基于模态振型的自由阻尼层厚度分布优化

阻尼材料的敷设位置和敷设厚度分布对结构减振效果有较大影响,针对阻尼材料敷设厚度分布优化问题,提出了一种基于模态振型的阻尼层敷设厚度分布优化方法。该方法用一组模态振型线性组合来定义阻尼层厚度分布函数,将模态参与因子作为设计变量来优化阻尼层厚度分布。研究了给定阻尼材料下自由阻尼层厚度分布优化问题,数值算例表明,与均匀敷设阻尼相比,阻尼层敷设厚度分布优化后的结构能更有效地抑制结构振动,提高阻尼材料的利用率。     

基于边光滑有限元法的二维复合弹性空腔声振特性分析

基于弹性梁的弯曲理论和黏弹层线粘弹性理论及黏弹层的耗散性能,将敷设黏弹层和约束层的二维复合弹性空腔的结构域等效成被动约束阻尼梁结构,并考虑结构域与声腔域的声振耦合作用,建立了二维复合弹性空腔的边光滑有限元耦合动力学控制方程。以二维全敷设复合矩形空腔模型为数值算例,通过与标准有限元法的比较,证明了边光滑有限元法具有更高的精确性和收敛性。最后,把边光滑有限元法应用于敷设有CLD结构某汽车耦合模型,得到了黏弹层和约束层厚度参数跟耦合系统减振性能的正相关结论。     

约束阻尼板增材式拓扑渐进法减振动力学优化

研究阻尼结构的阻尼材料最优布局问题。基于虚功原理,构建约束阻尼板振动微分方程,从约束阻尼板若干基本假设出发并根据阻尼板自由振动微分方程,推导了结构模态阻尼比表达式。建立了以阻尼单元相对密度为拓扑设计变量,模态阻尼比最大为优化目标,阻尼材料用量为约束的阻尼结构拓扑优化数学模型。以阻尼单元模态阻尼比敏度为寻优方向的依据,采用增材式渐进法(AESO)求解优化模型,并依据拓扑优化准则在结构上不断敷设阻尼材料。编程实现了AESO算法,仿真计算表明:采用AESO优化时,阻尼材料主要敷设于结构的模态应变较大位置,且不会产生棋盘格现象,并且优化后的结构一阶模态阻尼比较优化前可增加83.6%,而常规渐进法带来的增幅仅72.13%。为进一步验证优化效果,还对结构进行了谐响应分析,结果表明采用增材式渐进法优化时,结构可获得更佳减振效果。     

声腔-弹性板结构在不同激励下声辐射特性研究

以声腔-弹性板声振耦合模型为研究对象,对比分析该模型在点力激励和点声源激励下,激励位置、声腔厚度以及弹性边界等对弹性板声辐射功率、表面振速和腔内声压的影响及两种情况下的区别。弹性板的振动位移函数通过谱几何方法得到,并采用Hamliton原理,充分考虑了板的振动与板两侧声场之间的耦合。利用Rayleigh积分,可计算出弹性板的声辐射特性参数。结果表明,在简支约束情况时,点力和点声源两种激励下,激励位置、声腔厚度和弹性边界对板的声辐射功率、表面振速和腔内声压有不同的变化。在薄声腔时,点力激励下,声腔个别模态对板有明显影响。点声源激励下,模型耦合作用明显,弹性板的声辐射功率、表面振速和腔内声压主要受到耦合模态的影响,且点声源的耦合作用明显强于点力作用。相较于扭转刚度,直线刚度对声辐射的影响更大。     

粘弹性阻尼安装架结构设计及减振效能分析

粘弹性阻尼材料的最大优点是可以在很宽的频域和温域内对振动进行抑制,特别适用于机载电子设备结构减振问题.文中阐述了在某机载电子设备安装架上敷设粘弹性阻尼材料的方法和典型工艺,并利用有限元仿真方法对安装架敷设阻尼层前后的减振效能进行了对比,结果表明敷设阻尼层后的安装架有更好的减振效能.     

阻尼降噪车轮的有限元分析与研究

采用阻尼技术,以车轮表面贴阻尼板的方式设计降噪车轮.利用有限元分析方法,对贴有降噪阻尼板的降噪车轮和无处理车轮进行模态计算、谐响应计算,并进行相应的试验测试.模态计算结果显示,在高频段阻尼车轮减振降噪效果明显优于无处理车轮.谐响应计算表明,在相同激励力作用下,与无处理车轮相比,阻尼降噪车轮在较大频率范围内同一节点的动力响应有很大程度的降低.试验测试证明在车辆速度较低时,两者产生的噪声水平相当;但是,在车辆速度较高时,阻尼降噪车轮具有明显的降噪效果.因此采用在结构表面上敷设一层约束层,约束层上粘贴薄层的黏弹性材料,然后在最上面增加一层约束层的方式设计车轮阻尼装置,能起到较好的减振降噪效果.     

