基于改进FOA的风机叶片结构损伤检测

为解决风轮叶片多损伤情况下的结构损伤识别问题,提出一种基于单元模态应变能变化率和改进果蝇优化算法的分步损伤判别方法。该方法首先采用单元模态应变能变化率对损伤进行初步判定,然后利用果蝇优化算法对损伤位置和程度进行精确识别。由于传统果蝇优化算法极易陷入局部最优问题,则对其进行了改进。结果表明:采用单元模态应变能变化率可以有效识别出可能的损伤单元,在此基础上用改进果蝇优化算法可以更精确地识别结构损伤位置和程度,同时采用改进果蝇优化算法的识别精度明显优于简单果蝇优化算法。     

悬臂梁结构损伤检测仿真研究

以悬臂梁结构为研究对象,针对户外条件下结构损伤检测过程复杂、周期长、检测效果不理想的问题,提出了模态曲率变化率法.通过大型商用有限元软件ABAQUS,建立梁结构有限元模型,基于模态曲率变化率法构建损伤指标,对梁结构进行损伤检测定位,并与模态应变能法的损伤检测效果进行了对比.结果表明:模态曲率变化率法计算过程简单,能够准确快捷地对悬臂梁结构进行损伤识别定位.     

基于模态参数及小波变换的旋转梁结构损伤识别

本文采用旋转悬臂梁模型模拟旋翼直升机桨叶结构,并对其开展损伤识别问题研究.首先,基于有限元方法,采用Hamilton变分原理,建立旋转结构的动力学模型,通过对比理论和实验的结果验证模型的正确性.其次,利用不同模态参数(位移模态、应变模态)对旋转悬臂梁结构进行损伤识别研究.最后,针对位移模态,基于小波变换的奇异性分析特性,研究通过小波系数辅助损伤识别的方法.计算结果表明,对于旋转结构,应变模态的损伤识别效果较好,而位移模态若结合小波变换的奇异性分析,同样可以实现较为准确的损伤识别效果.     

空间相机桁架结构模态相关性分析

为有效地预示空间相机桁架结构的动态特性，需要对其进行模态相关性分析，目的在于检验分析结果的有效性和准确度，发现结构中的薄弱部位，但由于桁架结构是一复杂的杆板组合结构，计算结果中存在着大量次模态，从而无法与试验结果进行对比。基于上述问题，提出一种利用模态应变能比值来定量区分的方法，从密集的计算模态群中识别出桁架结构的主模态。主模态经模态向量缩减后与试验结果进行比较，鉴定它们之间的总体相关程度，若误差超过规定的界限，则通过调整模型参数、修改模型构型来寻找可能的误差源，反复这一过程，直到有限元模型能够很好地模拟实际结构的主要动态特性为止。分析结果预示了较好的试验和计算模态相关性，验证了有限元模型的有效性，为进一步的响应分析和振动控制设计提供了依据。     

战术导弹自由飞环境与试验台环境模态一致性研究

以战术导弹试验台振动环境的约束模态与导弹真实飞行模态的差异为背景,结合模态应变能法理论,提出了以单元模态应变能和总体模态应变能为评定标准的试验最优约束模态的判别方法;通过对导弹简化模型算例地面试验约束状态和空中自由飞行状态模态一致性分析,给出了地面试验最佳约束点的选择方法;最后,考虑到瞬态响应的特殊性,对战术导弹简化模型算例自由模态和约束模态瞬态响应进行了对比分析.理论分析与仿真试验证明了该方法的有效性.     

通过应变阵列测量位移模态与曲率模态

针对模态试验中使用加速度计时附加质量大、不易安装且对于结构曲率变化不敏感等问题,提出使用应变阵列测量位移模态与曲率模态.以悬臂梁为例,通过改变应变阵列的布置方法测量梁的位移和曲率模态,并与使用加速度计的模态分析结果进行对比.实验结果表明:通过改变应变阵列布置方法,可有针对性地提取结构的位移模态与曲率模态,且模态识别效果...     

火箭结构系统纵向模态自动辨识方法

针对工程中需要从火箭结构系统的整体模态中识别纵向模态,根据模态有效质量理论,提出了一种识别火箭结构系统纵向模态的自动辨识方法.以具有集中质量系统的振动特性作为算例,通过有限元软件,建立了具有集中质量系统的梁模型,利用自动辨识的方法,自动辨识出系统的纵向模态,并与应用模态分析法所计算的系统模态信息相比较,这种自动辨识方法不仅能准确的辨识出振动系统的纵向模态,而且还具有自动高效的识别特点.为准确快速建立液体火箭POGO振动系统的动力学模型等工程系统的模型提供理论依据.     

