基于齿轮箱结构的试验模态测试研究

现代机器多要求高速、高效、低耗能、轻型、低噪声和性能可靠.这些都离不开动态测试与分析,因而模态测试技术得到迅速发展和广泛应用.目前的发展趋势是把有限元方法和试验模态分析技术结合起来.     

舰船模型模态试验的研究

介绍模态分析基础理论知识与模态测试技术,然后重点对模型的模态试验作了详细叙述,并分析试验结果。     

数控机床振动故障诊断软件的开发

针对数控机床振动信号的振动机理和振动特点,结合故障诊断技术和模态分析技术,以LabVIEW软件为平台,开发了一套向导式振动故障诊断系统。该系统可以实现8通道高速数据采集、数据分析、数据保存,数据回放、模态分析和故障诊断功能,详细的介绍了软件设计流程和关键部分设计思路,给出了部分前面板设计图。并对某公司生产的数控机床进行了振动信号采集、模态测试和故障分析,试验证明,软件的各项功能很好地满足了振动监测、模态测试和故障诊断的要求,进而验证了该软件系统的可靠性和实用性。     

振动模态测试及仿真分析的研究与应用

对振动模态测试和仿真原理进行剖析,分析两种方法对结构模态研究的优缺项点。并对压板进行有限元模态分析及试验测试,对比分析上述两种方法所得模态频率结果的最大误差为4.19%,属于可接受范围。通过该研究,探索振动模态测试和仿真分析方法,使测试结果与有限元仿真结果相互验证、融合,以提高模态分析的精度。     

一种计及滑块裙部变形的滚珠直线导轨副模态分析方法

基于计及滚珠直线导轨副滑块裙部变形的刚度模型,提出了一种滚珠直线导轨副的有限元模态分析方法,建立了一种滚珠直线导轨副的三维有限元模型并进行了有限元模态分析,求得了滚珠直线导轨副的模态频率及模态振型。利用实验模态分析技术,对滚珠直线导轨副进行了模态测试,测得了滚珠直线导轨副的模态。测试结果验证了有限元建模与分析方法的有效性。     

核电站环行起重机模态测试和抗震分析

文中对模态分析、模态测试的原理进行了剖析,对模态参数和模态叠加法在结构抗震分析时的应用进行了梳理,并针对小型简支梁结构进行了验证性测试。结果表明：模态测试和有限元计算得到的模态参数比较匹配,各阶固有频率平均相差4%。另外,通过对CAP1400核电站环行起重机桥架进行模态测试方法设计以及现场模态测试,得出桥架的前3阶固有频率和阻尼比。测试结果与有限元仿真比对的结果表明,前3阶固有频率相差不大,仿真模型具有一定的可靠性。     

基于贝叶斯运行模态分析法的砂轮架动态特性分析

为了研究砂轮架的固有模态和在工作环境中的谐波模态,运用贝叶斯理论和运行模态分析相结合的模态参数识别技术--分步测试的贝叶斯运行模态分析法对环境状态下的砂轮架进行模态识别,获得了结构的动态特性,包括固有频率、振型以及阻尼特性等,并对外激励和预测误差水平以及信噪比进行了评估;将该模态识别结果与传统试验模态分析结果进行对比,验证了贝叶斯运行模态分析法的应用可行性;进一步在工作环境下对砂轮架进行了振动测试,对比开机前的模态识别结果和开机后砂轮架的功率谱密度图,成功地区分出砂轮架的固有模态和实际工作环境中由结构周期激励引起的谐波模态。     

挖掘机齿轮箱动态特性的实验与仿真分析

齿轮箱的动态特性对变速器及整机的振动性能影响极大。结合有限元及测试技术对XG958H型号的挖掘机齿轮箱进行自由模态分析和测试,获得了箱体的模态参数;应用ANSYS Workbench分析软件对齿轮箱进行模态仿真分析,并同时基于LMS测试分析系统,利用最小二乘复频域法拾取齿轮箱各阶段模态参数。结果表明,两种方法得出的结果基本一致,最大误差为7.54%,验证了LMS实验方法与ANSYS Workbench模拟方案的可靠性,为避免齿轮箱工作时可能产生的共振频率提供参考。     

