共查询到20条相似文献,搜索用时 15 毫秒
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穿孔管消声器消声性能的有限元计算及分析 总被引:7,自引:0,他引:7
使用有限元法计算穿孔管消声器的传递损失,并与实验测量结果进行了比较,二者吻合良好。穿孔率 相同而孔径不同的两个穿孔管消声器的传递损失与具有相同直径和长度的简单膨胀腔消声器的传递损失比较表 明,穿孔管对消声器的低频性能影响较小,而对中频消声性能影响很大、对高频消声性能影响有限。 相似文献
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W. H. Prosser M. A. Hamstad J. Gary A. O'Gallagher 《Journal of Nondestructive Evaluation》1999,18(3):83-90
A comparison was made between two approaches to predict acoustic emission waveforms in thin plates. A normal mode solution method for Mindlin plate theory was used to predict the response of the flexural plate mode to a point source, step-function load, applied on the plate surface. The second approach used a dynamic finite element method to model the problem using equations of motion based on exact linear elasticity. Calculations were made using properties for both isotropic (aluminum) and anisotropic (unidirectional graphite/epoxy composite) materials. For simulations of anisotropic plates, propagation along multiple directions was evaluated. In general, agreement between the two theoretical approaches was good. Discrepancies in the waveforms at longer times were caused by differences in reflections from the lateral plate boundaries. These differences resulted from the fact that the two methods used different boundary conditions. At shorter times in the signals, before reflections, the slight discrepancies in the waveforms were attributed to limitations of Mindlin plate theory, which is an approximate plate theory. The advantages of the finite element method are that it used the exact linear elasticity solutions, and that it can be used to model real source conditions and complicated, finite specimen geometries as well as thick plates. These advantages come at a cost of increased computational difficulty, requiring lengthy calculations on workstations or supercomputers. The Mindlin plate theory solutions, meanwhile, can be quickly generated on personal computers. Specimens with finite geometry can also be modeled. However, only limited simple geometries such as circular or rectangular plates can easily be accommodated with the normal mode solution technique. Likewise, very limited source configurations can be modeled and plate theory is applicable only to thin plates. 相似文献
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声场中倏逝波特性及改进全息重建方法的研究 总被引:1,自引:0,他引:1
近场声全息是通过在紧靠被测声源物体的近场测量面上记录全息数据,不但可以记录传播波成分,还可以获得反映声场高空间特性的倏逝波成分。通过分析传播波和倏逝波在声场中的分布情况与声场空间位置、声源大小及频率的关系,得出了传播波和倏逝波在空间声场中的变化规律、影响因素以及二者之间的对应关系。通过对不同背景噪声下倏逝波的传播情况确定了可利用倏逝波传播距离。在此基础上,提出了一种改进的声全息方法,通过用这种方法,可得出声源面上传播波与倏逝波成分,获取等效于近场声全息的重建结果。最后,通过仿真验证了这一结果。 相似文献
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Transmissive Labyrinthine Acoustic Metamaterial-Based Holography for Extraordinary Energy Harvesting
Shubhi Bansal Christabel Choi James Hardwick Biswajoy Bagchi Manish K. Tiwari Sriram Subramanian 《Advanced Engineering Materials》2023,25(4):2370017