多模态过程的全自动离线模态识别方法

多模态是复杂工业生产过程的普遍特性.不同模态具有不同的过程特性,需要建立不同的模型,因此离线建模数据的模态划分与识别是整个多模态过程建模的关键问题之一.目前,常用的聚类算法需要对其结果进行人工分析和后续处理,无法真正实现多模态过程的全自动模态识别.因此,本文提出一种全自动的多模态过程离线模态识别方法.首先通过宽度为H的大切割窗口对数据进行切割,利用改进的K-means聚类算法对窗口单元进行聚类;根据聚类结果,对稳定模态淹没现象进行处理,得到模态的初步划分结果;最终,利用小滑动窗口L,对稳定模态及过渡模态交接区域进行细划分,准确定位稳定模态与过渡模态的分割点.算法实现了多模态过程的全自动离线识别,并给出合理有效的识别结果.仿真分析表明此方法能够实现模态的自动识别,且识别结果准确.     

基于改进经验模态分解的HHT密集模态识别方法

针对传统HHT方法不能有效识别密集模态的问题,提出基于改进经验模态分解(EMD)的HHT密集模态识别方法。EMD密频信号分解能力不足是限制HHT法识别密集模态的主要原因,因此在EMD分解过程中嵌入信号调频(FM)和模态解相关操作提升其分解密频信号的能力,称改进后的方法为调频-解相关模态分解(FM-DEMD)。以FM-DEMD分解取代传统HHT法中的EMD分解,得到改进HHT模态识别方法。仿真试验证明：传统HHT法和ITD法密集模态识别失效时,改进HHT法仍能准确识别密集模态信息。     

基于结构高阶局部模态的损伤诊断研究

结构振动测试和损伤诊断中,较易得到结构的低阶模态信息,但低阶模态信息主要反映结构的整体性能,对结构局部损伤不敏感.本文主要研究框架结构高阶模态特性,并通过高阶模态来反映结构的局部特征,实现框架结构损伤诊断.研究中采用理论模态分析和实验模态分析相结合的方法.理论模态分析表明框架结构存在模态密集区且高阶模态具有局部特征.采用局部激振方法对一个钢筋混凝土框架结构模型施加激励,通过实验模态分析获取高阶局部模态信息.结果表明最大能量高阶模态可以识别框架柱的刚度变化.     

A swift technique for damage detection of determinate truss structures

In this study, a novel two-stage approach for damage detection of determinate truss structures is proposed. The method lies in the group of vibration-based methods but it just needs the first natural frequency and mode shape vector of these structures for identifying the location and severity of damage. In the first stage, the modal residual force vector for different modes of a structure is introduced and the one associated with the first mode is applied to the structure as an external nodal force vector. Then, the residual local nodal force vector can be computed for all elements of the structure. Next, the elements with non-zero residual internal force are considered as damaged elements. In the second stage, the damage severity of each damaged element is determined using a new relation which can be categorized as a force–displacement relation. To show the efficiency and simplicity of the proposed method, three truss structures including a 13-bar planar truss, a 29-bar planar truss, and a 77-bar planar truss under different damage scenarios are studied; the results of which indicate that the method is innovatively capable of suitably detecting, for determinate truss structures, not only damaged members but also their individual damage severity by carrying solely one analysis.

     

A swift technique for damage detection of determinate truss structures (2)

This paper introduces a novel and robust probable statistical approach for the applied damage detection of determinate truss structures. This technique involves two steps; the first is called most probable damaged element identification step and the second is called probable damage severity prediction step. In the first step, a new index based on modal residual forces plays a major role to independently identify damage-suspected elements for each considered mode. Then among them, the elements, the most probable to damage, are extracted. In the second step, the probable damage severity for each most probable damaged element is individually predicted using a novel statistical approach. Finally, to justify the validity and robustness of the technique, three commonly used bridge trusses including a 29-bar Pratt truss, a 29-bar Warren truss, and finally, a 37-bar K truss under different damage scenarios are thoroughly studied while their modal parameters are corrupted by noise. The obtained results indicate that the method is innovatively capable of swiftly predicting, for determinate truss structures, not only damaged elements but also their damage severities by carrying out solely few structural analyses.

     

Cyclical Parthenogenesis Algorithm for guided modal strain energy based structural damage detection

In this paper, a newly developed multi-agent meta-heuristic method, named Cyclical Parthenogenesis Algorithm (CPA), is incorporated into a guided modal strain energy based structural damage detection technique. A modal strain energy based index is used to guide the structural damage identification process, which is formulated as an inverse optimization problem. Generalized Flexibility Matrix (GFM) of the structure is used to define the objective function of the optimization problem. Three numerical examples are provided in order to examine the viability of the proposed method. The results indicate that the proposed method is capable of locating and quantifying structural damage using only the first few modes of the structure. The results are also compared with those of three other meta-heuristic algorithms in order to show the efficiency of CPA in solving the problem.     

