基于广义柔度和附加质量的结构损伤识别研究

通过在结构的某些部位附加已知的集中质量块,测量附加质量后结构振动的低阶模态,把这些新的模态参数及原结构的模态参数联合起来,通过广义柔度灵敏度来建立损伤识别方程求解损伤参数。以一个桁架结构为例对所提的方法进行验证。研究结果表明,仅需要测量原结构和附加质量后结构的第一阶模态信息就可以比较准确地识别出结构的损伤,说明了所提方法的可行性,为解决大型结构的损伤识别问题提供了一条可供参考的途径。     

结构损伤检测的一种改进附加质量方法

提出一种改进的附加质量方法用于结构的损伤检测中。通过在结构的某些部位处附加已知的集中质量块,测量得到附加质量系统的低阶模态,将这些新的模态及原结构的模态联合起来,通过频率灵敏度和柔度灵敏度建立损伤识别方程求解损伤参数。以一个二层的框架结构为算例,对所提的改进附加质量方法进行验证。研究结果表明,仅需要测量原结构和附加质量后结构的少数低阶模态信息,即可以比较准确地检测出结构的损伤,说明附加质量方法的可行性。     

一种基于模型修改的结构多点损伤识别方法

可用于结构损伤识别的方法很多。一般来讲正向方法直接利用结构模态参数的变化，逆向方法则利用模态参数变化反演结构物理参数变化，还有些方法利用了神经网络和模式识别技术。文中利用模型修改的思想，通过逆向方法计算结构单元刚度变化系数来对结构的多点损伤进行识别。以一个七自由度弹簧阻尼质量系统作为研究对象，用数值模拟方法及特征系统实现算法计算系统的模态参数，并用这些模态参数验证所提出方法的可行性，结果表明该方法对多点损伤的识别是简单而可行的。     

某水下航行器电机支架的动力学分析

振动噪声是水下航行器的重要指标,水下航行器的电机支架是振动传递的关键,因此以某水下航行器电机支架为研究对象,采用CAD软件Sol-id Edge建模,用有限元软件ANSYS Workbench对其进行动力学分析,包括模态分析和谐响应分析。通过有限元计算得到电机支架的固有频率和对应的振型,进而计算出结构的频率响应曲线,分析峰值频率对应的应力与变形,找出电机机架的共振频率,最后评估水下航行器电机支架的动态性能,为支架进一步结构设计提供了理论依据。     

铁道车辆物理参数识别方法研究

针对铁道车辆物理参数识别问题,首先通过状态空间理论和模态空间理论获得了车辆系统状态矩阵,接着分别提出了附加质量法和比例关系法两种铁道车辆物理参数识别方法。附加质量法可识别车辆全部物理参数,但需要将特定的质量附加到车辆系统中。比例关系法无需附加质量,以构架质量参数已知为前提条件来对车辆其余物理参数进行识别。设计了用于物理参数识别的车辆定向激励工况,并通过仿真试验对两种物理参数识别方法进行了验证及对比分析。结果表明,采用附加质量法进行车辆物理参数识别时,附加质量大小选取为车辆系统质量的3%识别精度最高;附加质量法和比例关系法在识别精度和测试实施难度方面各有优缺点,因此,在实际车辆物理参数识别中,可根据现场情况,合理选择识别方法。     

推力脉动引起的水下高速航行器振动响应研究

尾部推力脉动会引起水下高速航行器的冲击和振动,直接影响航行器壳体强度和航行稳定性。文中研究了推力脉动对水下高速航行器壳体振动的影响。以ANSYS有限元分析软件为平台,建立壳体3D有限元模型,进行了壳体整体模态分析和轴向推力脉动振动响应分析。计算结果表明尾部推力脉动会引起航行器壳体沿轴向的伸缩振动,壳体上位置离激振力越远,受到的径向振幅越大。     

热动力系统性能参数预测与理论分析

为了增加航行器的航程和优化航行器各种仪器的工作条件 ,航行器的航速应不断发生变化 ,这就需要解决航行器在慢速航行时 ,热动力系统的性能和结构参数的配置问题。本文以热动力系统总体参数为出发点 ,对热动力系统中的发动机、燃烧室及燃料供应分系统的参数配置进行了预测和理论分析。本文可为水下航行器的航速设计及计算方法提供参考。     

