Multi-Body Dynamics Analysis and Low Noise Optimization of X6170ZC Diesel

Thelevel of vibration and noiseis animportant estima-tionindexoninternal combustionengines .As vibrationandnoise legislations are continually introduced and progres-sivelyrestricted,lowerlevel noise becomesincreasinglyim-portant .The traditional design pe…     

Identification of diesel front sound source based on continuous wavelet transform

Acoustic signals from diesel engines contain useful information but also include considerable noise components.To extract information for condition monitoring purposes, continuous wavelet transform (CWT) is used for the characterization of engine acoustics. This paper first reviews CWT characteristics represented by short duration transient signals.Wavelet selection and CWT are then implemented and wavelet transform is used to analyze the major sources of the engine front's exterior radiation sound. The research provides a reliable basis for engineering practice to reduce vehicle sound level.Comparison of the identification results of the measured acoustic signals with the identification results of the measured surface vibration showed good agreement.     

Identification of diesel front sound source based on continuous wavelet transform

Acoustic signals from diesel engines contain useful information but also include considerable noise components. To extract information for condition monitoring purposes, continuous wavelet transform (CWT) is used for the characterization of engine acoustics. This paper first reviews CWT characteristics represented by short duration transient signals. Wavelet selection and CWT are then implemented and wavelet transform is used to analyze the major sources of the engine front's exterior radiation sound. The research provides a reliable basis for engineering practice to reduce vehicle sound level. Comparison of the identification results of the measured acoustic signals with the identification results of the measured surface vibration showed good agreement.     

用不同方法进行发动机噪声源识别的研究

发动机噪声源识别对于制定发动机降噪措施十分重要 ,而像油底壳、气门罩、前齿轮室盖等罩壳类零件通常是发动机的主要噪声源 .本文用铅覆盖法和表面振动测量法对一台六缸工程机械用柴油机进行了表面噪声源识别的研究 ,得到了罩壳类零件按噪声能量大小的排列顺序 ,文中首先在半消声条件下利用铅覆盖技术测量了这些罩壳类零件的声功率 ,然后又研究了它们的振动特性 ,并通过表面振动速度的面积时间均方值预测了其声功率 .两种方法的测量结果吻合较好 ,说明了它们在工程领域应用的有效性     

基于ANSYS的压缩机机体动态特性研究

采用有限元方法对K5206NM压缩机机体进行了模态分析和振动响应分析,不仅获得了机体的固有频率和振型,还得出机体在动态工况下的位移、应力、速度及加速度变形云图,找到了机体结构的薄弱环节,并提出了相应的改进方案,为机体的结构设计改进提供理论依据.     

薄板结构振动声辐射特性分析及优化

利用有限元法与边界元法结合对薄板进行振动声辐射特性分析,研究了薄板结构在简谐力作用下表面声压分布状况,分析了不同边界条件、材料以及加筋形式等因素对薄板结构振动声辐射特性的影响,并对简支矩形薄板厚度进行了优化。研究表明,边界约束的增加会导致薄板刚度变大,进而导致薄板辐射声功率与辐射效率随之改变?不同材料对结构的辐射声功率均有影响,而对辐射效率影响很小?加筋对薄板声辐射特性影响显著,十字型加筋形式减震降噪效果最好?对薄板厚度进行优化,优化后薄板辐射声功率级下降了4.29dB。     

Dynamic response of functional virtual prototyping of motorcycle under combined excitations

This paper developed 3D product models of motorcycle and engine by UGNX as well as virtual prototyping by ADAMS program with road roughness generated by MATLAB. Under the straight-line running condition, the dynamic responses of motorcycle multibody system to both road and engine excitations were compared with those to only road excitation in terms of vertical acceleration response, amplitude frequency response and power spectral density. The comparisons of simulation data showed that the response due to flat road excitation was around 20 Hz, while that to the combined excitations was in a wide frequency band, of which the major components focused on 10 Hz, 15 Hz, 35 Hz ,70 Hz, 100 Hz and even higher frequencies, reflecting the characteristics of engine excitation based on its unbalanced inertia force and torque. It is concluded that the high fidelity virtual prototyping can simulate the dynamics of motorcycle product well in investigating the vibration and ride comfort performance.     

工程车辆驾驶室声学特性预测研究

建立某型工程车辆驾驶室的结构有限元模型、空腔声学有限元模型。对驾驶室结构和室内空腔声场进行模态分析,得到结构振动特性和声学特性。计算分析驾驶室声-结构耦合模型在特定频率激励下的噪声分布情况,同时考虑吸声材料对驾驶员耳旁声压级值的影响,总结出在新车型开发阶段进行车内噪声预测和控制研究的有效方法。     

韩山师院教学楼多功能厅建声环境的技术改造

厅堂扩声音质的优劣主要由建声、扩声等要素决定、合理选取混响时间，是音响系统工程成功的一半。本例对新建或改建厅堂的扩声音质设计有较高的实用参考价值。     

基于声腔模态分析的汽车低频噪声优化

根据汽车白车身结构有限元模型建立车身声固耦合模型。基于声学模态分析理论,进而求解声腔模态。通过实车怠速噪声和车身悬置激励力测试车内响应点的声压值,进一步验证声固耦合模型。通过峰值频率下的板块单元贡献量和模态应变能优化分析,汽车车内低频噪声降低,有利于提升汽车的NVH性能。     

基于NVH的车内声腔模态分析

根据某车室壁板结构有限元模型,建立了车室声腔有限元模型.基于声学模态分析理论,利用SYSNOISE软件对该声学有限元模型进行自由模态分析,获得了车室声腔的各阶固有频率和模态振型,并将声学模态分析结果与汽车的各种激励源频率特性进行分析比较,其结论可用来改进车身系统的声学设计.     

