有多阶固有频率要求的组合结构设计

在各子结构的振协固有特性已知下，通过设计子结构间的连接元件，使得组合结构的多阶固有得到满足，在组合结构动力重分析中，以胳子结构的剩余附着模态作为基保留模态的补充，进行模态缩减，保了计算的精度，提高了计算速度。对具有刚体模态的子结构采取了移频处理技术，文中给出的两个设计计算实例，表明本文方法的有效性。     

一种满足多阶固有频率和节线位置等要求的结构动力学设计方法

在给定了多阶固有频率、振型节线位置、结构的质量与质心等要求条件下，运用优化方法进行结构动力学设计，文中还给出了一种振型节线的直接搜索法，且对一个实际的机翼颤振模型进行了设计。     

一类单塔斜拉桥固有频率及模态的计算与分析

采用连续体系统动力学分析方法对一类平面单塔斜拉桥的固有频率及模态进行了计算与分析。桥面两端简支,并由一个刚性的塔和两根斜拉索支撑。将桥面简化成梁的模型,建立了各斜拉索及各梁段的动力学偏微分方程、斜拉桥的边界条件及子结构间的几何与力学相容条件。推导了斜拉桥线性化、无阻尼系统的频率方程。考虑斜拉桥左右对称及参数(斜拉索长度、初始垂度)微小变动导致对称性破缺的情况,数值求解不同参数下斜拉桥的固有频率及对应的模态。结果表明:斜拉桥第3阶和第4阶固有频率相差不到0.1%,具有密集固有频率的现象;斜拉桥对称性破缺前后第3阶和第4阶固有频率随参数变化的曲线具有频率曲线偏转现象,第3阶和第4阶模态间存在模态跃迁现象。该研究结果可在斜拉桥设计和建造过程中起参考作用。     

基于实测频响函数的子结构模态综合

本文以梁型结构串联布局为应用背景,研究了导纳综合法的试验模态分析.探讨了界面自由度的选取、刚体模态的处理、预测阻尼比的可能性以及影响预测精度的因素.物理梁试验结果表明,导纳综合法能精确地预测组装结构的频响函数和所需的模态参数.     

组合结构有限元模型的分步实验校正

本文从结构有限元建模实际情况出发，提出了一个组合结构有限元分析模型的分步实验校正方法。分析模型的误差主要归于两类：一是某些子结构因局部形状复杂；经过分简化而引起。二是各子结构间连接参数估计不准而引起。为此，建议分步校正，先利用子结构动态实验数据，修正子系统阵中与简化处相关的局部物理参数，再由组合结构的动态实验数据，修正子结构间连接参数，从而完成整体有限元模型的修正。导出了修正公式，给出了修正算法。     

轨道系统高频振动分析的动态子结构法

提出了包含钢轨断面弹性变形、轨下不连续支承、横垂向交叉导的轨道高频振动分析模型。根据轮轨特点,提出适合轮轨高频振动分析的阻抗聚缩法。预测结果与试验结果吻合较好。分析表明约８００Ｈｚ以下,钢轨振动表现为整体振动,再高频率钢轨发生断面弹性变形的振动。我国轨道系统第一、第二、阶二振频率分别为１５０Ｈｚ和３２０Ｈｚ,ｐｉｎｎｅｄ－ｐｉｎｎｅｄ共振频率的１２８０Ｈｚ。     

循环对称结构的模态参数计算方法

利用循环对称结构部件模态的等同性，推求了循环对称结构中的混合型动态子结构法的综合方程。     

固有频率集聚时处理振型的一个方法

1.前言现在作固有振动分析的结构愈来愈复杂了。由此带来的困难不仅在于自由度众多,还在于常有频率集聚现象,即在很小一段频率区间内有很多个固有频率。当频率集聚在一起时,相应的固有振型对结构的某些物理参数变化很敏感。在正问题中,例如用有限元模型计算固有频率和振型,由于这种敏感性,刚度阵与质量阵的某些误差就会导致计算所得的集聚组振型有更大的误差;在反问题中,集聚组对应的振型对测量误差很敏感,因而也难     

频率方程有重根的主振型问题

针对自由振动体系的频率方程有重根解的现象，利用矩阵秩的判断对体系进行讨论，给出实例分析，绘出了振型图．     

An investigation into natural vibrations of fluid–structure interaction systems subject to Sommerfeld radiation condition

A fluid-structure interaction system subject to Sommerfeld＇s condition is defined as a Sommerfeld system which is divided into three categories： Fluid Sommerfeld （FS） System, Solid Sommerfeld （SS） System and Fluid Solid Sommerfeld （FSS） System of which Sommerfeld conditions are imposed on a fluid boundary only, a solid boundary only and both fluid and solid boundaries, respectively. This paper follows the previous initial results claimed by simple examples to further mathematically investigate the natural vibrations of generalized Sommerfeld systems. A new parameter representing the speed of radiation wave for generalized 3-D problems with more complicated boundary conditions is introduced into the Sommerfeld condition which allows investigation of the natural vibrations of a Sommerfeld system involving both free surface and compressible waves. The mathematical demonstrations and selected examples confirm and reveal the natural behaviour of generalized Sommerfeld systems defined above. These generalized conclusions can be used in theoretical or engineering analysis of the vibrations of various Sommerfeld systems in engineering.     