薄膜天线结构在真空中的模态测试方法

由于薄膜结构为轻质柔性结构，空气对其模态分析结果具有不可忽略的影响，因此在真空环境中开展模态试验是十分必要的。以平面薄膜天线结构为研究对象，设计并搭建了一套适用于真空环境下的模态测试系统，完成了多种工况下的模态测试，并获得了有效测试数据。通过对数据进行处理和对比分析，不仅验证了该测试系统的有效性和可行性，而且还获得了空气对模态测试结果产生的具体影响，得到了有用结论。该试验研究内容为薄膜天线的模态特性研究和设计改进奠定了坚实的技术基础，具有十分重要的工程意义。     

面向机械参量集成测试的虚拟仪器

针对传统机械量测试中存在的问题,以DSP为核心,利用虚拟仪器开发软件LabVIEW构建了基于VI技术的虚拟仪器测试系统,包括数据采集、显示、时域分析、频域分析和数据存储等功能.利用虚拟仪器软件控制数据采集卡采集数据,用Star System专业软件进行数据和机械结构模态分析,完成机械测试过程.实验结果表明:该方法使模态分析过程得到了简化,可降低设备成本,为机械工程领域的信号测试与分析提供一种实用手段.     

Modal parameter identification in atmospheric turbulence excitation flutter test based on Hilbert-Huang transform

In flutter tests, particularly in wind tunnel experiments, the aircraft model is generally excited by atmospheric turbulence, which increases the difficulty in precisely identifying the modal parameters. To estimate the modal parameters under turbulence excitation for flutter boundary prediction, a technique was developed and evaluated depending on the Hilbert-Huang transform in this paper. The results of simulated flutter cases show that the developed technique can identify modal frequencies more precisely than the modal damping ratio, while the estimation of the modal damping ratio is quite good. Finally, in a wind tunnel flutter test, good flutter boundaries were predicted in advance by using the modal parameters identified from the turbulence response at low airspeeds.

     

基于动特性分析的精密仪表转子-框架结构优化设计

为提高精密仪表的动态稳定性，提出一种基于结构特性分析的综合优化设计方法。该法将有限元计算和模态试验相结合，利用有限元法分析最初的设计结构动态特性，然后对该结构进行试验模态分析，从而检验有限元分析方法的可信度，利用经过验证的简化模型和计算分析，分析结构参数改变时对系统动特性的影响，进而实现结构的优化设计，从转子-框架结构的优化过程可以看出，该方法在保证可靠性的同时大大降低了成本，并且提高了效率，可广泛应用于工程设计中。     

某车架结构基于灵敏度分析的优化设计

建立了某自卸车车架有限元模型,通过模态试验和模态有限元分析得出了车架固有频率,并且验证了该模型的准确性和合理性。依据车架结构的灵敏度分析结果来选择设计变量,在保证车架低阶模态频率和强度的前提下,以车架轻量化为目标优化车架构件厚度,实现了车架质量8.0%的降低幅度;在控制车架质量和强度的条件下,以提高车架低阶模态频率为目标,实现了车架结构的低阶模态频率和动态性能的提高。     

Output-only modal analysis of wind turbine tower based on vibration response under emergency stop

The identification technique of output-only modal parameters is proposed for the large wind turbine tower under emergency stop. Compared with the response of regular operating conditions, the immediate tower structural response under emergency stop much more resembles a state of free vibration, which is more appropriate for the modal identification of the wind turbine tower. The vibration response is measured in the nacelle, which is easy to perform in the field modal test. The variational mode decomposition (VMD) is applied to decompose the vibration response into several band-limited intrinsic mode functions. The free responses of decomposed functions are extracted by applying the random decrement technique (RDT). Finally, the modal damping ratio and natural frequency are identified from each free modal response by using the Hilbert transform method. Simulations and a 1.5 MW wind turbine field modal test results verify the effectiveness of the proposed identification method. The main modal parameters of wind turbine, including weak modes, are effectively extracted by using output-only vibration responses under emergency stop. The modal parameter identification method is provided for the large wind turbine structure under the engineering condition.     

支撑条件对钢轨模态参数影响研究

钢轨的振动形态直接影响着铁路轮轨的接触状态,不同的支撑条件对钢轨的振动有着较大的影响.本文应用模态分析和有限元理论研究了钢轨不同支撑条件对钢轨固有频率和振型的影响.应用环境激励下模态参数识别方法对钢轨在不同支撑条件下的模态参数进行了识别.针对四种支撑方式,分别得到了模态参数,通过理论和试验分析表明,不同的支撑方式对轨道模态参数有较大影响.这一结论为合理铺设轨道提供依据.     