模态分析在车身声振设计中的应用

在模态分析的理论基础上,对模态分析在车身声振设计中的应用进行了探讨。通过实例分析了模态分析在车身声振设计中应用的基本方法、基本步骤,这为汽车振动和噪声的特性研究提供了有价值的参考依据。     

高校体育馆音响系统的设计

随着办学条件的不断改善,很多高校逐渐拥有了自已的体育场馆。由于高校体育馆是根据自己的需要设计的,所以在音响系统的设计时应依据其自身特点和需求来进行,音响系统的设计要考虑以下三个要素:体育馆的建筑声学条件、音响的功率和扬声器的布局。     

火炉子沟大桥动力特性分析

用有限元计算桥梁结构的前几阶固有频率和振型等模态参数,在此基础上进行现场动态测试,将动测信号进行频谱分析,可识别出桥梁结构的固有频率等参数.综合分析表明,该桥梁结构动力特性的计算值与动测识别值两者是一致的,因此,该大桥动力特性达到了设计要求.这种计算和现场测试相结合的方法,能可靠得到桥梁结构的动力特性,借此,可检验大桥的施工质量和确定大桥的实际承载能力.     

防滑差速器壳体的模态仿真与试验研究

为了获取某四驱汽车防滑差速器壳体的固有振动特性和验证所建有限元模型的正确性,以某四驱汽车防滑差速器壳体为研究对象,首先基于Abaqus软件对其进行模态仿真分析,得到了防滑差速器前6阶固有特性参数及其振型;然后运用锤击实验对防滑差速器进行模态分析实验,测取其振动情况;最后将两种方法获取的差速器壳体前6阶振型及振动频率进行对比。结果发现两种方法获取的各阶振型基本一致,固有频率误差在5%以内。这种以模态仿真分析为前提,模态实验为补充,仿真结果与实验结果相对比的分析方法有效地验证了有限元模型的正确性,为防滑差速器的有限元分析提供了有效的参考依据。     

提高多媒体教室音质与图像清晰度的探讨

多媒体教室的音质与图像清晰度,直接影响着教学信息的传递和教学的质量。如何获得理想的听音效果,既能保证语言的清晰度,又能保证音乐、效果声的保真度;如何最大限度地提高图像清晰度。文章从声学设计、音响系统设计与配接、视频系统的选型与配接等方面进行了探讨。     

立体组装电路模块动态特性的有限元模拟与分析

Based on the modal analysis theory and by using the dynamics finite element analysis model of a three-dimensional assembly circuit module, dynamic characteristics of circuit module have been studied, including both natural characteristics analysis and dynamic responses analysis. Using a subspace method, modal analysis is first carried out. The first 6 orders of natural frequencies and vibration modes are obtained. Influence of the number of the Z-shaped metal slices on dynamic characteristics of the entire structure is also studied.Harmonic response analysis is then conducted. The steady-state response when the circuit module is subjected to harmonic excitation is determined. A curve of the response values against frequencies is obtained. As a result, the optimal number of Z-shaped metal slices can be determined, and it can be assured that the three-dimensional assembly circuit module has good performance in terms of the dynamic characteristics.     

双层等厚筛性能研究及振动参数优化

为研究振动参数对双层等厚筛筛分效率的影响,采用离散单元法(DEM)模拟5种不同粒径的颗粒在不同振幅、筛面倾角、振动频率下的筛分过程。运用多项式逼近方法对仿真结果进行曲线拟合,得到拟合度最好时的筛分效率与振动参数关系图。最后,选出最好筛分效率下的振动参数进行正交试验。结果表明:双层等厚筛筛分效率最优的参数组合为振动幅度7mm、振动频率14Hz、筛面倾角17°。     

Diagnosis of valve-slap of diesel engine with EEMD-EMD-AGST approach

A hybrid of ensemble empirical mode decomposition and empirical mode decomposition (EEMD-EMD) is introduced to diagnose the valve-slap vibration signal,which is relative to the dominant combustion knock vibration signal given out by a diesel engine around the top dead center (TDC).The time-frequency representations of intrinsic mode functions (IMFs) decomposed by EEMD-EMD are obtained by adaptive generalized S transform (AGST).A type 493 diesel engine was used for the experiment,and the result indicates that the valve-slap of the diesel engine is serious,and the vibration frequencies are higher than the combustion knock.With EEMD-EMD-AGST approach,the valve-slap can be identified by the vibration analysis of the diesel engine.     

宽带波导吸振器吸振性能研究

为了满足对声频振动控制的要求,拓宽动力吸振器的吸振频率范围,本文在对直梁宽频带动力吸振器研究的基础上,研究了螺旋曲梁式动力吸振器.研究表明,该吸振器具有更密集的模态,因而具有宽频带的吸振性能.它的变截面形式使得它具有更强的消耗振动能量的能力,数值分析还表明如果设计合理,在0～1000Hz的频率范围内都可以获得较大的吸振量,有望成为噪声与振动控制新的有效手段.