车身结构与车内空腔流固耦合系统的模态分析

为研究汽车的振动噪声特性,利用ANSYS软件采用板壳、梁和流体单元建立某车身结构及车内空腔的有限元模型,其中,将车身结构作为弹性体,乘员室内的空气作为流体.通过对车身结构、车内空腔流体及车身与车内空腔流体的耦合结构进行模态分析,并对比计算结果,得到它们之间的相互关系,有利于整车振动和噪声特性的研究.     

地铁列车车内低频结构噪声仿真

建立某地铁列车车体结构和车内声腔有限元模型,进行声固耦合模态分析,得到车体结构和车内声腔的模态特征。将车体动力学模型计算得到的车体振动激励施加于声固耦合模型中,分析地铁列车车内低频噪声和车身板件声压贡献量,得到对观察点声压贡献较大的板件,有针对性地提出车体结构改善方案,降低观察点处的噪声,为地铁列车车内噪声优化提供指导。     

汽车车内噪声主动控制系统仿真

降低汽车空腔的振动,是抑制汽车车内噪声的有效途径之一;以激振器、作动器和控制器等为主要部件,搭建了简化的汽车车内噪声主动控制系统,该系统通过将汽车空腔模型简化为板件,以减弱板件振动为目标,实现了汽车车内噪声主动控制;采用简谐正弦及余弦信号作为激振器发出的激励,用于模拟板件的初始振动,控制器通过采用模糊控制算法直接控制压电陶瓷作动器的振动,压电陶瓷作动器的振动用于抑制板件的振动,完成了汽车车内噪声主动控制系统仿真;仿真结果表明,研究采用的汽车车内噪声主动控制系统,使汽车空腔振动降低23%,为解决由汽车发动机和动力总成的振动所引发的汽车车内噪声问题提供了一个有效途径。     

基于FCV声固耦合模型的车内噪声预测

为了更精确地对燃料电池轿车(FCV)的车内噪声进行仿真研究,在详细的车身结构有限元模型和乘座室声学有限元模型基础上,建立了多子系统声固耦合模型,并进行了声固耦合模态分析。将试验所得的激励信号加载于该模型进行频响分析,得到车内噪声的响应量与实验值基本吻合。故多子系统的声固耦合模型较真实地反映了燃料电池轿车的振动噪声特性,为进一步的模态参与分析和板件贡献分析打下了基础。     

A型地铁车内噪声分析和优化

为研究轨道车辆轻量化带来的车内振动噪声问题,基于某A型地铁车辆的有限元模型,建立其声学计算模型,以车体板件频率响应的振动位移结果作为声学激励,在车内布置ISO标准场点进行车内噪声分析.结果显示,车内各点声压级在频域上分布极不均匀,且普遍存在几个较大的峰值.分析目标板件的振动,提出几种减振降噪的优化方案.对比各方案发现,增加板件强度后振动和噪声都相应地减小;减振降噪需综合考虑优化后车体的整体强度和动力学性能.     

开闭件声腔对噪声传递函数分析的影响

为了准确地仿真分析汽车的NVH特性,通常需要准确获取声腔的声学特性参数。以某内饰车身为研究对象,以车内声学特性机理为基础,为探索开闭件声腔模型对噪声传递函数仿真分析的影响,分别建立了传统车内声腔模型的声固耦合系统和附加开闭件声腔的车内声固耦合系统。采用以声腔模态分析、板件贡献量分析、原点动刚度分析三种CAE仿真分析方法并结合所选车型的仿真NTF曲线特点,有针对性地分析了开闭件声腔在声腔建模时需要被考虑的原因。并通过试验验证了模型的准确性和方法的有效性。结果表明,附加开闭件声腔的建模仿真更接近实际情况,使得仿真更准确。     

基于混合LES/BEM方法的汽车侧窗结构风振噪声分析

利用大涡模拟（Large Eddy Simulation,LES）方法对某轿车的侧窗风振噪声进行计算,其结果与整车道路测试实验结果吻合良好.对相应流场下的车窗进行结构振动特性计算,结果表明汽车高速行驶时车窗结构受内外气流影响会产生微米级的振动.据此振动结果,运用边界元法（Boundary Element Method,BEM）模拟车内辐射声场分布、场点声压频率响应以及车窗板件声学贡献量,结果表明汽车开窗高速行驶时,风振噪声是汽车高速行驶时驾驶员耳旁噪声的主要来源,但在某些频率下车窗辐射声场会有明显的声学响应,其中后窗的辐射声压贡献量占主要部分,开启的侧窗声学贡献量要高于其他侧窗的声学贡献量.     

