登录
首页 » Others » 汽车噪声与振动-理论与应用

汽车噪声与振动-理论与应用

于 2020-12-05 发布
0 313
下载积分: 1 下载次数: 2

代码说明:

汽车NVH领域的经典入门读物,引领进入汽车振动噪声研究的最佳选择。第一章管道声学(1.12)时,声压幅值达到最大,反节点的位子是:(1.13)驻波是由频率相同的向右传播的入射波和向左传播的反射波迭加而成。驻波并不是运动的波,而是静止的,这是“驻”波名称的由来。波表示管道中的声音的模态。对於长度一定的管道来说,由于有许多频率的波,因此也就有很多驻波。这里所提到的驻波是假设管壁刚硬,所冇声波遇到管壁时全部被反射回来。可是实际上,管端壁不是完全刚性,因此反射波的声压不完全等於入射波声压,因此在节点处,入射波和反射波不可能完全抵消。但是这些点处的声压大部分被抵消,声压最低。第二节管道声阻抗阻抗是指当对媒质受到压力或者搾动力时,媒质会对传播产生阻碍。管道中的声学阻抗Z,定义声压与质点体积速度的比值,即(1.14)式中,u,U和S分别是管道中的速度,体积速度和截面积。体积速度与质点速度的关系为:L=SL。声吝在管道內传播,当管道的截面积发生变化的时候,声阻抗也发生变化。图1.3是截面积变化的管道,在变截面的地方,由于阻抗发生变化,一部分入射波就会被发射回原来的管道而另一部分入射波会在新的截面管道中继续传播。抗性消音器的工作原就是基于这种阻抗的变化。声波从发动机出来并在进气或者排气系统中传播,当遇到消音元件或者截面积变化时,入射声波被反射回发动机声源,从而抑制声音的传播。进排气系统中声阻抗不匹配的情况主要有截面积变化,主管道中插入了其他管道(如旁支消音器等),管道开口通往大气等等图1.3截面积变化的管道进排气系统中管道的长度都是有限的。图1.4表小一个长度为L的管道。假改管道两端的声阻抗分别已知,即在=处,声阻抗为,在=处,声阻抗为由公式(1.6)和(1.9),可以得到管道中仟一点的声阻抗为管道声学图1.4长度为L的管道将=代入公式(1.15)中,得到该处的声阻抗为:将三代入公式(1.15)中,得到该处的声阻抗:公式(17)可以重新写成下面的形式18将方程(1.16)代入到方程(1.18中,消除和,就得到输入声阻抗和输出声阻抗的关系,如下第一章管道声学(1.20第三节管口封闭与管口敞廾声波从管道入口端发射出来,传播到尾端。管道尾端通常有两种情况,一种是开口的,如进气管口,排气尾管口;另一种是封口的,如四分之一波长管。下面就来分析这两种尾端的声学特征。1.开∏-封闭管道图1.5表示管道尾端封闭状况。声音在管道里问石传播,当声波碰到刚性的封闭端时,声波被全部反弹冋来,再向左传播管口封闭图1.5开凵封闭管道对一个刚性的封闭口来说,其声阻抗为无穷大,即>0,根据公式(1.19),得到:1.21)声阻抗可以写成下面的形式:(1.22)式中R和粉别是阻抗的实部和虚部,R为声阻,称为声抗。声阻取决于结构的材料特性,而声抗则取决」结构的儿何特性。当声抗为零的时候,结构就发生共振。公式(1.21)中的声阻抗也可以写成公式(1.22)那样的形式,为(1.23)上式如果满足下亩的条件:(1.24)即,那么这个开口-封闭管道就发生共振,其固有频率为:(1.25)当n-=1,2,3,.,时,分别对应著管道第·阶、第二阶、第三阶,,.,等阶次频率图1.6是管道声波的第一阶和第阶模态。这个声波在封闭端时,声压达大最大值,然后发射第一章管道声学到入口处,使得入口端的声压为零,即在开口端形成驻波节点。四分之一波长管就是应用这个原理来工作的。图1.6管道声波的第一阶模态(A)和第二阶模态(B)公式(1.25)可以转变为管道长度与波长的关系,表达如下1.26)当n=1时,管道的长度是波长的四分之,即:。所以这种开∏封闭的管道通常叫著四分之一泼长管2.开口开口答道图1.7为一个尾端开口的管」。声波从入口端向右传播进入开口端时,声音与大气产生声耦合。大气的辐射声阻抗会将一部分声波返回管口敞开图1.7开口-开口管道声波在尾端的声阻抗为周围坏境的声阻抗,也就是说这个声阻抗不为零。