Conventional energy sources are continuously depleting, and the world is actively seeking new green and efficient energy solutions. Enormous amounts of acoustic energy are dissipated daily, but the low intensity and limited efficiency of current harvesting techniques are preventing its adoption as a ubiquitous method of power generation. Herein, a strategic solution to increase acoustic energy harvesting efficiency using a specially designed metamaterial is implemented. A scalable transmissive labyrinthine acoustic metamaterial (LAM) is designed, developed, and employed to maximize ultrasound (40 kHz) capture over its large surface area (>27 k mm2), which is focused onto a piezoelectric film (78.6 mm2), thus magnifying incident sound pressure by 13.6 times. Three different piezoelectric films – two commercial and one lab-made nanocomposite film are tested with LAM in the acoustic energy harvesting system. An extraordinary voltage gain of 157–173% and a maximum power gain of 272% using the LAM compared to the case without the LAM are achieved. Multipoint focusing using holographic techniques, showcasing acoustic patterning to allow on-demand simultaneous harvesting in separate locations, is demonstrated. Our versatile approach for high-intensity acoustic energy harvesting opens future opportunities to exploit sound energy as a resource to contribute toward global sustainability. 相似文献
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管束的流体弹性不稳定性的研究 总被引:2,自引:0,他引:2
基于Lever与Weaver的“流管”模型,本文对换热器管束的流体弹性不稳定性进行了较深入的研究。认为管子作周期性的衰减(或发散)运动。基本方程以复数形式表示,并用复数解法来求解。证明了作用在管上的流体力与管子运动时的位移、速度、加速度密切相关。作出的稳定区图可用来判断管子是否发生流体弹性不稳定现象。将节径比为1.25,1.32与1.41的正方形排列的管束,依次放入风洞中进行试验,取得了令人满意的结果。 相似文献
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用整体划分单元法建立了一种四节点20个自由度自由阻尼处理薄板结构的有限元模型,用能量法推导了单元的刚度和质量矩阵。在用有限元法计算结构的动态响应特性的基础上,将每个单元划分为很多个微元,利用有限元分析得到结构表面振动速度,通过单元的形函数,求出微元上几个点的平均速度,作为微元的振动速度。以每个微元为一单位,分别计算声压和声功率之后叠加起来,即得整个结构的声辐射。算例表明,用此方法分析计算表面阻尼处理结构的动态特性和声辐射是可行的。 相似文献
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单频悬臂梁式压电振动能量采集器存在工作频带窄、采集转换效率低等问题。通过在单频悬臂梁式压电振动能量采集器的水平悬臂梁末端增加一垂直悬臂梁,构造了一种L型宽频压电振动能量采集器;运用有限元法建立L型振动能量采集器的有限元分析模型,仿真分析了L型振动能量采集器的结构参数对其前两阶模态频率的影响,得到了结构最优尺寸。利用Hamilton原理建立了L型能量采集器的机电耦合分析模型,对其振动特性和电输出特性进行了数值仿真,结果表明L型结构能够提高能量采集器的工作频带和采集效率。 相似文献
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目的研究直径Φ20 mm、壁厚2 mm的5A06铝合金管在单向拉伸试验下的表现以及其在外支承球形缩口成形中的变形特点。方法利用管材准静态单向拉伸试验测试其力学性能,获得真实应力-应变曲线,再结合有限元软件ABAQUS分析管缩口成形的应力应变特征。结果 5A06管在拉伸中表现出良好的应变硬化能力,并呈明显的锯齿波动屈服特性。模拟结果显示缩口中的管坯整体处于周向、轴向压应力状态;主变形区内,轴向应变从缩口口边的拉应变逐渐变为主变形区向直壁过渡区域的压应变;除主变形区外,直壁部分的壁厚也有所增加。Φ20 mm×2 mm的5A06管在模拟中的极限缩口系数约为0.410。结论Φ20 mm×2 mm的5A06管在外支承球形缩口中的模拟成形极限较高,有限元分析作为缩口成形模具和工艺设计的前一步工作,其结果有一定的参考价值。 相似文献
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基于周期台阶表面声阻抗理论,解释了"水鸣天梯"声景观的物理机制。首先在低频准平面波近似的情况下,利用阻抗转移公式得到了周期台阶单元表面声阻抗。数值解表明,在低频段台阶表面的声阻抗呈现纯容抗性,证实了表面波的存在。有限元软件仿真的结果与理论分析保持一致。应用表面波的性质,设计并进行了现场试验。试验数据分析表明:在台阶底部脚踏石阶或者发射脉冲声波,声波经过台阶表面作用,到达台阶顶部时只有低频部分的声能量得到了较大保留,与理论分析和模拟结果相一致,最终确定了正是周期台阶的表面波滤波效应使得脚踏声转变为悦耳的水滴声。 相似文献