动载荷时域半解析识别方法

基于模态空间转换、离散数据最小二乘拟合与模态叠加原理,提出一种动载荷时域半解析识别方法。通过模态空间转化将动载荷识别问题转化为模态坐标函数识别问题,以结构特性参数与已知自由度上的动响应为输入,利用最小二乘拟合得到模态坐标的拟合函数,根据叠加原理与结构动力学控制方程,识别出结构时域动载荷。分别用计算仿真与试验测试得到的时域加速度响应作为输入,实现时域动载荷的识别。识别结果与真实动载荷对比表明,本文的识别方法能较准确地识别结构动载荷值及载荷作用部位。     

冲击载荷识别的瞬态统计能量分析方法

提出了一种基于瞬态统计能量分析理论的冲击载荷识别新方法。利用该方法,首先由系统能量平衡方程确定冲击载荷的作用位置及相应的输入能量,在常值假设条件下根据识别的输入能量反演得到冲击载荷的幅值谱,在此基础上,对于给定的冲击载荷时域波形形式,提出一种参数拟合方法用于最终重建冲击载荷的时间历程。通过一个两板耦合结构系统的冲击载荷识别对识别方法进行了实验验证研究。结果表明冲击载荷识别的瞬态统计能量分析法能够准确地识别冲击载荷的作用位置和输入能量,在冲击波形已知的假设条件下可以较为准确地重建冲击载荷的时间历程,从而为实际工程中的冲击载荷识别提供了一条可行途径。     

动态载荷激励位置识别技术研究

以简支梁为研究对象,提出了一种动态载荷激励位置识别的“最小判定系数法”。预估载荷虚拟激励位置,择优选取两组加速度响应并在频域内识别虚拟激励位置处的两组当量动载荷,令其差值为最优化目标变量,则最小目标变量对应的一组虚拟激励位置即为载荷真实激励位置。仿真和实验结果表明该方法正确、可行。     

复杂耦合动力系统振动响应的统计估计方法研究

复杂耦合动力系统是一种常见的工程力学系统,分析了复杂耦合动力系统振动响应的统计估计问题.首先通过动态系统的统计能量分析(SEA)方程,应用扰动法推导随机系统的能量平衡方程,进而推导复杂耦合系统响应的统计估计公式.在分析复杂耦合系统的响应统计估计时,重点分析各种形式激励对系统响应统计估计的影响以及载荷参数的确定方法.分析表明,相互独立的载荷作用是相关载荷作用时的一种特殊情况,它们可以应用统一的计算公式来表达.根据建立的响应统计估计方法,设计了相应的试验件,验证其正确性,试验结果表明,应用该推导得到的理论公式,系统响应的相对偏差能有效的减小,得到的能量平均值能够与试验值较好地吻合.     

基于频响函数辨识机械结合部动态参数的研究

摘要：进行机械结构的动力分析与动态优化设计时,为获得比较准确的结构边界条件,结合部参数辨识成为其中一项关键技术。结合工程实际,应用频响函数辨识结合部刚度与阻尼参数的方法进行参数识别,对能否获取完备频响函数进行了研究,并作出相应的求解策略。该方法避开了对频响函数直接求逆,运用最小二乘原理将矛盾方程转化为定解方程,保证了数值计算的稳定。一般情况下,结合部处绝对阻尼值要远远小于绝对刚度值,为了更准确地辨识出阻尼值,需采用对阻尼进行二次辨识。该方法具有一定的工程实用价值,而且辨识过程简单。算例证实了该方法具有很高的辨识精度。     

后缘小翼智能旋翼减振效果影响因素分析

建立了带后缘小翼智能旋翼气动弹性载荷计算模型及减振优化分析方法。模型考虑刚体后缘小翼的气动力与惯性力对弹性桨叶系统的影响,使用粘性涡粒子法结合翼型查表法计算旋翼气动载荷,采用力积分法计算桨叶与桨毂载荷,构造了包含桨叶根部扭转及桨毂振动载荷为目标函数的优化问题,基于最速下降-黄金分割组合优化算法寻找最佳小翼偏转规律。研究发现,建立的后缘小翼载荷控制方法有效,可降低振动目标函数70%。桨叶的弹性扭转使后缘小翼能有效实施减振,但弹性扭转对小翼气动力矩的放大作用使减振时通常伴随着桨叶扭转载荷增大的现象。     