无人水下航行器壳体流体动力的计算

采用计算流体力学方法对无人水下航行器壳体流体动力特性进行数值模拟与计算。计算结果与风洞试验结果对比表明,该方法对无人水下航行器壳体流体动力特性的预测精度较高。该研究成果对无人水下航行器的外形设计具有缩短周期,节约费用和降低风险的效果。     

水下航行器尾轴密封结构的研究

计算了橡胶O形圈和机械密封结构在水下航行器尾轴密封中的摩擦功率损耗。结果表明，使用机械密封的摩擦功耗比橡胶O形圈的少，采用机械密封可以提高水下航行器的航程。     

动态载荷时域识别方法的研究

振动系统模态参数的获取是时域荷识别方法的关键。文中提出了模态系数的优化识别算法，系统介绍了时域法识别动态载荷的各个过程，包括模态参数的识别和动态载荷的识别。仿真算例表明，该方法精度较高，对噪声不敏感，可以用于实际载荷的识别。     

Numerical study on the hydrodynamic control derivatives of a high-speed underwater vehicle with X-stern configuration

A numerical study using a computational fluid dynamics approach is conducted on the control effectiveness of a high-speed underwater vehicle with an X-stern configuration. The calculation method is verified by comparing its results with the calculation results and measurements of control derivatives of an underwater vehicle with a cruciform stern configuration. The results of the study show that the control effectiveness of a high-speed underwater vehicle is improved by about 40% in terms of control derivatives, when the cruciform stern configuration is replaced with an X-stern configuration.     

Physical parameter identification method based on modal analysis for two-axis on-road vehicles: Theory and simulation

Physical parameters are very important for vehicle dynamic modeling and analysis. However, most of physical parameter identification methods are assuming some physical parameters of vehicle are known, and the other unknown parameters can be identified. In order to identify physical parameters of vehicle in the case that all physical parameters are unknown, a methodology based on the State Variable Method(SVM) for physical parameter identification of two-axis on-road vehicle is presented. The modal parameters of the vehicle are identified by the SVM, furthermore, the physical parameters of the vehicle are estimated by least squares method. In numerical simulations, physical parameters of Ford Granada are chosen as parameters of vehicle model, and half-sine bump function is chosen to simulate tire stimulated by impulse excitation. The first numerical simulation shows that the present method can identify all of the physical parameters and the largest absolute value of percentage error of the identified physical parameter is 0.205%;and the effect of the errors of additional mass, structural parameter and measurement noise are discussed in the following simulations, the results shows that when signal contains 30 dB noise, the largest absolute value of percentage error of the identification is 3.78%. These simulations verify that the presented method is effective and accurate for physical parameter identification of two-axis on-road vehicles. The proposed methodology can identify all physical parameters of 7-DOF vehicle model by using free-decay responses of vehicle without need to assume some physical parameters are known.     

舵板张开过程的数值仿真与试验研究

采用流固耦合数值计算方法和动网格技术,对一种水下航行体舵板在张开过程中的速度、载荷以及动态响应变化规律开展了研究,对影响舵板张开的尾部高温燃气、水下航行体运动速度等因素进行了分析。在此基础上,根据速度等效原则设计了验证试验方案,试验中获取了舵板张开过程的位移-时间曲线、应力-时间曲线以及舵板张开时间与出水速度的关系。仿真计算结果与试验结果对比表明:该计算结果可为水下航行体的水弹道分析、舵板结构设计和材料选择提供依据。     

脱泡器双螺旋叶片结构动力特性分析

搅拌器的双螺旋叶片工作在高粘度胶液中.文中分别推导了叶片在空气中的动力特性方程及在胶液中的流固耦合方程,并通过ANSYS对其动力特性进行了仿真计算,得到了搅拌叶片前十阶频率及其振型.其中在胶液中进行动力特性分析时运用了附加质量法,通过表面效应单元传递了流体对叶片的反作用力.结果表明,叶片在胶液中的固有频率比空气中有所降...     