基于板件贡献分析的装载机驾驶室低噪声设计

分别建立某装载机驾驶室及室内声腔有限元模型,通过单点输入多点输出(single input and multiple output,简称SIMO)法模态试验验证了声振耦合模型的准确性,测取悬置点激励进行频率响应分析及室内噪声预测。对驾驶室进行声学灵敏度分析,采用声传递向量法对驾驶室进行声学板件贡献度分析并对关键板件进行形貌优化,同时添加橡胶阻尼材料抑制壁板振动,进行二次声压虚拟预测。结果表明,声学灵敏度分析可得到多阶关键声振耦合频率,声传递向量法板件贡献度分析能准确定位产生噪声峰值的关键板件,形貌优化及添加阻尼材料的方案降噪效果显著,室内总声压级降低了4.43dB。此方案系统地为低噪声车身设计提供了技术路线,减少了传统方案的主观性和重复性,缩短了研发周期,降低了研发成本。     

周期开孔阻尼夹层板结构声辐射特性研究

基于阻尼减振原理,并引用周期性边界条件,从抑制声桥振动能量传递入手,建立了双层板中间夹开孔阻尼的模型;考虑了阻尼材料的频变特性,通过有限元和边界元的数值算法计算辐射声功率,分析了周期性开孔阻尼夹层板结构的声辐射特性。数值计算结果表明在中低频频段内,双层板结构中间敷设周期开孔阻尼对比全敷阻尼抑制双层板结构声辐射能力在某些频段更优,且能达到减少阻尼材料的使用,优化整体结构的重量;分析了周期性开孔阻尼夹层板结构开孔率和周期数对抑制双层板结构声辐射的影响,找到了抑制夹层板声辐射的最优的开孔率和周期数,并对仿真结果进行了相应的实验验证。     

含弹性约束复合阻尼板的振动机理与特性

针对汽车车身减振降噪需求,开发新型复合黏弹性阻尼材料。基于经典的自由阻尼和约束阻尼耗能原理,提出了一种含弹性约束的具有剪切和弯曲复合耗能机制的复合阻尼层结构。基于层间位移连续关系和薄板理论建立了阻尼复合板的位移方程和应变能能量方程,针对局部阻尼敷设及四边简支边界条件,结合假设模态法,推导出了复合阻尼板的运动微分方程、振动频率特征值方程等,求解得到了复合阻尼板的固有频率及损耗因子。复合阻尼层可用于研究单相材料不同参数特性及多相材料性能对比,且随着弹性层的上移,减振性能越好。复合耗能机理公式的推导,也为其在汽车上应用提供理论依据。     

含弹性约束复合阻尼板的振动机理与特性

针对汽车车身减振降噪需求，开发新型复合黏弹性阻尼材料。基于经典的自由阻尼和约束阻尼耗能原理，提出了一种含弹性约束的具有剪切和弯曲复合耗能机制的复合阻尼层结构。基于层间位移连续关系和薄板理论建立了阻尼复合板的位移方程和应变能能量方程，针对局部阻尼敷设及四边简支边界条件，结合假设模态法，推导出了复合阻尼板的运动微分方程、振动频率特征值方程等，求解得到了复合阻尼板的固有频率及损耗因子。复合阻尼层可用于研究单相材料不同参数特性及多相材料性能对比，且随着弹性层的上移，减振性能越好。复合耗能机理公式的推导，也为其在汽车上应用提供理论依据。     

燃烧室结构-声耦合特性研究

声振耦合影响燃烧室燃烧稳定性,加剧火焰筒薄壁结构疲劳破坏,声振耦合特性研究对燃烧室燃烧稳定性设计与结构抗疲劳设计非常必要。利用有限元软件建立燃烧室结构-声三维模型,进行燃烧室封闭结构声振耦合特性研究,计算出结构的固有频率和模态振型。通过试验,测量燃烧室声振传递函数,得到燃烧室结构声振耦合固有频率和模态振型。研究表明,声场相当于给结构增加了附加质量,降低了结构固有频率,并产生了特殊的耦合频率。试验验证了有限元计算结果的正确性,从而为燃烧室薄壁结构设计提供了参考。     

An acoustic–structural interaction modelling for the evaluation of a gearbox-radiated noise

Gearbox power transmissions are widely used in the automotive industry. They have a complex vibro-acoustic behaviour that is influenced by the various acoustic–structural interaction mechanisms. This paper concentrates on modelling these systems using a three-dimensional finite-element (FE) approach for the structure combined with a Rayleigh integral (RI) method for the acoustic radiation process. A modal analysis method is used to evaluate the elasto-acoustic modal characteristics for the coupled system. Effect of the fluid inside the gearbox on the vibration response is discussed. The combined use of this FE/RI model enables evaluation of the acoustic response. A case study of a simplified gearbox internally excited with gear mesh stiffness fluctuation is presented. Vibratory analysis allows concluding that the vibro-acoustic coupling between elastic housing, air-cavity and free acoustic field have not to be neglected.     