An evolutionary search technique to determine natural frequencies and mode shapes of composite Timoshenko beams

Natural frequencies and mode shapes of composite Timoshenko beams are determined by a diversity guided evolutionary algorithm (DGEA) with different boundary conditions. After applying boundary conditions, frequency equation is obtained in determinant form. Then, natural frequencies and consequently mode shapes are obtained using DGEA where the absolute value of determinant is the subject of optimization. Advantages of employing DGEA are: first, all natural frequencies are produced in a simple run, second, its simplicity for implementation and third, the procedure is not computationally prohibitive. Results clearly show the applicability of the proposed method for obtaining natural frequencies and mode shapes.     

The effect of dynamical self-orientation and its applicability for identification of natural frequencies

The effect of dynamical self-orientation and its applicability for the identification of natural frequencies of the investigated systems is demonstrated in this paper. Unidirectional vibration exciter is fixed to the investigated systems via a pivot link and can rotate around it. It is shown that the exciter changes its orientation in the steady state motion mode when the frequency of excitation sweeps over the fundamental frequency of the examined system. Approximate analytical analysis of the discrete system illustrates the basic principle of the effect of dynamical self-orientation. Numerical analysis of both the discrete and different continuous elastic systems confirms the applicability of the effect of self-orientation for the identification of natural frequencies.     

有频率、振型节线位置要求的结构动力学优化设计

本文提出了一种同时满足固有频率、振型节线位置等要求的结构动力学设计方法。该方法先建立了振型节线位置及变化与独立设计参数的关系，然后在某些约束下利用优化方法求解设计结果，文中同时还给出了模态空间中固有频率、振型灵敏度分析的数值计算方法。实例表明它能有效地解决一些工程结构设计时涉及到固有频率、振型节线位置要求的结构动力学设计问题。     

A new approach to perturbation analysis of vibration modes with close frequencies

This paper presents a new method for perturbation analysis of vibration modes with close frequencies. The main idea of this method is to transform the perturbation analysis problem of vibration modes with close frequencies into a perturbation problem associated with repeated frequencies. A numerical example is given to demonstrate the good agreement of eigensolutions obtained by this method with the exact solutions.This project is supported by National Natural Science Foundation of China     

Efficient methods free of irregular frequencies in wave and solid/porous structure interactions

The method of boundary integral equation is widely applied to compute and analyze wave–structure interactions in marine and offshore engineering, and the application is also seen in marine aquaculture to deal with waves and porous structure interactions. The application of the Fredholm integral equation of the second kind together with the free-surface Green function for a surface-piercing body suffers from irregular frequencies which may be confused with resonance peaks. A simple and efficient method to remove irregular frequencies in the wave–structure interactions is developed via enforcing null potential (and horizontal derivatives) on discrete points on the interior water-plane area and is referred to as overdetermined integral equations (and enhanced overdetermined integral equations), respectively. Structures with solid surface, porous surface and their blending are considered, and numerical results demonstrate the effectiveness of this method. In contrast to extended integral equations, the overdetermined integral equations are easy to implement and more time-efficient.     

Determining the natural frequencies of highly inhomogeneous shells of revolution with transverse strain

A method of studying the natural vibrations of highly inhomogeneous shells of revolution is developed. The method is based on a nonclassical theory of shells that allows for transverse shear and reduction. By separating variables, the two-dimensional problem is reduced to a sequence of one-dimensional eigenvalue problems. The inverse iteration method is used to reduce these problems to a sequence of inhomogeneous boundary-value problems solved by the orthogonal sweep method. The capabilities of the method are illustrated by solving certain representative problems and comparing their solutions with those obtained using the three-dimensional theory of elasticity, the classical theory of shells, and the refined Timoshenko model __________ Translated from Prikladnaya Mekhanika, Vol. 43, No. 9, pp. 38–47, September 2007.     

传热结构的多目标拓扑优化设计研究

深入分析了传热结构多目标拓扑优化设计中的几个关键问题。提出了基于结构柔度最小化和结构散热弱度最小化的多目标拓扑优化设计方法,建立了传热结构的多目标拓扑优化设计模型,推导了传热结构多目标拓扑优化中用于迭代分析求解的优化准则算法和敏度分析方程。通过数值计算验证了理论和算法的有效性。     

Higher order sensitivities in structural static design

I.IntroductionStructuraldesignplaysoneofthemostimportantrolesinthefieldofaeronauticsandastronautics.Itsessenceisaninversealgebraiceigenvalueproblem.Whenwe'resolvingthiskindofproblems,sensitivity(theeigenvaluesandeigenvectorsderivativeswithrespecttodesignp…     

对称结构动力学设计中的广义逆特征值问题

将对称结构动力学设计问题归结为一类含设计参数的广义逆特征值问题,以结构的动态特性指标作为设计准则来设计结构,通过建立等效的非互性方程组,利用ｎｅｗｔｏｎ法求解其设计参数,使得到的结构具有满足设计要求的动态特性。数值全题表明本文方法有很好的效能。