Simulation on a car interior aerodynamic noise control based on statistical energy analysis

How to simulate interior aerodynamic noise accurately is an important question of a car interior noise reduction. The unsteady aerodynamic pressure on body surfaces is proved to be the key effect factor of car interior aerodynamic noise control in high frequency on high speed. In this paper, a detail statistical energy analysis (SEA) model is built. And the vibra-acoustic power inputs are loaded on the model for the valid result of car interior noise analysis. The model is the solid foundation for further optimization on car interior noise control. After the most sensitive subsystems for the power contribution to car interior noise are pointed by SEA comprehensive analysis, the sound pressure level of car interior aerodynamic noise can be reduced by improving their sound and damping characteristics. The further vehicle testing results show that it is available to improve the interior acoustic performance by using detailed SEA model, which comprised by more than 80 subsystems, with the unsteady aerodynamic pressure calculation on body surfaces and the materials improvement of sound/damping properties. It is able to acquire more than 2 dB reduction on the central frequency in the spectrum over 800 Hz. The proposed optimization method can be looked as a reference of car interior aerodynamic noise control by the detail SEA model integrated unsteady computational fluid dynamics (CFD) and sensitivity analysis of acoustic contribution.     

轿车车内噪声统计能量仿真与降噪方法研究

对于受高频、宽频带随机激励的复杂车辆结构动力学响应及其噪声辐射问题,传统的计算方法难以获得满意结果.采用统计能量分析(SEA)方法对某国产轿车的车内声场进行了建模、仿真研究和声贡献分析,并以此为基础进行了车内噪声的改进设计,分别讨论了地板阻尼层、侧窗玻璃厚度和吸声材料对车内噪声的影响.通过计算各个子系统闻的能量流动,分析车内噪声的产生机理,讨论了不同吸、隔声材料对车内噪声响应特性的影响,研究结果可为车内声学设计提供参考.     

滚动轴承噪声与振动测试环境系统的改进

针对常规轴承噪声与振动测试环境系统的不足,提出一种更加完善的轴承噪声与振动测试系统。该系统采用房中房结构,内房和外房采用浮动连接,轴承驱动装置设计为穿墙驱动与无级调速等;测量载荷设计为无级可调,自动加载,测试装置所处环境的周边安装吸声尖劈,减少了外界环境的干扰。该测试环境系统用于测试和分析中小型家电轴承、电机轴承、汽车轴承、医疗器械等用各类轴承的噪声和振动,也可以测试轴承声压级噪声和声功率级噪声等。     

箱体结构的声固耦合有限元分析

基于声学有限元法和声固耦合理论,建立了箱体结构的有限元模型,采用有限元AN-SYS软件,针对不同厚度的壁板以及不同位置的加筋处理两种情况,对箱体结构振动与内部噪声进行了分析研究,确定部分结构参数的改变对箱体内部噪声的影响规律.     

非规则结构表面多声源近场声全息方法

为了提高非规则结构表面多声源声场的全息精度,提出基于目标深度识别与球面波叠加逼近的非规则表面多声源近场声全息方法。该方法使用声源空间深度识别理论,确定结构体上各声源的空间位置,在各声源处分别使用球面波的叠加描述空间声场分布,然后结合现有单原点球面波叠加近场声全息法重构声场。为了验证方法的可行性,首先使用所述方法和现有单原点球面波叠加声全息法,分别对径向脉动球与横向振动球组成的不同声场进行全息重构。结果表明,当声源集聚分布时,所述方法与现有方法均能有效全息重构声压分布,重构误差在5%以下;当声源离散分布时,现有方法失效,所述方法能够较准确地给出重构面的声压分布,主要频段内的全息重构误差小于20%。进一步的对比实验表明,在全息重构多扬声器非规则空间分布声场时,使用所述全息方法的重构误差平均下降14.08%,显著提升了多声源非规则空间分布声场的全息精度。     

模拟齿轮箱辐射声场的边界元分析和试验研究

在模拟齿轮箱辐射声场的分析中将全特解场边界元方法推广应用于声辐射问题的分析计算。通过模拟齿轮箱辐射声场的边界元分析和试验结果的对比,证实全特解场边界元方法应用于结构声辐射问题的分析计算同样是非常有效的。     

自由外翻式组合吸能装置的设计及优化

为研究三节直翻卷圆管轴向压缩下的吸能特性,采用非线性有限元软件LS-DYNA进行了仿真分析,发现当上圆管、下圆管壁厚越接近且上圆管厚度略大于下圆管时,载荷-位移曲线统一于一条平稳的水平线,圧缩力效率乘积可达0.838 7,比吸能可达15.342 8  J/g,冲程效率高达76%,接近理论值。针对三节直翻卷圆管冲程效率高、载荷十分平稳但比吸能欠缺的特点,在其内部填充波纹管和多胞管以提高总吸能及比吸能。结果表明：填充后形成的组合吸能装置延续了冲程效率高、载荷平稳的特性,相比单一直翻卷管,总吸能提高了105.75%,比吸能提高了26.28%。利用径向基函数代理模型及遗传算法对组合吸能装置的比吸能进行寻优,优化结果显示,最大比吸能在多胞管、波纹管壁厚分别取上限值、下限值时达到,且相比单一直翻卷管,其值提高了30.86%。     