70%低地板轻轨车车内噪声分析和降噪优化

针对城市轨道交通振动噪声问题突显、制造平稳低噪的城市轨道列车的需求较大的问题,研究70%低地板轻轨车车内噪声.建立无内装70%低地板轻轨车体有限元模型及其声学计算模型;以车体板件频率响应的位移振动结果作为声学激励,在车内布置ISO标准场点,获得车内噪声分析结果.将声压峰值处的频率作为目标频率,分析该频率处各低场点的板件贡献量,并确定目标板件;针对目标板件的振动,制定简便易行的降噪优化方案;对比降噪前后的车内声压值,归纳出一套可行的无内装70%低地板轻轨车体降噪方法.     

车辆驾驶室降噪设计与仿真研究

研究驾驶室内噪声是车辆乘坐舒适性问题,由于车身的振动产生噪声,车辆的舒适性差.为了降低室内噪声通过对驾驶室进行试验模态分析,得出周有频率和基本振型变化,发现频率为120.44Hz时驾驶室内噪声影响最大.对驾驶室壁板采用辛几何解析法和面板声学贡献度分析,得出对顶板驾驶员耳旁声压级影响最大.为解决上述问题,对驾驶室顶板采用加筋板的降噪方法,利用声辐射理论,对改进后的驾驶室降噪效果进行数值仿真,得出改进后驾驶室内的声压降低了10.3dB,有效的抑制了低频噪声,提高了车辆的舒适性.     

Abaqus在车身外覆盖件抗凹性分析中的应用

车身外板是汽车车身上重要的外覆盖件,但结构特征少、局部刚度弱.客户在选购车辆时,可能会对车身外覆盖件表面进行按压,如果刚度不足,容易导致大面积变形,影响客户对车辆的印象.为在设计初期保证车身外板的抗凹性能,降低后期问题的出现,以某车型车身外板为例,阐述应用Abaqus进行表面抗凹陷特性分析和优化过程,结果能够满足客户的使用要求.     

Bead pattern optimization

Plane sheet panels exhibit poor stiffness and NVH (noise, vibration, and harshness) performance due to their flexibility. A common and cost-effective approach in the automotive industry to improve the stiffness and NVH peformance of sheet panels is the addition of beads. However, no systematic methodology is available for determining the optimal pattern of beads in sheet metal. This research explores the feasibility of applying topology optimization methods to the bead design of sheet panels. The approach starts with adding beam elements to the shell element model of the sheet panel to simulate the stiffness improvement of the structure and then uses the topology optimization method to obtain the optimal layout of the beam elements. A cantilever plate is used to perform a preliminary study for bead pattern design and a simplified vehicle structure is used to demonstrate the applicability of the proposed method.     

On objective functions of minimizing the vibration response of continuum structures subjected to external harmonic excitation

This work deals with the topological design of vibrating continuum structures. The vibration of continuum structure is excited by time-harmonic external mechanical loading with prescribed frequency and amplitude. In comparison with well-known compliance minimization in static topology optimization, various objective functions are proposed in literature to minimize the response of vibrating structures, such as power flow, vibration transmission, and dynamic compliances, etc. Even for the dynamic compliance, different definitions are found in literature, which have quite different formulations and influences on the optimization results. The aim of this paper is to provide a comparison of these different objective functions and propose reference forms of objective functions for design optimization of vibration problems. Analytical solutions for two degrees of freedom system and topological design of plane structures in numerical examples are compared using different optimization formulations for given various excitation frequencies. The results are obtained by the finite element method and gradient based optimization using analytical sensitivity analysis. The optimized topologies and vibration response of the optimized structures are presented. The influence of excitation frequencies and the eigenfrequencies of the structure are discussed in the numerical examples.     

