一种利用等效模型与遗传算法的动态有限元模型修正方法

为了解决现有动态有限元模型修正方法计算效率不高或者可能获得局部最优解的问题,提出了一种利用等效模型和遗传算法的动态有限元模型修正新方法.首先,在设计参数的取值范围内,根据预设的多项式模型的阶次以及自变量的个数,利用试验设计方法获得拟合响应面模型所需要的最优样本点;通过有限元分析获得样本数据,并利用回归分析获得响应面模型,从而以响应面模型逼近结构特征与设计参数之间的函数关系.然后,在遗传算法的适应度评估环节,利用响应面模型替代有限元模型计算对应于一组设计参数的结构特征,并计算遗传个体的适应度,最终通过进化获得最优解,即为修正后的设计参数.以汽车车架模型为例,对其进行有限元分析与模态试验,并利用所提出的方法进行模型修正.修正后,模态频率误差的均方值小于2%.用修改后结构的动态特性的测试结果,对修正后有限元模型的预测能力进行检验,模态频率预测误差的均方值小于2%.     

模态参数的优化

为了对结构的动力学模型进行优化,文章提出了用原始结构的模态参数计算结构改变后的模态参数的灵敏度算法,建立了一种对结构进行多点动态修改的连续灵敏度优化分析方法.这种方法只需要模态参数作为初始数据,避免了确定结构物理参数,计算精度较高,易与各种优化方法结合,自动地寻找优化方向.最后以一个多自由度离散系统为例说明了方法的有效性和算法的正确性.     

稳态随机激励下结构阻尼系统的拓扑优化方法

该文对稳态随机激励下结构阻尼系统的拓扑优化问题进行了研究，提出了一种基于虚拟激励法的拓扑优化方法 .该方法中，自适应地确定用于模态叠加的低阶模态的数量.未知高阶模态的贡献由迭代算法近似得到.由于该方法可以提供结构响应解的近似显示表达式，不仅可以增强灵活性，还可提高计算效率.文中给出了数值算例，从计算精度和效率两个方面证实了该方案的有效性.     

使用稳定小波转换和神经网络识别功能梯度材料框架结构裂纹（英文）

目的:功能梯度材料(FGM)框架结构的裂纹识别。创新点:1.可接收多裂纹FGM结构在任意高频带中的精确模态。2.提出了一种使用稳定小波转换(SWT)模态和神经网络识别FGM框架结构裂纹的一体化程序。方法:使用动态刚度方法并结合与频率相关的形状函数,填补有限元方法的空白。这些形状函数被认为是频域内振动问题的精确解。结论:1.神经网络与SWT模态振型方法相结合,即使在测得的模态噪声很大的情况下,也能准确评估FGM结构的裂纹深度。2.本项研究中提出的FGM框架多裂纹识别一体化程序也适用于有限测量数据的情况,且这些数据不仅局限于模态,还包括结构的静态或动态挠度。     

考虑过阻尼模态参与的改进复模态叠加法（英文）

为处理非比例阻尼系统可能出现的过阻尼模态,提出了一种改进的复模态叠加强迫振动分析方法,建议无论模态是否过阻尼,复模态振动分析时应成对使用复模态．以一个连接任意布置外部阻尼器的悬臂梁典型非比例阻尼系统为例,其第1阶模态会随阻尼系数的增加而过阻尼．在厘清复模态响应与实际动力响应关系的基础上阐述了采用改进复模态叠加法获得时域响应、传递函数和方差的完整理论方法．将方程分为实部和虚部,使得原复数域运动方程成为基于实数矩阵的增广状态空间方程,从而克服了采用复数矩阵计算时变响应的困难．此外,针对基于白噪声滤波的外部激励,提出了一种高效方差响应评估方法,降低了计算资源消耗．结果表明,相较于假设模态法,复模态叠加法的结果更接近于有限元结果．基于遍历法研究最优阻尼器参数和位置时,采用多个小阻尼阻尼器优于单个大阻尼阻尼器．     

模态试验分析在教学中的应用和实践

模态试验分析是了解结构动态特性的有效手段.通过模态试验,可以计算出结构的固有频率、模态振型、阻尼比等参数,为结构设计与优化打下坚实的基础.在实验教学中,通过对模态试验的基本原理、主要步骤和试验中注意事项的介绍和分析,可以指导学生完成模态实验,加深学生对理论知识的理解和掌握,提高学生的动手能力、独立思考能力和分析解决问题的能力.     