HGT准双曲面齿轮承载传动误差的优化设计

承载传递误差曲线的波动程度可反映出齿轮副的动态性能,波动幅值越大,噪音越大;波动幅值越小,噪音越小,传动越平稳。首先以局部综合法(Local Synthesis)为基础,并依据格里森准双曲面齿轮的加工原理,对HGT准双曲面齿轮进行了加工参数设计。在此基础上以传动比函数的一阶导数m'_21和接触迹线与根锥的夹角η_2为优化变量,以承载传动误差幅值最小为目标函数,通过遗传算法对加工参数进行优化设计,以提高齿轮副的动态特性。研究发现:①当大轮加载扭矩分别为800N·m和1500N·m时,优化后承载传动误差幅值分别降低了37.92%和16.57%;②为了保持齿轮副较好的振动特性,应使其尽量在局部最小幅值对应的载荷附近工作,且随着︱m'_21︱的增大,局部最小幅值向大载荷方向移动,说明要使齿轮副具有较小的承载传动误差幅值需要较大的载荷。     

结构损伤与荷载的快速同步识别方法研究

本文仅以损伤因子为优化变量,提出一种结构损伤和荷载同步识别的方法。首先通过时域荷载识别的方法将未知荷载转化为损伤因子的函数,将近似荷载作用下的结构响应和实测响应的平方距离作为目标函数,从而降低了需要识别未知参数的数目;然后在目标函数的计算过程中,利用虚拟变形法（VDM）可进行结构快速重分析的思想,快速构造给定损伤因子下系统的脉冲响应,避免每步迭代重新集装系统矩阵,并通过荷载形函数方法进一步提高荷载识别的效率;最后利用二次多项式插值近似结构每个时刻的响应方法和推导对应目标函数的梯度表达式来提高优化搜索的速度。本文利用刚架模型进行数值模拟,准确识别了结构中柱子单元刚度损伤、附加质量以及梁上的未知移动荷载,并通过一个悬臂梁试验进一步验证所提出方法的准确性和可行性。     

汽车排气系统吊耳动刚度优化方法的研究

基于汽车排气系统吊耳传递的动态载荷最小、吊耳耐疲劳性最好,建立了考虑动力总成在内的排气系统振动分析模型。进行了排气系统的自由模态和约束模态的测试,并和计算值进行了对比分析,证明了所建立的排气系统振动模型的正确性。以吊耳的垂向动态载荷最小和其静变形量在一定范围内为优化目标,建立了排气系统吊耳动刚度优化模型。优化后,在怠速工况和2档全负荷加速工况下对车身底板驾驶员位置进行了振动响应测试,测试结果表明,利用优化后的吊耳刚度,能够有效降低车身底板的振动加速度,表明了阐述的排气系统建模和吊耳动刚度优化方法的有效性。文中建模与优化方法,对排气系统的吊耳动刚度计算与优化具有指导意义。     

变质量提升系统钢丝绳轴向-扭转耦合振动特性

为了掌握变质量提升系统的振动特性,考虑提升钢丝绳的扭转运动并根据变质量非完整系统的Ham ilton原理建立了钢丝绳轴向和扭转耦合振动数学模型,并推导了变质量提升系统振型函数及确定轴向与扭转耦合振动频率的超越方程,给出了基于振型函数随系统质量变化及固定不变两种情况下变质量提升系统钢丝绳振动位移、张力和扭矩响应的求解方法。以矿井提升箕斗装载为工况进行应用分析,结果表明:两种求解方法得到的响应基本接近;提升容器装载过程是一个质量增大振动频率减小的过程,钢丝绳的动位移、张力和扭矩以波动形式逐渐增加。装载量较大时可采用振型函数固定的方法计算装载提升系统的频率和响应,冲击较大的载荷建议考虑提升容器的波动载荷,从而有助于提高计算效率和增强提升系统的安全可靠性。     

Precise identification of moving vehicular parameters based on improved glowworm swarm optimization algorithm

This paper proposes an indirect method for the identification of moving vehicular parameters using the dynamic responses of the vehicle. The moving vehicle is modelled as 2-DOF system with 5 parameters and 4-DOF system with 12 parameters, respectively. Finite element method is used to establish the equation of the coupled bridge–vehicle system. The dynamic responses of the system are calculated by Newmark direct integration method. The parameter identification problem is transformed into an optimization problem by minimizing errors between the calculated dynamic responses of the moving vehicle and those of the simulated measured responses. Glowworm swarm optimization algorithm (GSO) is used to solve the objective function of the optimization problem. A local search method is introduced into the movement phase of GSO to enhance the accuracy and convergence rate of the algorithm. Several test cases are carried out to verify the efficiency of the proposed method and the results show that the vehicular parameters can be identified precisely with the present method and it is not sensitive to artificial measurement noise.     