Optimal rib layout design for noise reduction based on topology optimization and acoustic contribution analysis

In this paper, an optimum rib layout design method for reducing radiated noise is proposed based on topology optimization and acoustic contribution analysis. According to radiated noise depends on acoustic transfer vector (ATV) and normal velocity, the influence of rib layout on ATV is analyzed and it is found rib layout has little influence on ATV. Only if a region has maximum acoustic contribution, the normal velocities on this region can have the most remarkable influence on radiated noise. So the determination procedure of region with maximum acoustic contribution is introduced. Based on this, the topology optimization model is established to minimize the normal velocities on this region. Ribs can be arranged according to the optimum topologies to reduce the normal velocities, which in turn results in a reduction of radiated noise. The topology optimization model is used to obtain the optimal rib layout by taking a plate-like structure as an example. The plate is fixed along all side edges and excited by a time-harmonic external point load with different prescribed frequencies. The radiated noise is simulated using the finite element method and boundary element method. Four plates are manufactured according to the optimal rib layouts for different single frequency excitation. Modal test and sound measurement are conducted to validate the proposed method. The influence of loading position on the topology optimization results is also investigated and discussed.     

基于Tosca的油底壳振动性能条纹优化

发动机油底壳的振动噪声是发动机辐射噪声的主要来源,对其进行振动性能的优化具有积极意义.在传统的拓扑优化和形状优化设计中缺乏对油底壳振动响应特性的研究.基于Tosca中的条纹优化技术,考虑表面振动速度响应对油底壳进行优化.结果表明优化后的设计方案的振动性能得到极大改善;条纹优化技术可以充分挖掘结构设计潜力,是一种非常有效的优化方法.     

基于多模型拓扑优化方法的车身结构概念设计

为获得最优的初始设计方案,在车身概念设计阶段对车身结构进行拓扑优化。车身结构性能指标综合考虑整体刚度、局部动态刚度和碰撞性能,采用多模型优化(multi-model optimization,MMO)方法解决此类复杂工况的拓扑优化问题,通过调节设计空间和设置参数,获得车身最优载荷路径。根据拓扑优化结果初步形成车身框架结构,可为后期详细设计提供参考。     

On topology optimization of damping layer in shell structures under harmonic excitations

This paper investigates the optimal distribution of damping material in vibrating structures subject to harmonic excitations by using topology optimization method. Therein, the design objective is to minimize the structural vibration level at specified positions by distributing a given amount of damping material. An artificial damping material model that has a similar form as in the SIMP approach is suggested and the relative densities of the damping material are taken as design variables. The vibration equation of the structure has a non-proportional damping matrix. A system reduction procedure is first performed by using the eigenmodes of the undamped system. The complex mode superposition method in the state space, which can deal with the non-proportional damping, is then employed to calculate the steady-state response of the vibrating structure. In this context, an adjoint variable scheme for the response sensitivity analysis is developed. Numerical examples are presented for illustrating validity and efficiency of this approach. Impacts of the excitation frequency as well as the damping coefficients on topology optimization results are also discussed.     

Evolutionary natural frequency optimization of thin plate bending vibration problems

This paper extends the evolutionary structural optimization method to the solution for maximizing the natural frequencies of bending vibration thin plates. Two kinds of constraint conditions are considered in the evolutionary structural optimization method. If the weight of a target structure is set as a constraint condition during the natural frequency optimization, the optimal structural topology can be found by removing the most ineffectively used material gradually from the initial design domain of a structure until the weight requirement is met for the target structure. However, if the specific value of a particular natural frequency is set as a constraint condition for a target structure, the optimal structural topology can be found by using a design chart. This design chart describes the evolutionary process of the structure and can be generated by the information associated with removing the most inefficiently used material gradually from the initial design domain of a structure until the minimum weight is met for maintaining the integrity of a structure. The main advantage in using the evolutionary structural optimization method lies in the fact that it is simple in concept and easy to be included into existing finite element codes. Through applying the extended evolutionary structural optimization method to the solution for the natural frequency optimization of a thin plate bending vibration problem, it has been demonstrated that the extended evolutionary structural optimization method is very useful in dealing with structural topology optimization problems.     

轿车排气管挂钩刚度优化分析

针对某轿车在试车场进行耐久性试验时出现挂钩处开裂的问题,建立考虑动力总成的排气系统振动分析模型;通过频率响应分析发现挂钩开裂处的约束反力稍大,局部刚度偏低;通过结构优化使挂钩刚度得到加强.对2种优化方案的对比表明优化后的挂钩能减小排气系统传递到车身地板的振动,提高排气系统的疲劳寿命.