基于部分反馈的LQG模态半主动控制算法

针对复杂结构半主动控制造价高、难以实现工程应用的缺点,对传统模态半主动控制算法改进并提出基于部分反馈的LQG模态半主动控制算法.算法中设计的Kalman滤波估计器可直接从结构的部分反馈信息对截断模态响应向量进行估计.通过在一安装有MR阻尼器的平板网架结构振动控制数值仿真表明,该算法对外部激励有很好的适应性,控制效果可以接近传统Clipped-optimal半主动控制算法,同时由于控制方程维数和所需传感器个数的降低,将更适合于复杂结构的工程应用.     

多功能滑板车侧轮架模态分析

以普通滑板车结构为框架,设计了一种具有载物能力的新式多功能滑板车,并对多功能滑板车新增的侧轮架进行了模态分析,得到了侧轮架的前五阶固有频率及对应振型,该方法和所得结果为多功能滑板车的动态设计提供了参考,同时也为多功能滑板车的动态响应计算和分析奠定了基础.     

矩阵分析在六点定位中的应用

从刚体运动学的角度,用矩阵变换理论,导出了误差计算矩阵式,该计算式可计算出零件上任意点的误差数值来.     

CW6163D型机床动态特性研究

通过对CW6163D型机床的激振试验,识别其模态参数和模态振型,掌握了该机床的结构动态特性,分析了该机床的薄弱环节.基于结合面基础特性参数,研究了机床导轨结合部特性的有限元建模方法,并将其用于机床整机的特性分析,为机床整机特性分析中结合部特性参数的确定提供了一种方法.通过有限元计算和试验模态分析的比较,证明两者能很好地吻合,为改善机床的动态特性提供科学的依据.     

Parametrically excited oscillation of stay cable and its control in cable-stayed bridges

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Parametrically excited oscillation of stay cable and its control in cable-stayed bridges

This paper presents a nonlinear dynamic model for simulation and analysis of a kind of parametrically excited vibration of stay cable caused by support motion in cable-stayed bridges. The sag, inclination angle of the stay cable are considered in the model, based on which, the oscillation mechanism and dynamic response characteristics of this kind of vibration are analyzed through numerical, calculation. It is noted that parametrically excited oscillation of a stay cable with certain, sag, inclination angle and initial static tension force may occur in cable-stayed bridges due to deck vibration under the condition that the natural frequency of a cable approaches to about half of the, first model frequency of the bridge deck system. A new vibration control system installed on the cable anchorage is proposed as a possible damping system to suppress, the cable parametric oscillation. The numerical calculation results showed that with the use of this damping system, the cable oscillation due to the vibration of the deck and/or towers will be considerably reduced. Project supported by National Natural Science Foundation of China (No. 59978044)     

提高隐式非线性微分方程的数值解算速度

非线性反馈控制系统的数学模式常常表现为隐式非线性微分方程,用通用数值积分法求解该系统的动态响应时,每步都要进行费时的矩阵求逆运算,使得解算速度大大下降.文中第一部分提出先求出隐式微分方程中时变矩阵A(x)逆的符号表达式,再用通用数值积分法求解该类系统时,每步积分不再求矩阵逆运算,从而可以大大提高解算速度.第二部分讨论了在MATLAB/Simulink新版本的各种环境下加速仿真速度的真实有效性.     

