associated with the linear terms in the original systems besides the amplitude and frequency of parametric excitation. And the trivial solution can be stabilized by appreciate choice of gains and time delay in feedback control. Different from the case of the trivial solution, the stability condition for nontrivial solutions is also associated with nonlinear terms besides linear terms in the original system. It is demonstrated that nontrivial steady state responses may lose their stability by saddle-node (SN) or Hopf bifurcation (HB) as parameters vary. The simulations, obtained by numerically integrating the original system, are in good agreement with the analytical results.     

THE DYNAMIC PLASTIC RESPONSE CHARACTERISTICS OF CIRCULAR BEAM

In this paper the problem of a circular beam subjected to radial impact by a rigid massat its tip in its own plane is investigated on the basis of rigid-perfectly plastic assumption.The analytical solution of the particle velocities is obtained as the function of travellingplastic hinge location.By analysing the solution,some,some special properties of circular beamproblem are found.     

LARGE DEFLECTION DYNAMIC PLASTIC RESPONSE OF CLAMPED SQUARE PLATES WITH STIEEENERS

The large deflection dynamic plastic response of fully clamped squareplates with stiffeners under blast load is analyzed in detail in this paper. Variousrelevant motion patterns and criterions are presented. The formulas of maximumpermanent deformation of the plates with stiffeners are derived. The results ofcalculation are compared with those of experiment in [3], with good agreement shownin most cases.     

THE GENERAL SOLUTION FOR DYNAMIC RESPONSE OF NONHOMOGENEOUS BEAM WITH VARIABLECROSSSECTION

ＴＨＥＧＥＮＥＲＡＬＳＯＬＵＴＩＯＮＦＯＲＤＹＮＡＭＩＣＲＥＳＰＯＮＳＥＯＦＮＯＮＨＯＭＯＧＥＮＥＯＵＳＢＥＡＭＷＩＴＨＶＡＲＩＡＢＬＥＣＲＯＳＳＳＥＣＴＩＯＮＪｉＺｈｅｎ－ｙｉ（纪振义）（ＡｎｈｕｉＡｒｃｈｉｔｅｃｔｕｒａｌＩｎｄｕｓｔｒｙＣｏｌｌ...     

ANALYTICAL SOLUTIONS FOR RESPONSE OF COLLISION OF PARTICLE WITH CONICAL ROD CAUSED BY LONGITUDINAL VIBRATION

The objective is to present exact analytical solutions of longitudinal impact analysis for slender conical rods struck by a particle and a new method is proposed for conical rod-particle impact analysis, in which the superposition method is used and the response of the rod is presented. These analytical results are exact and can be used to validate the numerical methods or other analytical results. The numerical example shows that one of the advantages of the present method is that the analytical form is very simple. The result is that mass ratio and some variables describing the geometrical shape of rods such as taper, length and radius play an important role in impact dynamic system.     

ANALYSIS OF NONLINEAR DYNAMIC RESPONSE FOR VISCOELASTIC COMPOSITE PLATE WITH TRANSVERSE MATRIX CRACKS

I. INTRODUCTION The composite material and the composite structure are liable to generate damage during manufactureand under load, which will lead to a decrease of the material and structure’s mechanical properties.It is accepted that there exist four…     

A NEW METHOD FOR THE UNCERTAIN RESPONSE ANALYSIS OF STRUCTURES WITH UNCERTAIN PARAMETERS

A computing method for estimating the upper and lower bounds of the response ofstructures with uncertainties is presented.The uncertain parameters are described by the convexmodel.A numerical example of the frame structure is given to illustrate the effectiveness of thismethod.     

ASYMPTOTIC ANALYSES OF DYNAMIC RESPONSE OF HYPERBOLIC COOLING TOWER SHELLS WITH RING-STIFFENERS—PERTURBATION FINITE ELEMENT SOLUTION

In this paper,a new analysing method called perturbational finite element is suggested,by means of which we calculate the dynamic behaviour and response to turbulent wind ofhyperbolic cooling tower shell with ring-stiffeners.The results are compared with those offinite element numerical method and show that the method has the advantages of clearphysical idea and convenience of calculation and the accuracy of results is assured.     

ASYMPTOTIC ANALYSES OF DYNAMIC RESPONSE OF HYPERBOLIC COOLING TOWER SHELLS WITH RING-STIFFENERS—PERTURBATION FINITE ELEMENT SOLUTION

In this paper, a new analysing method called perturbational finite element is suggested, by means of which we calculate the dynamic behaviour and response to turbulent wind of hyperbolic cooling tower shell with ring-stiffeners. The results are compared with those of finite element numerical method and show that the method has the advantages of clear physical idea and convenience of calculation and the accuracy of results is assured. This paper was published in the second computational mechanics conference in Shanghai, China, Aug., 1986.     

THE QUALITATIVE ANALYSIS OF TWO SPECIES PREDATOR-PREY MODEL WITH ROLLING’S TYPE III FUNCTIONAL RESPONSE

This paper is denoted to the qualitative analysis of two species predator-prey model with Boiling’s type III functional response. Conditions for the global stability ofnontrivial equilibrium points and conditions for the existence and uniqueness of limit cycles around the positive equilibrium point are obtained. The biological interpretations of these conditions are discussed. The authors believe that the conditions established in this paper are new to literature.     