Measurement and correlation of high frequency behaviors of a very flexible beam undergoing large deformation

A correlation method of high frequency behaviors of a very flexible beam undergoing large displacement is presented. The suggested method based on the experimental modal analysis leads to more accurate correlation results because it directly uses the modal parameters of each mode achieved from experiment. First, the modal testing and the parameter identification method are suggested for flexible multibody dynamics. Due to the flexibility of a very thin beam, traditional testing methods such as impact hammer or contact type accelerometer are not working well. The suggested measurement with high speed camera, even though the test beam is very flexible, is working well. Using measurements with a high speed camera, modal properties until the 5th mode are measured. And After measuring each damping ratio until the 5th mode, a generic damping model is constructed using inverse modal transformation technique. It’s very interesting that the modal transformation technique can be also applied even in the ANCF simulation which uses the global displacement and finite slope as the nodal coordinates. The results of experiment and simulation are compared until the 5th mode frequency, respectively, by using ANCF forced vibration analysis. Through comparison between numerical simulation and experiment, this study showed that the proposed generic damping matrix, modal testing and parameter identification method is very proper in flexible multibody dynamic problems undergoing large deformation.     

车身结构振动与车内噪声声场耦合分析与控制

车内低频噪声直接影响其乘坐舒适性,应用有限元和模态分析技术对汽车车身结构振动和车内噪声耦合问题进行了研究,利用有限元法找出车身结构动态特性和空腔声学特性,与试验模态结果进行比较,两者在低频范围内基本一致。在此基础上,应用声—固耦合理论对该车身结构振动与车内噪声耦合进行了研究,得出的结论为降低由结构振动引起的车内低频噪声提供了理论依据。     

基于模态理论的白车身静刚度计算方法

以线性系统的模态理论为基础,将简单矩形框架的弹性体模态与静刚度之间的关联性推广到白车身,推导出了具体的数学表达式,再以此为依据,通过有限元分析直接提取各阶弹性体模态参数,从而获取车身静刚度,改变了以往依靠柔度矩阵和大型试验来计算静刚度的方法。研究结果表明,模态理论方法和传统静力学方法所得到的静刚度相差在10%以内,说明白车身的整体静态柔度可以用模态柔度贡献量之和表达,且这种计算方法具有较高精度,能为低阶模态和刚度性能的目标设定提供参考。同时,各阶模态的柔度贡献量的大小可以作为低阶模态识别的重要依据。最后将有限元计算结果与白车身静刚度试验结果作对比,其误差控制在8%以内,其中由模态方法计算的扭转刚度误差低于3%,因此说明此次有限元分析是可靠的。     

基于环境激励的大跨度钢桥模态试验研究

模态试验是桥梁结构试验考核的重要内容之一,试验获得的模态参数对验证结构设计、建立结构的动力学模型以及使用状态的评估均具有重要意义.传统的模态试验方法是采用人工激励法进行激振,但对于大跨度钢桥无论是实施人工激励还是测试外部激励都是困难的.为此,采用基于环境激励的谱分析方法对某型大跨度钢桥进行了模态测试与分析,并对测试设备、传感器、分析软件作必要的配置与完善,给出了某型大跨度钢桥空载状态下的阵型及相应的固有频率,为同类装备的模态试验及振动特性分析提供了参考.     

An experimental investigation on the effects of exponential window and impact force level on harmonic reduction in impact-synchronous modal analysis

A novel method called Impact-synchronous modal analysis (ISMA) was proposed previously which allows modal testing to be performed during operation. This technique focuses on signal processing of the upstream data to provide cleaner Frequency response function (FRF) estimation prior to modal extraction. Two important parameters, i.e., windowing function and impact force level were identified and their effect on the effectiveness of this technique were experimentally investigated. When performing modal testing during running condition, the cyclic loads signals are dominant in the measured response for the entire time history. Exponential window is effectively in minimizing leakage and attenuating signals of non-synchronous running speed, its harmonics and noises to zero at the end of each time record window block. Besides, with the information of the calculated cyclic force, suitable amount of impact force to be applied on the system could be decided prior to performing ISMA. Maximum allowable impact force could be determined from nonlinearity test using coherence function. By applying higher impact forces than the cyclic loads along with an ideal decay rate in ISMA, harmonic reduction is significantly achieved in FRF estimation. Subsequently, the dynamic characteristics of the system are successfully extracted from a cleaner FRF and the results obtained are comparable with Experimental modal analysis (EMA).