The probability density evolution method for dynamic response analysis of non‐linear stochastic structures

The probability density evolution method (PDEM) for dynamic responses analysis of non‐linear stochastic structures is proposed. In the method, the dynamic response of non‐linear stochastic structures is firstly expressed in a formal solution, which is a function of the random parameters. In this sense, the dynamic responses are mutually uncoupled. A state equation is then constructed in the augmented state space. Based on the principle of preservation of probability, a one‐dimensional partial differential equation in terms of the joint probability density function is set up. The numerical solving algorithm, where the Newmark‐Beta time‐integration algorithm and the finite difference method with Lax–Wendroff difference scheme are brought together, is studied. In the numerical examples, free vibration of a single‐degree‐of‐freedom non‐linear conservative system and dynamic responses of an 8‐storey shear structure with bilinear hysteretic restoring forces, subjected to harmonic excitation and seismic excitation, respectively, are investigated. The investigations indicate that the probability density functions of dynamic responses of non‐linear stochastic structures are usually irregular and far from the well‐known distribution types. They exhibit obvious evolution characteristics. The comparisons with the analytical solution and Monte Carlo simulation method demonstrate that the proposed PDEM is of fair accuracy and efficiency. Copyright © 2005 John Wiley & Sons, Ltd.     

Crack identification of beam structures using homotopy continuation algorithm

An approach based on homotopy continuation algorithm is presented to identify the parameters of a cracked beam. Euler–Bernoulli finite beam element with a fully opened crack model is adopted to establish the dynamic equation of the structural system. In the inverse problem, the homotopy equation is derived from minimizing the error between the calculated and the simulated measured acceleration responses. The range of homotopy parameter is divided into a number of divisions. Newton iterative method is employed to estimate the solution at each of these division points. The solution at the last division point corresponds to the homotopy equation matching the objective function. Numerical simulations with a simply supported beam and two-span beam show that the proposed method is very accurate compared to an existing method for both single and multiple cracks identification. The effects of type of excitation, division of the homotopy parameter and measurement noise on the identified results are discussed. It is noted that there is no need for an accurate set of initial values with the proposed approach.     

电阻应变数据采集系统传递函数的评价

提出了电阻应变数据采集系统传递函数的一种辨识方法,给出了详细技术过程,包括:电阻应变阶跃激励源的构建与赋值,电阻应变阶跃信号波形的获取,应变放大器恒定时间延迟的测量估计,用等效采样方式获取电阻应变数据采集系统的阶跃响应序列,激励序列和响应序列的时序统一与合成,用一种特殊白化滤波器的最小二乘法进行电阻应变数据采集系统传递函数辨识等。在一组实验中的传递函数辨识应用,证明了该方法的有效性及可行性。该方法可用于电阻应变数据采集系统动态特性的计量校准,及其传递函数辨识。     

Dynamic response and reliability analysis of structures with uncertain parameters

An original approach for dynamic response and reliability analysis of stochastic structures is proposed. The probability density evolution equation is established which implies that incremental rate of the probability density function is related to the structural response velocity. Therefore, the response analysis of stochastic structures becomes an initial‐value partial differential equation problem. For the dynamic reliability problem, the solution can be derived through solving the probability density evolution equation with an initial value condition and an absorbing boundary condition corresponding to specified failure criterion. The numerical algorithm for the proposed method is suggested by combining the precise time integration method and the finite difference method with TVD scheme. To verify and validate the proposed method, a SDOF system and an 8‐storey frame with random parameters are investigated in detail. In the SDOF system, the response obtained by the proposed method is compared with the counterparts by the exact solution. The responses and the reliabilities of a frame with random stiffness, subject to deterministic excitation or random excitation, are evaluated by the proposed method as well. The mean, the standard deviation and the reliabilities are compared, respectively, with the Monte Carlo simulation. The numerical examples verify that the proposed method is of high accuracy and efficiency. Moreover, it is found that the probability transition of structural responses is like water flowing in a river with many whirlpools, showing complexity of probability transition process of the stochastic dynamic responses. Copyright © 2004 John Wiley & Sons, Ltd.     