非标压力机箱形主梁全约束优化设计

根据非标设备结构优化问题的特点,给出满足《钢结构设计规范》(GBJ17 88)规定的箱形主梁全约束优化设计方 法。将编制的内罚函数法优化程序应用于主梁的设计,计算结果表明,该优化方法可应用于实际设计。     

基于减振器设计的高速列车地板降噪特性研究

为解决铁路列车在轻量化、高速化的过程中带来的一系列车辆振动和噪声问题,针对已有车体结构,重点研究了地板减振器参数变化对改善车辆隔声性能的影响。首先,开展车内噪声特性及车内噪声源识别测试,探明车内噪声的显著频段、主要声源源强及分布特性;其次,对比分析地板内部安装减振器前后车辆噪声特性的变化,明确地板减振器的降噪效果;最后,运用基于声学实验室测试的方法对地板减振器各类参数开展研究和优化设计。研究表明:地板结构为车内噪声主要传声结构和声源分布区域;安装地板减振器可以有效提高地板结构的隔声量,从而达到抑制车内噪声的目的;改变地板减振器刚度、邵氏A硬度、阻尼、载重及数量均对地板结构隔声性能有一定影响。本研究可为轨道车辆减振降噪设计提供依据。     

高压水射流靶物探测用喷嘴结构参数优化

高压水射流靶物探测技术是一项结合了高压水射流技术和声音信号分类识别技术的新的技术和研究方向,要实现高压水射流对靶物的有效探测,就必须得到具有合理有效的特征值的信号。其中喷嘴结构是影响特征值信号的一个重要因素,在选择工程上常见的、结构较为合理的4种喷嘴的基础上,利用计算流体力学软件Fluent对喷嘴内部流场做了数值模拟分析,并从反射声信号的角度给出试验判定。试验结果表明,出口直径为0.8mm的圆锥长直线型喷嘴产生的射流性能及射流束的聚集性都较好,有利于产生较好反射声音信号的特征值。     

车身低噪声设计新方法

为降低车内低频噪声而改进车身结构时,现有方法往往需要较长周期,因此研究一种可快速、准确定位车身结构薄弱处,以及明确车身结构刚度调整方向的车身低噪声设计新方法。将一般腔体结构的内部声场计算公式分解为5个部分,并讨论这5个部分的特点,确定进行声压响应幅度判定参数研究时,采用的6种关键组合。以含一个弹性面的刚性长方体结构声腔耦合系统为对象,讨论6种关键组合的关系;分析发现振型耦合系数、频率重叠系数、结构振型在激励点处分量等三者的乘积能够完全体现声压响应信息,可作为声压响应幅度判定参数。详细分析声压响应幅度判定参数的特点,可满足预期研究目标;基于该参数,提出一种车身结构低噪声设计的新方法。利用该新方法,对某轿车车内低频噪声进行优化,进一步的频率响应计算结果表明,车身结构优化后驾驶员测点声压级平均降低3 dB,最大降低10 dB。     

飞行器结构在高强宽频噪声环境下的响应预示分析与试验研究

超高声速飞行器的动力学环境频域宽,使用有限元/边界元方法预示其振动响应存在困难。基于统计能量分析(Statistical energy analysis,SEA)理论建立某型高速飞行器声振耦合动力学模型,用理论解析和经验公式的方法确定各子系统的输入参数,以实际噪声试验条件作为飞行器SEA模型的输入激励,对飞行器舱内噪声声压级和子系统振动加速度响应进行预示,并与试验结果进行比较。结果显示,子系统振动加速度功率谱密度(Power spectral density,PSD)在中高频与试验结果基本一致,舱内声压在整个频段内误差小于3 d B,因此建立的动力学模型和采用的计算方法是可靠的,解决了有限元、边界元在中高频声振响应问题计算的局限性。通过传递路径分析寻找出舱内声场的主要来源,提出以损耗因子为设计变量的噪声控制与优化方法,利用遗传算法实现了这一非线性约束问题求解,为研究飞行器结构和复杂动力学环境以及飞行器降噪优化设计提供有效的手段。     

Investigation of beam-plate systems including indirect Coupling in terms of Statistical Energy Analysis

Statistical Energy Analysis (SEA) is generally used for the high frequency analysis in various areas. In the present paper a SEA-related study concerning coupled structures consisting of beams and plates is discussed. Firstly, the Fourier technique is explained to obtain the energies and power flows for excitation on the beam and the plate. Then, these are used in the Power Injection Method (PIM) to obtain the effective Coupling Loss Factors (CLFs) of the single beam-plate system. Overlapping octave bands are used in a frequency average approach. Based on the analysis for the beam-plate structure, the beam-plate-beam structure is also investigated in the SEA framework. It is found that the indirect coupling in an SEA sense may exist for such a beam-plate-beam coupled structure. The numerical result shows that its effect is larger when the dimensions of beams are similar.     