为了使问题简化起见,我们先假设这个阻抗为零,然后再对所得到的结构进行修正。如果在x=处的声阻抗为零,那么由公式(1.19)可以得到下式(1.27)同样,当这个声阻抗中的声抗为零的吋候,管道就发生共振,这时必须满足:即:这时,开口-开口管道的共振频率为:当n=1,2,3,,时,分别对应著管道第一阶、第二阶、第三阶,.,等阶次频率第一章管道声学图1.8是开口-开口管道声波的第一阶和第二阶模态。图1.8开口-开口管道的第一阶模态(A)和第二阶模态(B)公式(1.30)可以转变为管道长度与波长的关系,衣达如下(1.31)3.开口管道的修正在推导尾端廾口公式时,我们假设了出口周围坯境的声阻抗为零,但是实际上这个阻抗不为零,因此必须对公式(1.27-1.31)的结论做修止。对图1.9这样的开∏终端,被称为自由自由开口。该开口处的声阻抗为:等效管图1.9自山开口-开口修正管道山于管道的直径非常小,因此和都远远小于1。山公式(1.27)和(1.32)得到:(1.33)这样,管道内的频率为34)管道长度与波长的关系为(1.35这样管道的长度比声阻抗为零的时候要短些,也就是说好像有一根等效的延长管与原来的管道相连接。管道的计算长度就是实际管子长度加上等效延长管长度△即第一章管道声学(1.36有时侯,在出口管处还会加类似与法兰的结构,如图1.10所示。这时,有效延长管的长度为△实际管子的长度为:△式中是管子的计算长度发等效管图1.10法兰开口-开口修正管道第四节四端网终分析进气系统或者排气系统都是有很多管道和消音元件组成。分析整个系统往往是非常复杂的,但是如果将系统分解到一些小的段落,那么分析起来就相对容易些。得到了每个段落或者是每个部件的分析结果,然后将之合成起来就得到了整个系统的结果。四端网络分析就是这种分析方法,在管道声学分析中得到了广泛的应用。对於管道中一小段质量(如图1.11)来说,动力方程可以写成如下:(1.39)式中,S是管道的截面积,是这个小质量段的长度,和分别是质量端两边的压力图1.11管道中一小段质量的受力分析公式(1.39)可以表达为(1.40)第一章管道声学对这一小段质量来说,假设两边的速度是相等的,即将这公式(1.40)和(1.41)写成矩阵形式,得到:(1.42)公式(1.42)建立起这段小质量块两边的压力和速度的关系。管道中小段质量块后端的压力和速度可以用它前端的压力和速度来表示。也就是说质量块后端与前端之间建立起来一种传递关系。同样对一个长度为L的管道(如图1.4所示)也可以得到管道两端的传递关系。在=处的压力和速度可以通过公式(1.6)和(1.9)分别求得(1.13)由以上两式可以得到和,如下:45(1.46根据公式(6)和(9),在处的压力和速度分别为将公式(1.45)和(1.46)中和的表达式代入公式(1.47)和(1.48)之中,就得到管道入冂与出∏之间声压和速度之间的关系,为:+49将公式(1.49)和(1.50)写成如下的矩阵形式第一章管道声学这样就得到了管道两边的压力和速度的传递关系。公式(1.51)可以简单地写成如下形式式中,被称为传递矩阵。如果管道的传递矩阵知道,那么只要知道管道端的压力和速度,就可以通过传递矩阵算出另一端的压力和速度。在传递矩阵两边分别是两个输入参数和两个输出参数。这四个参数的关系由传递矩阵来确定,因此这种表达方式称为四端网络法。上面介绍了小段质量和长度为L的管道的传递矩阵表达方法。这种方法可以推广到任何一个声学元件,其输入端和输出端的声压和速度都可以用四端网络米表示。图1.12代表某个声学元件i。图1.12一个管道元件的四端网终图这个元件两边的压力和速度关系为式中是传递矩阵,是传递矩阵系数。汽车的进气系统包括进气管道、空气过滤器、赫耳姆兹消音器、四分之波长管等。排气系统包括排气多支管、催化器、谐振器、消音器和管道等。一个系统如果由N个元件组成。而且每个元件的传递矩阵都知道,那么出声口的声压和速度就可以用声源的声压和速度来表示如下形式:(1.54)式中的L1是系统的传递矩阵,如下形式(1.55)

下载说明:请别用迅雷下载,失败请重下,重下不扣分!