考虑转向架影响的重载货车车厢模态特性

为深入研究转向架对重载货车动力学特性的影响,以某空车工况的40t轴重矿石车为研究对象,在实车装配模型的基础上建立了整车及车厢的力学仿真模型,并应用有限元法对二者进行了模态分析。对实际车辆进行了模态实验研究,通过计算结果及实验结果的对比,从刚体振型及弹性体振型两个方面考察了转向架对重载货车车厢模态特性的影响。研究表明,转向架的质量、刚度及边界条件均会对模态计算结果产生影响,整车模型能更精确地描述实车的模态特性。     

Operational mode-shape normalisation with a structural modification for small and light structures

When dealing with small and light structures, difficulties occur when measuring the modal parameters. The resonant frequencies are usually relatively high and therefore a wide frequency range is needed for the measurement. Furthermore, the mass that is added to the structure by the sensors causes structural modifications. To overcome these difficulties, an improved method using an operational modal analysis instead of an experimental modal analysis is proposed in this study. It is derived from the sensitivity-based operational mode-shape normalisation with a consideration of the mode-shape variation. The measurement of the excitation force is not needed, because the operational modal analysis is used and only two simultaneous response measurements at an unknown excitation are required. The proposed method includes the cancellation of the added mass, resulting in mode shapes and resonant frequencies of the unmodified structure. The numerical and experimental results on small and light structures are compared with the results of the experimental modal analysis. The comparison shows that the proposed approach allows measurements over a wide frequency range and increases the accuracy of the results compared to the sensitivity-based operational mode-shape normalisation and also compared to the particular experimental modal analysis method that was used in this study. The advantages of the proposed method can be seen whenever the mass that is added to the structure by the accelerometer is not negligible and therefore a variation of the mode shapes occurs.     

Numerical study on control derivatives of a high-speed underwater vehicle

This paper presents a numerical study on control effectiveness of a high-speed underwater vehicle with cruciform stern configuration using a computational fluid dynamics approach. The calculation of the control derivatives of the underwater vehicle is validated by comparison with the experimental results of towing tank tests. The screw propeller of the vehicle is modeled as a momentum source and its influence on the computational results is examined. The numerical results show that the force derivatives of the vehicle are over-predicted by about 5% and the moment derivatives of the vehicle are over-predicted by about 10%.     

基于ANSYS Workbench水下航行器壳体的有限元分析

通过几何制图软件,建立了某水下航行器壳体的有限元数值模型;在有限元分析软件中,对该模型进行了应力及关键部位的模态分析;确定了该水下航行器壳体结构的最大应力和固有频率等相关数值信息,避免结构设计缺陷导致的应力集中及共振问题。缩短了研发时间,减少了设计人员的工作量,降低了研发成本;同时,给壳体结构的改进指明了方向,为实体的顺利生产提供了可靠的参考依据。     

基于回归模型的SDBD-PA击穿特性试验研究

近年来,表面介质阻挡放电等离子体激励器（Surface dielectric barrier discharge plasma actuator,SDBD-PA）已经成为流动控制领域的研究热点。为研究SDBD-PA的击穿特性,为SDBD-PA相关研究的参数区间选取提供参考,首先采用控制变量法研究各激励器参数对SDBD-PA击穿电压和放电稳定性的影响,然后选取对击穿电压有影响的激励器参数,基于DOE方法进行试验,使用Isight软件建立二次回归模型并分析激励器参数对击穿电压的影响。研究结果表明,对SDBD-PA击穿电压和放电稳定性有影响的参数包括频率f、电极间隙d₁和激励器长度L;拟合所得三元二次回归模型经验证具有良好的精确度,可作为SDBD-PA击穿电压的预测模型;对SDBD-PA击穿电压影响最大的参数是f,其次为L和d₁;f和L对击穿电压的影响为负效应,d₁对击穿电压的影响为正效应;d₁和f之间以及f和L之间的交互作用对击穿电压也有很大影响,d₁和L之间的交互作用对击穿电压的影响非常小。