Parametric approaches for uncertainty propagation in SEA

A limit of statistical energy analysis (SEA) is that of providing only the mean values of the mechanical energy of a vibrating system. In this paper, the variability of SEA solution under uncertain SEA parameters (coupling loss factors, internal loss factors and injected powers) is investigated by comparing a sensitivity approach and a design of experiment (DoE) approach. Uncertainties of the SEA parameters depend on uncertainties in the physical properties of the considered mechanical system. Numerical results are derived using a benchmark structure made by three aluminum plates with a common junction and a launcher fairing. The analysis of the effect of uncertainties of SEA parameters can be used for design purposes, i.e. to identify which are the most effective areas to modify in order to control the energy level of a given subsystem.     

轿车声学建模的统计能量法

针对高频域的声场，提出了基于能量理论的等效声源法对轿车的发动机室进行声场建模，采用统计能量法(SEA)理论对发动机室、发动机室底板及底板与地面空间系统进行声场建模和仿真。该方法简单、实用，利于工程应用。能很好地解释系统的声场物理特性。     

玻璃钢包装箱气体密封结构及压差控制系统设计与试验

提出一种用于贵重精密仪器公路运输的包装箱。该包装箱由钢骨架及玻璃钢材料制成，具有气体密封性能及压差自动调节能力。阐述了包装箱的箱门、操作窗及穿舱件的密封结构设计；同时介绍了包装箱压差调控气路系统的设计，可随环境温度及大气压的变化自动充气与排气，控制箱体内外压差维持在0.5×10-3～3×10-3  MPa之间；并通过定积容器的充、放气时间计算方法，按照绝热充气与绝热膨胀过程，计算了充气及排气的时间；最后通过充排气试验与保压试验，验证了箱体的压力调控性能及密封性能，为大型气密性包装箱的设计及研制提供了参考。     

Is it possible to treat confidentially SEA the wolf in sheep's clothing?

At present, Statistical Energy Analysis (SEA) is the most acknowledged tool for the solution of high-frequency problems.However, a reliable solution can be obtained by SEA only if particular conditions are satisfied. In other words, the basic hypotheses would define the range of applicability of this method.Two important parameters, coupling loss factor (CLF) and internal loss factor (ILF), play a key role in describing the power transmitted between subsystems and the power dissipated by each of them. The coefficients of the SEA equations depend on these parameters, while the known terms are the powers injected into each subsystem. Theoretical relationships allow to predict the CLFs and ILFs of simple subsystems, but very often the theoretical estimate of these parameters is incorrect and their values may be rather obtained experimentally.The aim of this paper is addressed to analyse whether a particular vibroacoustic problem can be efficiently solved by SEA. This is an initial attempt to provide the SEA user with a simple tool indicating if a SEA model can provide a significant result for the particular problem under study. The basic hypotheses involving the SEA parameters are systematically presented and translated into mathematical relationships to provide such tool.To check the validity of this approach two cases are analysed. First, a simple vibroacoustic problem, where the SEA parameters are theoretically determined, is studied. Then a more complex system, the case of three coupled plates is considered: the energy in the system is experimentally determined. Such result is then compared with the results of the SEA model: it is shown that, whenever the comparison is good or not, the mathematical hypotheses of SEA provide a significant a priori evaluation of the SEA efficiency.     

KYN28A型开关柜内部故障的电弧结构设计

开关柜内部电弧故障会引起许多效应,巨大的电弧能量将周围的空气迅速加热,引起柜内压力瞬间升高。为了操作人员和设备的安全,必须对开关柜结构进行强化设计,使其能抵御内部故障电弧能量的冲击。对此改进做了分析试验,得出了有效的结论。     

工程机械驾驶室内部噪声预估分析

基于统计能量分析（SEA）原理,建立了某工程机械驾驶室SEA模型,通过Hilbert变换瞬态衰减法测试了模型中所需要用到结构件的内损耗因子,仿真计算结果与实测值趋势一致;通过1／3倍频程分析,发现部分中心频段数值相差较大,分析发现主要为一些过线孔、缝未处理,修正SEA模型后仿真计算结果与实测值基本吻合,噪声能量误差仅为8．2％;同时通过分析驾驶室内部噪声的主要能量来源,对能量输入的主要部位进行了降噪处理,仿真计算结果降低了2．5dB,与实测结果降低了2．3dB非常接近,表明统计能量分析方法能够准确预测驾驶室内部噪声,为产品早期开发阶段提供准确的设计依据．     

防水透气阀在雷达密封腔体中的应用

文中介绍了防水透气阀在雷达密封腔体组件上的应用,对防水透气阀能够平衡腔体内外压力、避免结构变形引起密封失效和消除因"呼吸效应"产生积水等现象进行了探讨,并对密封腔体内的气体状态进行了计算,对腔体结构受力变形进行了仿真分析,为防水透气阀的选型提供了理论依据。试验验证和随机试用表明,防水透气阀能够改善密封腔体内元器件的工作环境,提高组件的可靠性。