Viscothermal fluid effects on vibro-acoustic behaviour of double elastic panels

This paper deals with the vibro-acoustic behaviour of two vibrating plates coupled to a viscothermal fluid cavity. The acousto-elastic model is established in dimensionless appropriate form including the effects of viscosity and thermal conductivity of fluid and taking into account the fluid–structure interaction. The finite element method is used for the discretization of the functional of energy, which gives after minimization a symmetrical coupled matrix system in which the acoustic matrices are frequency dependent. For this purpose, an iterative procedure is derived to determine the eigenmodes of the coupled system. The modal approach is adopted to determine the vibro-acoustic system's response which the numerical results show the importance of the viscothermal effects in the case of thin fluid layers.     

Prediction of the transient energy response for complex vibro-acoustic systems

As research works of the transient statistical energy analysis (TSEA) and transient local energy approach (TLEA) mostly focus on simple structures, TSEA and TLEA are adopted to quantify the transient response of a complex vibro-acoustic system at the mid-high frequency range in this paper. Numerical examples of a coupled oscillator system, an L-shaped plate, and a launch vehicle fairing model are conducted to demonstrate the effectiveness and accuracy of TSEA and TLEA. The computational precision of TSEA and TLEA is verified by the analytical solution and finite element method. Furtherly, the transient energy responses of subsystems with different coupling ratios between subsystems are investigated. Results show that TLEA has a better performance than TSEA. With the increasing coupling ratio between subsystems, the rise time and peak energy of transient energy response of subsystems decrease gradually. Both ratios of rise time and peak energy predicted by TLEA to these of the TSEA increase as the rising of the coupling ratio.

     

齿轮轴系参数匹配对系统不平衡响应的影响

研究了齿轮耦合轴系结构参数匹配对系统不平衡响应的影响.结果表明,齿轮耦合轴系的不平衡响应幅值的大小取决于系统转子之间的参数匹配,参数匹配得当,齿轮耦合将会对系统的不平衡响应起到很好的抑制作用,反之,将加剧系统的不平衡响应.     

横向磁通径向位移传感器研究

横向磁通传感器是一种对转子径向位移进行测量的新型传感器。与传统的涡流或电感式传感器相比,其凭借独特的探头设计,具有高性价比、高精度、高灵敏度、结构紧凑等优点。通过理论分析,研究了影响该传感器灵敏度的若干因素。建立有限元模型,通过仿真明确了传感器探头设计的要点,总结了设计规律。设计并优化实验电路,搭建实验平台完成了对传感器的性能测试,结果表明该传感器具有良好的灵敏度、线性度和极低的X-Y耦合度。将此传感器成功应用于某主动式磁轴承转子的位移检测,实现了稳定悬浮,并且转速达到了12 000 r/min。     

水下位移测量传感器的设计

这里介绍用于水下位移测量的磁力矩偶合旋转编码器的设计。在该旋转编码器的结构设计中将其转轴分隔为从动轴和主动轴,采用磁力矩耦合的原理,使旋转编码器内部检测元件处于完全密封的腔体内,以保证其正常工作,可用于密封要求严格或水下的机械位移测量。     

Dynamic modeling and analysis of axial vibration of a coupled propeller and shaft system

The dynamic and acoustic characteristics of a coupled propeller and shaft system which is modeled by the transfer matrix method are studied. The elasticity of the propeller is taken into consideration by employing the equivalent reduced modeling method. Thus the influence of the elastic propeller on the vibro-acoustic responses of the coupled system is investigated. To reduce the axial vibration of the coupled propeller-shaft system, the influence and location of the vibration isolator on the structural and acoustic responses is presented. Simulation results demonstrate that utilizing the relationship between the natural frequency of the propeller and the resonance frequency range of the shaft can control the vibration of the coupled system without other vibration control method. Utilizing a vibration isolator is another effective way to control vibration. The optimal position for the isolator installed between the shaft and the thrust bearing is investigated.     

Dynamic design for motorized spindles based on an integrated model

With increasing popularity in high-speed machining for its high efficiency, motorized spindles have been widely utilized in modern production facilities. Due to the combination of tools and built-in motors, the dynamic characteristics of motorized spindles are more complex compared with conventional spindles, and it is becoming necessary for engineers to thoroughly realize the influences of the system parameters to the system dynamics with considering the multi-physics coupling property. This paper presents an integrated model to study the electro-thermo-mechanical dynamic behaviors of motorized spindles. The integrated model consists of four coupled submodels as follows: bearing, built-in motor, thermal, and shaft model. Based on the proposed model, a design flow chart is developed and six design parameters are identified. The integrated model is validated experimentally and a design sensitivity analysis of the six parameters is then conducted based on a 170MD15Y20 type spindle. The results show that the integrated model is capable of accurately predicting the dynamic characteristics of motorized spindles, and the sensitivities of the six design parameters to the nature frequencies of the spindle system are obtained with and without the influence of the multi-physics coupling property. The coupling relationship among the electrical, thermal, and mechanical behaviors of the spindle system becomes clear from the results.