基于欧进萍谱的广义Maxwell耗能结构随机响应简明解法

针对设置广义Maxwell阻尼器多自由度耗能结构在欧进萍谱激励下响应分析较复杂的问题,提出了一种求解系统响应简洁的解析解法.将广义Maxwell阻尼器本构方程、原结构运动方程与欧进萍谱滤波方程联立,重构结构运动方程;采用复模态法将其解耦,得到结构位移及结构速度、层间位移及层间速度、阻尼器受力及其变化率等响应基于白噪声激...     

Nonlinear Dynamic Characteristics and Optimal Control of Giant Magnetostrictive Laminated Plate Subjected to In-plane Stochastic Excitation

In this paper, nonlinear dynamic characteristics and optimal control of giant magnetostrictive laminated plate (GMLP) subjected to in-plane stochastic excitation were studied. Von del Pol nonlinear item was introduced to interpret the hysteresis phenomenon of the strain–magnetic field intensity curve of giant magnetostrictive material, and the nonlinear dynamic model of GMLP subjected to in-plane stochastic excitation was developed. Local and global stochastic stabilities were analyzed according to largest Lyapunov exponent theory and singular boundary theory. The functions of steady-state probability density and joint probability density were obtained, and the condition of stochastic Hopf bifurcation was analyzed. The reliability function was solved from backward Kolmogorov equation, and the probability density of the first-passage time was obtained. Finally, the optimal control strategy was proposed in stochastic dynamic programming method. Numerical simulation shows that the stability of the solution varies with parameter, and stochastic Hopf bifurcation appears in the process; the reliability of the system was improved by optimal control, and the first-passage time was delayed. The result is helpful to engineering applications of GMLP.     

The Chebyshev norm as a deterministic alternative for problems with uncertainties

The problem of determining, for a dynamic system, the absolute optimum response characteristics when portions of the system are not fully prescribed, and the best and worst possible performance when the excitation is uncertain is formulated as a mathematical programming problem with equality and inequality constraints. The objective is to extremize the maximum time value of a response, i.e. a Chebyshev norm is employed. A linear example problem and its solution are presented to illustrate the formulation.     

黏弹性隔震系统非均匀与完全非平稳地震响应解析分析

为建立设置支撑的实用黏弹性阻尼器耗能结构及阻尼器系统的抗震动力可靠度分析方法,提出了在非扩阶空间上,基于非均匀和完全非平稳地震激励下,设置支撑的实用黏弹性阻尼器耗能隔震系统响应的通用解析解。对于设置支撑的实用黏弹性阻尼器做等效变换,并建立隔震结构系统的运动方程,在非扩阶空间上获得系统在任意激励和非零初始条件下瞬态响应的非正交模态叠加精确解。基于地震动的强度非平稳和频率非平稳,获得了耗能隔震结构位移、速度,阻尼器受力、受力速度,支撑位移、速度以及阻尼器位移、速度的非平稳均方响应通用解析表达式,并具体得到经典均匀与非均匀调制非平稳随机地震激励和C-P完全非平稳地震动功率谱模型的具体响应解析解。通过结构系统各响应基于该方法的频响函数与直接求解的频响函数对比验证了该方法的正确性。该分析方法的建立为设置支撑的实用黏弹性阻尼器耗能结构及阻尼器系统的抗震动力可靠度分析乃至抗震设计方法的研究提供了一套新的分析途径。     

基于相关函数矩阵及卷积神经网络的结构健康监测研究

环境激励下利用时域振动响应构建的内积矩阵是结构健康监测中一种较好的结构特征参数。为了提升结构健康监测方法的识别准确率,构建内积矩阵时往往需要较多的振动响应测点,这将直接影响方法的工程实用性。该文基于时域振动响应的相关性分析理论,将内积矩阵扩展到了相关函数矩阵,实现从少量的振动响应测点中获取更多的结构健康特征信息,以降低结构健康监测方法对测点数量的需求。进一步结合卷积神经网络优异的数据特征提取能力,以相关函数矩阵为输入、结构健康状态为输出,提出了基于相关函数矩阵及卷积神经网络的结构健康监测方法。典型航空加筋壁板螺栓松动监测的实验研究结果表明,仅采用结构上任意2个测点的时域振动响应,该文方法针对螺栓松动位置的识别准确率可达99%以上。