发表评论

0 个回复

  • Watershed Superpixel
    分水岭超像素,包含代码和论文,Watershed SuperPixel, IEEE ICIP2015,
    2020-12-03下载
    积分:1
  • matlabcode(与瑞利信道相关的OFDM仿真)
    matlabcode(与瑞利信道相关的OFDM仿真)
    2020-12-04下载
    积分:1
  • matlab读取地震segy数据
    matlab读取地震数据segy,(之前在csdn下载的别人的读取segy的那个文件有问题,请注意:读取之后每道的数据会发生变化请注意!!!)该文件读取后的道数据是存在Data变量之中。使用例子如下:[Data,SegyHeader,SegyTraceHeadersBinary]=ReadSegyFast(filename);
    2020-04-10下载
    积分:1
  • excel和json相互转换
    自己写的工具,可以很方便的使用excel和json进行相互转换,生成在同级目录
    2020-12-07下载
    积分:1
  • LCD1602篮球比赛计分器
    本课题设计采用单片机AT89C51为核心,设计出篮球计分计时系统,可以实现单节比赛12分钟倒计时、24秒进攻时间倒计时、开始/暂停倒计时、改变节次、单节结束报警、两队比分分别加1分、加2分、加3分等各种显示效果。本系统利用LCD1602液晶显示器作为显示器件,显示节次、12分钟倒计时、24秒倒计时、主客队双方比分,通过3*3矩阵键盘来控制计时器和计数器工作,单节比赛结束时LED发光二极管闪烁报警。该设计采用LCD1602液晶显示器,因为其微功耗、小体积、使用灵活等诸多优点在袖珍式仪表和低功耗应用系统中得到越来越广泛的应用,通过仿真基本上实现了上述功能,操作简单,性能稳定,符合一般篮球计分器
    2021-05-06下载
    积分:1
  • Lectures on Stochastic Programming-Model
    这是一本关于随机规划比较全面的书!比较难,不太容易啃,但是读了之后收获很大。这是高清版的!To Julia, Benjamin, Daniel, Nalan, and Yael;to Tsonka Konstatin and Marekand to the memory of feliks, Maria, and dentcho2009/8/20pagContentsList of notationserace1 Stochastic Programming ModelsIntroduction1.2 Invento1.2.1The news vendor problem1.2.2Constraints12.3Multistage modelsMultiproduct assembl1.3.1Two-Stage Model1.3.2Chance Constrained ModeMultistage modelPortfolio selection131.4.1Static model14.2Multistage Portfolio selection14.3Decision rule211.5 Supply Chain Network Design22Exercises2 Two-Stage Problems272.1 Linear Two-Stage Problems2.1.1Basic pi272.1.2The Expected Recourse Cost for Discrete Distributions 302.1.3The Expected Recourse Cost for General Distributions.. 322.1.4Optimality Conditions垂Polyhedral Two-Stage Problems422.2.1General Properties422.2.2Expected recourse CostOptimality conditions2.3 General Two-Stage Problems82.3.1Problem Formulation, Interchangeability482.3.2Convex Two-Stage Problems2.4 Nonanticipativity2009/8/20page villContents2.4.1Scenario formulation2.4.2Dualization of Nonanticipativity Constraints2.4.3Nonanticipativity duality for general Distributions2.4.4Value of perfect infExercises3 Multistage problems3. 1 Problem Formulation633.1.1The general setting3.1The Linear case653.1.3Scenario trees3.1.4Algebraic Formulation of nonanticipativity constraints 7lDuality....763.2.1Convex multistage problems·763.2.2Optimality Conditions3.2.3Dualization of Feasibility Constraints3.2.4Dualization of nonanticipativity ConstraintsExercises4 Optimization models with Probabilistic Constraints874.1 Introduction874.2 Convexity in Probabilistic Optimization4.2Generalized Concavity of Functions and measures4.2.2Convexity of probabilistically constrained sets1064.2.3Connectedness of Probabilistically Constrained Sets... 113Separable probabilistic Constraints.1144.3Continuity and Differentiability Properties ofDistribution functions4.3.2p-Efficient Points.1154.3.3Optimality Conditions and Duality Theory1224 Optimization Problems with Nonseparable Probabilistic Constraints.. 1324.4Differentiability of Probability Functions and OptimalityConditions13344.2Approximations of Nonseparable ProbabilisticConstraints134.5 Semi-infinite Probabilistic Problems144E1505 Statistical Inference155Statistical Properties of Sample Average Approximation Estimators.. 1555.1.1Consistency of SAA estimators1575.1.2Asymptotics of the saa Optimal value1635.1.3Second order asStochastic Programs5.2 Stoch1745.2.1Consistency of solutions of the SAA GeneralizedEquatio1752009/8/20pContents5.2.2Atotics of saa generalized equations estimators 1775.3 Monte Carlo Sampling Methods180Exponential Rates of Convergence and Sample sizeEstimates in the Case of a finite Feasible se1815.3.2Sample size estimates in the General Case1855.3.3Finite Exponential Convergence1915.4 Quasi-Monte Carlo Methods1935.Variance-Reduction Techniques198Latin hmpling1985.5.2Linear Control random variables method200ng and likelihood ratio methods 205.6 Validation analysis5.6.1Estimation of the optimality g2025.6.2Statistical Testing of Optimality Conditions2075.7Constrained Probler5.7.1Monte Carlo Sampling Approach2105.7.2Validation of an Optimal solution5.8 SAA Method Applied to Multistage Stochastic Programmin205.8.1Statistical Properties of Multistage SAA Estimators22l5.8.2Complexity estimates of Multistage Programs2265.9 Stochastic Approximation Method2305.9Classical Approach5.9.2Robust sA approach..23359.3Mirror Descent sa method235.9.4Accuracy Certificates for Mirror Descent Sa Solutions.. 