快速独立分量分析法识别结构模态参数研究

采用快速独立分量分析(FastICA)算法,快速、准确地识别结构模态参数.该算法以模态响应之间的独立性为依据构建出目标函数,并以此目标函数为基准采用ICA算法对结构输出信号进行分离,而得到结构振型向量.进而通过单模态识别技术-希尔伯特(Hilbert)变换,识别出结构的频率和阻尼比.最后通过白噪声激励下六层框架结构的模态参数识别,验证了快速独立分量分析算法识别结构模态参数的可行性和鲁棒性.     

Improved subspace modal identification of industrial robots

Industrial robots have become key components for manufacturing automations due to their larger workspaces and flexibility. However, low stiffness and high compliance of industrial robots may inevitably lead to vibration by self-excitation or periodic force dependent on workspace configuration. Therefore, the knowledge of the robot's modal properties should be accurately required to enhance the operation accuracy of industrial robots. To improve the identification accuracy of experimental modal parameters of field industrial robots, an improved subspace identification method is proposed to perform nonlinear iterative optimization for updating the state parameters of industrial robots. Experimental response measurement of a six-degrees-of-freedom industrial robot is carried out to obtain modal parameters under various poses. The identification results of the improved subspace modal method are preferable to that of the traditional method. Moreover, the reconstructed three-dimension working frequency space is presented to exactly characterize experimental modal frequencies throughout its workspace. The proposed method effectively improves the identification accuracy of modal parameters when compared with the traditional algorithms and the influence of robots' pose change on modal parameters is also investigated by experimental modal measurements.     

基于模态瞬态法的发动机罩焊点疲劳优化

针对某车型整车耐久路试过程中发动机罩铰链加强板焊点出现开裂的问题,采用模态瞬态法对发动机罩焊点进行疲劳分析。根据发动机罩模态应变能分布情况优化铰链加强板结构和焊点分布,试验车整改后在整车耐久路试中发动机罩焊点未再出现开裂现象。发动机罩铰链加强板焊点开裂是振动疲劳问题,采用基于惯性释放的准静态法计算疲劳损伤不能预测焊点开裂问题,采用模态瞬态法疲劳计算方法才能更好地预测发动机罩焊点疲劳损伤。从模态应变能角度对结构振动疲劳开裂问题进行优化能明显提高优化效率。     

基于等效模态阻尼的复合隔振系统振动计算方法

基于线性黏弹性假设,将应变能阻尼理论推广到复合隔振系统的等效模态阻尼计算中,运用Python和Abaqus编制相应的计算程序,该程序可考虑材料阻尼的频变特性。以多种材料组成的船舶双层复合隔振系统为算例,计算其等效模态阻尼和隔振器等效阻尼系数。分别采用直接积分法和模态叠加法计算系统振动响应,对比设备、筏架、船底壳的振动加速度响应,验证基于等效模态阻尼的模态叠加法的准确性。结果表明,该方法可以准确计算复杂组合模型的模态阻尼,算例的振动响应计算结果一致性较好,用模态叠加法可以大幅提高复合隔振系统稳态振动响应的计算效率。     

基于Abaqus的模态分析方法对比及验证

模态分析是目前研究结构动力学特性的重要方法,已经成为解决现代复杂结构动态特性设计的重要手段,模态分析对计算模型有效性验证和结构优化都能起到指导作用.在对比分析现有模态分析方法基础上,利用Abaqus对Lanczos方法下2种单元类型模型进行对比分析,并与理论值进行比较.     

基于压缩采样和模态分析的冲击载荷反演研究

近年来,许多学者针对大型飞行器结构的冲击载荷识别进行研究,以期提高这些结构的安全性、降低维护费用、延长使用寿命.在大型结构健康监测中,如何快速、准确地获得冲击力是一个值得深入研究的问题.提出了基于数据的模态分析方法,取代基于有限元分析的模态分析方法,解决传统载荷反演需要依赖结构力学模型的问题;并引入压缩采样理论,基于压缩采样理论提出了一种冲击载荷识别方法,其中包含了稀疏模型,即采样矩阵,还包含重构优化模型;该方法可以解决存储及传输的响应数据过于庞大的问题.最后,用一块大型航空铝板仿真实验来举例说明该冲击力识别方法,结果显示,该方法能够快速、准确地识别出作用在大型结构上的冲击力.