Dynamic response analysis of a moored crane-ship with a flexible boom

The dynamic response of moored crane-ship is studied. Governing equations for the dynamic response of a crane-ship coupled with the pendulum motion of the payload are derived based on Lagrange＇s equations. The boom is modeled based on finite element method, while the payload is modeled as a planar pendulum of point mass. The dynamic response was studied using numerical method. The calculation results show that the large-amplitude responses occur at wave periods near the natural period of the payload. Load swing angle is smaller for crane-ship with flexible boom, in comparison with rigid boom. The ship surge motions have large vibrations for crane-ship with flexible boom, which were not observed for a rigid boom. The analysis identifies the significance of key parameters and reveals how the system design can be adjusted to avoid critical conditions.     

振动压路机动力学分析之时域与频域法的比较

以振动压路机为例,对振动压路机压实过程建立了三自由度线性动力学方程,分别运用欧拉数值积分法和频域分析法进行了仿真.仿真结果显示,两种方法计算出的压路机系统响应结果一致.数值积分法所得的系统响应包含瞬态响应和稳态响应,计算时间长,对初始条件要求严格;而频域分析法得到的系统响应只有稳态响应,计算时间短,但对采样频率有一定的要求.     

基于ANSYS的高速包装机的椭圆齿轮模态分析

采用有限元法,建立了椭圆齿轮的动力学模型,通过有限元分析软件ANSYS对椭圆齿轮进行模态分析,得到了椭圆齿轮的前六阶固有频率和对应振型。该方法和所得结果为动态设计提供了参考,同时也为椭圆齿轮系统的动态响应计算和分析奠定了基础。     

Progressive collapse analysis of concrete-filled steel tubular frames with semi-rigid connections

A 9-story concrete-filled steel tubular frame model is used to analyze the response of joints due to sudden column loss. Three different models are developed and compared to study the efficiency and feasibility of simulation, which include substructure model, beam element model and solid element model. The comparison results show that the substructure model has a satisfying capability, calculation efficiency and accuracy to predict the concerned joints as well as the overall framework. Based on the substructure model and a kind of semi-rigid connection for concretefilled square hollow section steel column proposed in this paper, the nonlinear dynamic analyses are conducted by the alternate path method. It is found that the removal of the ground inner column brings high-level joint moments and comparatively low-level axial tension forces. The initial stiffness and transmitted ultimate moment of the semi-rigid connection are the main factors that influence the frame behavior, and their lower limit should be guaranteed to resist collapse. Reduced ultimate moment results in drastic displacement and axial force development, which may bring progressive collapse. The higher initial stiffness ensures that the structure has a stronger capacity to resist progressive collapse.     

非线性坝体地基系统的静动组合分析方法

为配合因考虑地基辐射阻尼作用和大坝坝体横缝非线性应分析方法和动接触力计算模型，该文建立了对非线性结构反映静动荷载耦合作用的静动组合计算方法，使得动接触力模型能够用于静力问题的计算，同时使得静力计算和采用波动模拟方法的动力计算能够统一、连续进行。     

Wind-induced stochastic response of controlled tall buildings by complex-mode analysis

This paper deals with the along-wind dynamic response of tall buildings passively controlled by Cross-Tensioned Spring Damper (CTSD) mechanisms. In order to estimate the dynamic response more accurately and efficiently, the building and its CTSD controllers were considered as a coupled non-classical damping system and a new stochastic response analysis method, complex-modal state-space method, was proposed based on the combination of complex modes of the structural system rather than on the real-modal decomposition as usual. As numerical examples, the displacement response of a 2-degree-of-freedom system to white-noise input is first considered and the validity and accuracy of the proposed method are demonstrated through comparison with the exact results. The wind-induced dynamic responses of a tall building controlled by two CTSD mechanisms are then analyzed. The calculation results showed that the proposed method is much more appropriate and accurate than the conventional real-modal decomposition method in the analysis of dynamic responses of passively controlled tall buildings. Project (59478034) supported by National Natural Science Foundation of China (NSFC).     

大体积混凝土施工技术及水化热引起裂缝的预防措施

根据工程施工特点对预测产生温度应力进行理论分析计算，从而制定底板大体积混凝土施工技术和预防裂缝措施，施工实践证明，只要满足配合比要求，严格控制混凝土内外温差，混凝土内部就不会由于温差和混凝土收缩而形成温度裂缝。