244Exercis6 Risk Averse Optimi2536.1 Introductio6.2 Mean-Risk models.2546.2.1Main ideas of mean -Risk analysis546.2.2Semideviation6.2.3Weighted Mean Deviations from Quantiles.2566.2.4Average value-at-Risk2576.3 Coherent risk measures2616.3.1Differentiability Properties of Risk Measures2656.3.2Examples of risk Measures..2696.3.3Law invariant risk measures and Stochastic orders2796.3.4Relation to Ambiguous Chance Constraints2856.4 Optimization of risk measures.2886.4.1Dualization of Nonanticipativity Constraints2916.4.2Examples...2956.5 Statistical Properties of Risk measures6.5.IAverage value-at-Ris6.52Absolute semideviation risk measure301Von mises statistical functionals3046.6The problem of moments306中2009/8/20page xContents6.7 Multistage Risk Averse Optimization3086.7.1Scenario tree formulation3086.7.2Conditional risk mappings3156.7.3Risk Averse multistage Stochastic Programming318Exercises3287 Background material3337.1 Optimization and Convex Analysis..334Directional Differentiability3347.1.2Elements of Convex Analysis3367.1.3Optimization and duality3397.1.4Optimality Conditions.............3467.1.5Perturbation analysis3517.1.6Epiconvergence3572 Probability3597.2.1Probability spaces and random variables7.2.2Conditional Probability and Conditional Expectation... 36372.3Measurable multifunctions and random functions3657.2.4Expectation Functions.3687.2.5Uniform Laws of Large Numbers...,,3747.2.6Law of Large Numbers for Random Sets andSubdifferentials3797.2.7Delta method7.2.8Exponential Bounds of the Large Deviations Theory3877.2.9Uniform Exponential Bounds7.3 Elements of Functional analysis3997.3Conjugate duality and differentiability.......... 4017.3.2Lattice structure4034058 Bibliographical remarks407Biibliography415Index4312009/8/20pageList of Notationsequal by definition, 333IR", n-dimensional space, 333A, transpose of matrix(vector)A, 3336I, domain of the conjugate of risk mea-C(X) space of continuous functions, 165sure p, 262CK, polar of cone C, 337Cn, the space of nonempty compact sub-C(v,R"), space of continuously differ-sets of r 379entiable mappings,176set of probability density functions,I Fr influence function. 3042L, orthogonal of (linear) space L, 41Sz, set of contact points, 3990(1), generic constant, 188b(k; a, N), cdf of binomial distribution,Op(), term, 382214S, the set of &-optimal solutions of theo, distance generating function, 236true problem, 18g(x), right-hand-side derivative, 297Va(a), Lebesgue measure of set A C RdCl(A), topological closure of set A, 334195conv(C), convex hull of set C, 337W,(U), space of Lipschitz continuousCorr(X, Y), correlation of X and Y 200functions. 166. 353CoV(X, Y, covariance of X and y, 180[a]+=max{a,0},2ga, weighted mean deviation, 256IA(, indicator function of set A, 334Sc(, support function of set C, 337n(n.f. p). space. 399A(x), set ofdist(x, A), distance from point x to set Ae multipliers vectors334348dom f, domain of function f, 333N(μ,∑), nonmal distribution,16Nc, normal cone to set C, 337dom 9, domain of multifunction 9, 365IR, set of extended real numbers. 333o(z), cdf of standard normal distribution,epif, epigraph of function f, 333IIx, metric projection onto set X, 231epiconvergence, 377convergence in distribution, 163SN, the set of optimal solutions of the0(x,h)d order tangent set 348SAA problem. 156AVOR. Average value-at-Risk. 258Sa, the set of 8-optimal solutions of thef, set of probability measures, 306SAA problem. 181ID(A, B), deviation of set A from set Bn,N, optimal value of the Saa problem,334156IDIZ], dispersion measure of random vari-N(x), sample average function, 155able 7. 