共查询到19条相似文献,搜索用时 798 毫秒
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为了激发粘接结构中的导波或界面波,通常需要将声波从两半无限介质同相位或反相位地同时入射多层系统。针对此问题,基于矩阵方法,推导了界面处于理想连接的情况下,对称或反对称纵波从上下半无限空间入射时,三层板状粘接结构中纵、横波的反射与透射系数表达式。分析了入射角度、粘接层厚度以及基体材料等对声波反射(或透射)特性的影响。结果表明,对称或反对称纵波垂直入射时不发生波型转换。粘接结构中声波的反射(或透射)特性与入射角度、频率以及粘接层厚度等参数密切相关。在相同的粘接层厚度(或频率)范围内,随着声波频率(或粘接层厚度)的增加,谐振频率曲线向低频漂移。该方法可作为粘接结构中体波或导波传播特性研究的重要理论基础。 相似文献
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利用波动理论的分析、处理方法,分析了偏心阻振质量阻抑振动波传递的特性,给出了偏心阻振质量对平面弯曲波传递的阻抑公式;相应的模型实验表明测试数据与理论推导结果趋势一致;并分析了阻振质量连接方式对其隔振性能的影响。借助数值仿真手段,将偏心阻振质量引入水下双壳动力舱段的减振降噪中。结果表明:阻振质量偏心布置时与其固定的船体板中发生波型变换,衍生波产生附加隔声量,且附加隔声量的量值主要取决于波型变换的程度;偏心阻振质量有效的抑制了双壳动力舱段中高频段的声辐射。 相似文献
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为了揭示周期结构中纵向波和弯曲波的耦合作用,设计了对称和非对称周期结构。考虑子结构中的纵向和弯曲耦合运动,利用导纳法和传递矩阵法,得到了周期单元的传递方程。由于结构中存在多种波的耦合作用,在求解周期单元的传播系数时将出现变态矩阵,采用波型分组法,求得了周期结构中多种波型的传播系数。推导了半无限长和有限长周期结构在纵向力、横向力和弯矩作用下的动态响应。数值计算结果表明,对称周期结构中纵向波和弯曲波的带隙结构相互独立;非对称周期结构中纵向波和弯曲波的耦合明显改变了两种波的带隙结构,只有在两种波阻带重叠的频段内结构上的振动响应才存在衰减。 相似文献
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预裂孔首先起爆形成贯通预裂缝对随后主爆孔爆破的振动频谱特征和能量分布产生重大影响。依托金沙江白鹤滩水电站左岸坝肩边坡开挖爆破试验,通过对预裂孔爆破和主爆破(主爆孔+缓冲孔)的振动信号进行小波包分析,获得预裂孔爆破和主爆破的功率谱和能量谱。通过对比发现:爆破振动的能量主要集中于40 Hz以内且分布极不均匀,存在多个主振频带。而在同一次爆破试验中,不同测点预裂孔爆破的主振频带比主爆破的主振频带分布更广,主爆破的主振频带集中于低频段,并且主爆破的能量和功率向低频的主振频带集中,反映出预裂孔爆破形成的预裂缝能很好地阻挡主爆破能量的传播,并存在高频滤波效应,频率较高、波长较短的振动应力波被预裂缝过滤,而频率较低、波长较长的应力波能更好地穿透预裂缝。试验结论对揭示预裂缝和对爆破振动传播及其频谱特征变化的影响具有参考价值。 相似文献
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典型船舶结构中振动波传递特性研究 总被引:4,自引:0,他引:4
摘要:以波动理论为基础,根据不均质结构中波型转换、阻抗特性,系统地分析了典型船舶结构中振动波的传递特性,推导并给出了平面弯曲波入射时的隔声量公式。在此基础上人为构造了阻抗失配基座,分析了阻抗失配基座的隔振性能。结果表明,十型结构对弯曲波有较强的阻抑作用,弯曲波在突变截面处的能量再分配关系主要由两块板的特性阻抗所决定;┻┳型构件的连接处机械阻力较大,其隔振效果超过十型结构; 型结构隔振性能随突变截面阻抗失配程度增大显著提高,采取多次截面突变的办法能够得到较大的隔声量;阻抗失配基座加剧了振动波在船体板架中的波型转换、散射和反射,使总的隔振效果显著提高。本文旨在为船舶结构声学设计提供参考。 相似文献
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Elastic wave and energy propagation in angled beams 总被引:1,自引:0,他引:1
This investigation comprises an experimental and numerical study of elastic wave propagation in angled beams. Axial impact by two strikers of different lengths was applied to three steel beams, each bent to incorporate a “V” section of different angle in the middle. Finite element simulation using ABAQUS was employed to examine details of the elastic waves generated in the impact tests. The numerical results correlated well with experimental data, and computational simulation was utilized to analyse the propagation of energy associated with the elastic waves. This demonstrated that after several reflections from and transmission across the bends energy is progressively smeared throughout the entire beam and does not concentrate at any particular segment; the bulk of the energy is conveyed via flexural waves. Numerical simulation of wave propagation in a beam with a single angle was also undertaken to study the energy associated with waves reflected from and transmitted across the bend, and how these are affected by the bend angle. The effects of input pulse duration, beam thickness and beam material properties on energy reflection and transmission at a bend are also discussed; this leads to the conclusion that when a longitudinal pulse of a particular frequency impinges on a bend, the ratio between its wavelength and the beam thickness governs the energy reflected from and transmitted across the bend. Moreover, the bend junction geometry (curvature) is found to have a significant influence on the energy reflected and transmitted, especially for obtuse bend angles. 相似文献