变化外形的水线对斜拉索风雨激振的激发作用

讨论变化外形的水线对斜拉桥拉索风雨激振的激发作用.首先,建立考虑水线外形变化的斜拉桥拉索风雨激振计算模型,并将由采用变化水线外形的模型得到的拉索最大振幅与固定水线外形模型的计算结果及试验实测结果对比,对模型进行验证;在模型得到验证的基础上,进一步讨论拉索和变化水线外形的水线振动稳定性及水线对拉索风雨激振贡献.计算结果表明,在四个典型工况下,考虑水线外形变化的模型得到的拉索计算振幅固定水线外形模型能更好地与试验实测振幅吻合;理论分析发现拉索速度和水线速度的耦合作用对水线运动的激发起到主导作用;水线的加速发散发生在拉索大幅激振之前.没有水线加速发散的时程中,拉索均不发生大幅激振.     

基于3自由度的新月形覆冰输电线舞动稳定性研究

针对覆冰输电线舞动问题提出了一种基于非对称空气动力系数矩阵的临界风速计算方法．基于拟静态理论得到覆冰输电线的气动载荷,该气动载荷考虑了横向运动以及扭转运动对相对风攻角的影响,最后建立等效的3自由度覆冰输电线舞动模型．在初始风攻角处对气动载荷进行泰勒展开,得到非对称的线性空气动力系数矩阵．结合3自由度振动方程以及非对称空气动力系数矩阵,采用Rourh-Hurwitz准则计算覆冰输电线舞动发生的临界风速．通过风洞实验测得新月型覆冰单导线的空气动力系数,根据本文提出的理论分析了竖向振动频率、面外振动频率以及扭转振动频率对临界风速的影响,最后与DenHartog理论得到的临界风速进行了对比．本文研究成果对于指导覆冰输电线路防舞设计具有理论意义．     

Dynamic method of determining aerodynamic characteristics of models from on experimental results obtained in short-duration wind tunnels

A technique is developed to recover the loads acting in model testing in short-duration wind tunnels. The model together with the load-measuring device is assumed to be a linear dynamic system. Normal responses of the system to unit loads are determined experimentally. The solution of a system of integral Volterra equations of the first kind is found in the class of piecewise-constant functions. Examples are given on solving a test problem with a known exact solution and a problem of determining the aerodynamic characteristics of the HB-2 reference model on the basis of loads obtained in wind-tunnel measurements. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 5, pp. 47–55, September–October, 2006.     

THEORETICAL AND EXPERIMENTALRESEARCH ON DYNAMIC BEHAVIOR OF GUYED MASTS UNDER WIND LOAD

I. INTRODUCTION Wind-induced vibration is the critical factor for the safety of guyed masts. Many dynamic modelshave been proposed in the literature[1 , 2]. However, there are obvious de?ciencies in many of theseprevious works owing to the poor cabl…     

Response analysis of randomly excited nonlinear systems with symmetric weighting Preisach hysteresis

An approximate method for analyzing the response of nonlinear systems with the Preisach hysteresis of the non-local memory under a stationary Gaussian excitation is presented based on the covariance and switching probability analysis. The covariance matrix equation of the Preisach hysteretic system response is derived. The cross correlation function of the Preisach hysteretic force and response in the covariance equation is evaluated by the switching probability analysis and the Gaussian approximation to the response process. Then an explicit expression of the correlation function is given for the case of symmetric Preisach weighting functions. The numerical result obtained is in good agreement with that from the digital simulation. The project supported by the National Natural Science Foundation of China (19972059) and Zhejiang Provincial Natural Science Foundation (101046)     

Eigenfrequency analysis of cable structures with inclined cables

The approximate eigenfrequencies for the in-plane vibrations of a cable struc- ture consisting of inclined cables,together with point masses at various points were com- puted.It was discovered that the classical transfer matrix method was inadequate for this task,and hence the larger exterior matrices were used to determine the eigenfrequency equation.Then predictions of the dynamics of the general cable structure based on the asymptotic estimates of the exterior matrices were made.     

Aerodynamic control of bridge cables through shape modification: A preliminary study

This paper examines the viability of modifying bridge cable shape and surface for the purpose of controlling wind-induced vibrations. To this end, an extensive wind-tunnel test campaign was carried out on various cable shapes about the critical Reynolds number region. Cable shapes were chosen to passively modify the flow in a particular manner. Tested shapes included those which have some form of waviness, faceting and shrouding. Section models were tested using a static inclined rig, allowing them to be installed at yawed cable-wind angles for both smooth and turbulent flow conditions. The aerodynamic damping of the tested cylinders is evaluated by applying both 1- and 2-dof quasi-steady aerodynamic instability models. This allows for the prediction of regions of aerodynamic instability, as a function of flow angle and Reynolds number. Whilst the plain, wavy and faceted cylinders are predicted to suffer from either dry inclined galloping, “drag crisis” or Den Hartog galloping, the shrouded cylinder is found to be stable for all angles of attack, albeit with an increase in drag at typical design wind velocities. Finally, turbulent flow is found to introduce an increased amount of aerodynamic damping mainly by providing a more constant lift force over tested Reynolds numbers.     

不同自由度下覆冰四分裂导线舞动特征分析

基于哈密顿变分准则,推导了单档导线的振动控制方程,通过建立的气动荷载模型得到考虑气动荷载影响的覆冰导线舞动控制方程．进行风洞试验并得到覆冰四分裂导线的三分力气动系数,利用泰勒定律将气动系数在攻角α = 0处展开,得到了气动系数的三次拟合曲线．采用摄动法求解了二自由度下覆冰导线的位移响应,接着采用数值法求解了三自由度下覆冰导线的位移响应．最后,通过具体的数值算例分析了两者位移响应的区别．算例分析表明：二自由度下覆冰导线的位移响应与三自由度下覆冰导线的位移响应存在一定的区别,三自由度下覆冰导线的舞动更符合导线真实状态下的舞动,其结果更具有参考价值．