2541A(, characteristic function of set A, 334吧, expectation,361int(C), interior of set C, 336TH(A, B), Hausdorff distance between setsLa」, integer part of a∈R,219A and B. 334Isc f, lower semicontinuous hull of funcN, set of positive integers, 359tion f, 3332009/8/20pageList of notationsRc, radial cone to set C, 337C, tangent cone to set C, 337V-f(r), Hessian matrix of second orderpartial derivatives, 179a. subdifferential. 338a, Clarke generalized gradient, 336as, epsilon subdifferential, 380pos w, positive hull of matrix W, 29Pr(A), probability of event A, 360ri relative interior. 337upper semideviation, 255Le, lower semideviation, 255@R. Value-at-Risk. 25Var[X], variance of X, 149, optimal value of the true problem, 1565=(51,……,5), history of the process,{a,b},186r, conjugate of function/, 338f(x, d), generalized directional deriva-g(x, h), directional derivative, 334O,(, term, 382p-efficient point, 116lid, independently identically distributed,1562009/8/20page xlllPrefaceThe main topic of this book is optimization problems involving uncertain parametersfor which stochastic models are available. Although many ways have been proposed tomodel uncertain quantities stochastic models have proved their flexibility and usefulnessin diverse areas of science. This is mainly due to solid mathematical foundations andtheoretical richness of the theory of probabilitystochastic processes, and to soundstatistical techniques of using real dataOptimization problems involving stochastic models occur in almost all areas of scienceand engineering, from telecommunication and medicine to finance This stimulates interestin rigorous ways of formulating, analyzing, and solving such problems. Due to the presenceof random parameters in the model, the theory combines concepts of the optimization theory,the theory of probability and statistics, and functional analysis. Moreover, in recent years thetheory and methods of stochastic programming have undergone major advances. all thesefactors motivated us to present in an accessible and rigorous form contemporary models andideas of stochastic programming. We hope that the book will encourage other researchersto apply stochastic programming models and to undertake further studies of this fascinatinand rapidly developing areaWe do not try to provide a comprehensive presentation of all aspects of stochasticprogramming, but we rather concentrate on theoretical foundations and recent advances inselected areas. The book is organized into seven chapters The first chapter addresses modeling issues. The basic concepts, such as recourse actions, chance(probabilistic)constraintsand the nonanticipativity principle, are introduced in the context of specific models. Thediscussion is aimed at providing motivation for the theoretical developments in the book,rather than practical recommendationsChapters 2 and 3 present detailed development of the theory of two-stage and multistage stochastic programming problems. We analyze properties of the models and developoptimality conditions and duality theory in a rather general setting. Our analysis coversgeneral distributions of uncertain parameters and provides special results for discrete distributions, which are relevant for numerical methods. Due to specific properties of two- andmultistage stochastic programming problems, we were able to derive many of these resultswithout resorting to methods of functional analvsisThe basic assumption in the modeling and technical developments is that the proba-bility distribution of the random data is not influenced by our actions(decisions). In someapplications, this assumption could be unjustified. However, dependence of probability dis-tribution on decisions typically destroys the convex structure of the optimization problemsconsidered, and our analysis exploits convexity in a significant way
    2020-12-09下载
    积分:1
  • 遗传算法求最小值(matlab源代码和实验报告)
    遗传算法求最大值,遗传算法求最小值,实验报告,实验结果分析
    2020-11-28下载
    积分:1
  • IEEE14节点潮流计算
    电力系统潮流计算,IEEE14节点潮流计算程序;供学习电力系统潮流计算学者使用
    2020-11-30下载
    积分:1
  • ROS+VLAN25条ADSL 多线拔号
    ROS+VLAN25条ADSL 多线拔号ROS+VLAN25条ADSL 多线拔号ROS+VLAN25条ADSL 多线拔号
    2020-11-28下载
    积分:1
  • CST喇叭天线仿真
    CST喇叭天线仿真 CST是一款微波仿真软件
    2020-12-07下载
    积分:1
  • 696516资源总数
  • 106914会员总数
  • 0今日下载