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Lateral displacement and its mechanism in asymmetric layered configuration are investigated. It is shown by the stationary-phase approach that displacements of both the transmitted and reflected beams can be positive as well as negative, and their magnitude can be greatly enhanced at transmission resonances. Numerical simulations show that for a well-collimated incident beam, if the norms of transmission and reflection coefficients are approximately constant within the peak of the angular-spectrum distribution of the beam, the transmitted and reflected beams can undergo lateral displacement without distortion, as long as the thickness of the layer satisfies a restriction. It is concluded that lateral displacement is not caused by beam distortion, but the result of reshaping the multiply transmitted (or reflected) beams. 相似文献
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Claudia E. Vanney 《Journal of Modern Optics》2013,60(4):685-700
Abstract A displacement of the transmitted wave for a uniaxial crystalisotropic medium interface is found, when the angle of incidence is larger than the limiting inhibited reflection angle. The phenomenon treated is a generalization of the well-known Goos—Hünchen effect [1] which is the longitudinal displacement of the reflected wave associated with total reflection in isotropic interfaces. Nevertheless, because of the crystal anisotropy, the displacement vector here has both a longitudinal and a transverse component even when the incident beam is linearly polarized. Expressions for these components are given and their meaning is analysed 相似文献
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Ouchani N Bria D Djafari-Rouhani B Nougaoui A 《Journal of the Optical Society of America. A, Optics, image science, and vision》2007,24(9):2710-2718
We show that by using a one-dimensional anisotropic photonic structure, it is possible to realize optical wave polarization conversion by reflection and transmission processes. Thus a single incident S(P) polarized plane wave can produce a single reflected P(S) polarized wave and a single transmitted P(S) polarized wave. This polarization conversion property can be fulfilled with a simple finite superlattice (SL) constituted of anisotropic dielectric materials. We discuss the appropriate choices of the material and geometrical properties to realize such structures. The transmission and reflection coefficients are calculated in the framework of the Green's function method. The amplitude and the polarization characteristics of reflected and transmitted waves are determined as functions of frequency, wave vector k(parallel) (parallel to the interface), and the orientations of the principal axes of the layers constituting the SL. Specific applications of these results are given for a SL consisting of alternating biaxial anisotropic layers NaNO(2)/SbSI sandwiched between two identical semi-infinite isotropic media. 相似文献
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Relations determining the laws of reflection and refraction of a plane wave in the defect field at an interface between two viscoplastic media are obtained based on the dynamic equations of the continuum theory of defects. The reflection and transmission coefficients relating the amplitudes of reflected and transmitted waves to the incident wave amplitude are determined. The obtained relations are applied to a particular case of media with weakly decaying waves. 相似文献
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舰船高传递损失基座振动波传递特性 总被引:2,自引:0,他引:2
基于波动理论,根据阻抗失配和波形转换原理,分析了不同基座连接结构中振动波传递特性,给出了隔振性能随基座板架厚度比及频率变化规律.接着讨论了阻振质量偏心布置对其隔振性能的影响,给出了偏心阻振质量对基座振动波传递的阻抑公式.在理论分析基础上,将高传递损失的基座连接结构延拓到基座面板、腹板和安装板架中,综合运用阻振质量以及贴... 相似文献
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针对钢轨弯曲波的传播及弯曲波反射后对钢轨振动特性测试的影响,对钢轨的弯曲波波速进行了理论推导,并设计了弯曲波波速测试试验,对弯曲波传播波速及其反射波的波速等特性进行了试验验证,同时就钢轨弯曲波对振动特性测试的影响及其解决措施进行了研究。结果表明:钢轨弯曲波的波速不是常数,而是频率的函数,弯曲波的不同频率分量以不同的波速传播,其弯曲波的反射波与入射波波速相同;在有限长的试验段内进行轨道结构振动特性测试时,不可忽略钢轨弯曲波的影响;在钢轨端部安装阻尼设备可有效抑制反射波对钢轨振动特性测试的影响。 相似文献