共查询到20条相似文献,搜索用时 62 毫秒
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剪切波相速度和衰减的频散特性的准确测量具有重要的意义。温度变化可能会对生物软组织的力学特性产生影响,为了研究温度的变化对剪切波相速度和衰减频散特性测量的影响,以大鼠肝脏为研究对象,基于声辐射力的剪切波成像的方法,通过离体实验来获取大鼠肝脏内部不同温度下的剪切波相速度和衰减频散特性曲线。实验结果发现,随着温度的升高,剪切波相速度逐渐减少,衰减频散逐渐增大,特别是在较高的频段(270~380 Hz)的变化更为显著。结果表明温度是测量大鼠肝脏中剪切波相速度和衰减频散特性中不可忽略的因素,这对今后的动物实验研究以及疾病评估提供了实验参考,具有重要的意义。 相似文献
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基于主动Lamb波的结构健康监测是目前复合材料结构损伤监测技术研究的热点之一,了解Lamb波的传播特性对进行可靠的损伤监测非常重要.本文结合经典三维弹性理论与Lamb波的运动位移方程,对碳纤维复合材料板中传播的Lamb波传播特性进行了建模研究,在此基础上推导了碳纤维板的相速度频散曲线,并讨论了Lamb波传播方向与坐标轴之间的夹角及碳纤维铺层方向对频散曲线的影响,建模结果证明了这种建模方法的正确性. 相似文献
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多层薄膜-基底结构在工业领域有广泛应用,其中薄膜的厚度与弹性参数等特性对结构与器件性能有显著影响。但对多层薄膜材料参数进行无损定征较为困难。考虑界面波对界面附近材料特性敏感的特点,以及分层薄膜导致液固界面Scholte波频散与分层材料速度分布密切相关等因素,文章首先利用全局矩阵理论分析了分层结构中的声传播,并给出界面上脉冲激励的声压表达式,据此对水浸双层薄膜-基底三层结构材料声速呈正梯度、负梯度、随机分布三种结构中液固界面Scholte波的频散曲线进行数值计算。进一步详细计算了法向脉冲线源激发的界面波瞬态信号随薄膜厚度的变化。结果显示,三种结构中两层薄膜厚度均对液-固界面波频散特性有显著影响,同时不同膜厚对不同频段的Scholte波的“捕获”作用(频率选择性)十分明显。该结果为进一步利用Scholte波频散特性进行多层薄膜厚度定征提供了理论依据。 相似文献
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各向异性成层地基中Rayleigh波的弥散特性 总被引:2,自引:0,他引:2
利用有限单元法及解析法推导了各向异性层地基中Rayleigh面波的弥散特征方程及各模态波位移分布的计算公式,可用于计算上软下硬地基,上硬下软地基及夹层地基Rayleiht面波的弥散曲线及位移分布。本文主要对各向异性上软下硬地基中Rayleigh面波弥散特性及位移分布规律进行了讨论。 相似文献
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饱和土层中Love波的传播特性 总被引:1,自引:0,他引:1
基于Biot的液体饱和孔隙介质模型,考虑孔隙流体粘性,导出了弹性半空间上饱和土层中Love波的复频散方程,然后将其转化为两个实方程并利用迭代的方法进行求解。讨论了Love波的波速范围、Love波的频散和衰减特性以及Love波的位移分布。 相似文献
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The propagation of shear-horizontal waves in a piezoelectric film of aluminum nitride on a silicon substrate is studied. Three different electrode configurations are considered for thin film acoustic wave resonator application. A theoretical analysis is performed. The equations of linear piezoelectricity and anisotropic elasticity are used for the film and the substrate, respectively. Real and imaginary dispersion curves as well as electromechanical mode shapes are obtained. The effects of electrode configuration on the distribution of the electromechanical fields and the dispersion curves of long thickness-twist waves as well as energy trapping are examined. 相似文献
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按照Lamb波理论,板内导波由多阶对称波和反对称波组成。当波长远大于板厚时,利用经典平板理论对Lamb方程进行简化,此时板内主要有零阶对称波S0和反对称波A0两种模态。认识薄板内声波模态,不仅有助于分析声源性质,提取有效信号,而且可以提高声发射检测中时差定位的准确性。利用PAC公司的Fieldcal标准信号发生器和Nielsen Hsu断铅法作为信号源在0.7 mm薄钢板上进行声波传播实验。通过比较实测波速和理论波速甄别板内的声波模态。实验发现对称波S0实测波速和理论波速比较吻合,而反对称波A0的波速由于频散而较难精确测量。综合两种模态波的波速情况,声发射检测中利用对称波速度进行声源定位计算更加接近薄壁结构声波的传播状况。 相似文献
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Dejin Huang 《先进材料力学与结构力学》2020,27(10):831-839
AbstractTwo-dimensional equations for flexural motions of a lithium niobate piezoelectric plate are derived from three-dimensional equations. The plate has a ferroelectric inversion layer where the piezoelectric constants reverse signs. The equations show an unconventional behavior that a uniform electric field along the plate thickness can produce bending. This offers many possibilities for new designs of devices. Waves in unbounded plates are examined for the accuracy of the equations. A piezoelectric energy harvester based on such a plate is analyzed as an example of the application of the equations derived in vibrations of finite plates. 相似文献
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Hydroelastic behaviour of compound floating plate in waves 总被引:3,自引:0,他引:3
The paper deals with the plane problem of the hydroelastic behaviour of floating plates under the influence of periodic surface water waves. Analysis of this problem is based on hydroelasticity, in which the coupled hydrodynamics and structural dynamics problems are solved simultaneously. The plate is modeled by an Euler beam. The method of numerical solution of the floating-beam problem is based on expansions of the hydrodynamic pressure and the beam deflection with respect to different basic functions. This makes it possible to simplify the treatment of the hydrodynamic part of the problem and at the same time to satisfy accurately the beam boundary conditions. Two approaches aimed to reduce the beam vibrations are described. In the first approach, an auxiliary floating plate is added to the main structure. The size of the auxiliary plate and its elastic characteristics can be chosen in such a way that deflections of the main structure for a given frequency of incident wave are reduced. Within the second approach the floating beam is connected to the sea bottom with a spring, the rigidity of which can be selected in such a way that deflections in the main part of the floating beam are very small. The effect of the vibration reduction is quite pronounced and can be utilized at the design stage. 相似文献
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文章对雷管输出的检测方法进行试验和探讨,包括铅板试验、声级测量、水下爆炸和小爆炸容器中冲击波的测量等。提出建立检测雷管爆炸冲击波标准方法的建议。 相似文献
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采用波动法研究有限尺寸加肋L型板结构的振动特性 总被引:1,自引:0,他引:1
本文采用波动方法研究有限尺寸加肋L型板结构的振动及其抑制问题。将有限尺寸方钢平板处理成平板结构弯曲和面内运动与方钢结构的弯扭运动和轴向运动的耦合连续模型,利用波动方法分析有限尺寸加肋L型板结构任意位置的动力学响应。数值结果表明,与有限元方法相比,波动法不仅可以准确地计算有限尺寸方钢平板结构的低频振动响应,而且能有效地计算其中高频振动响应。方钢布设在两板连接处,提高其抗扭刚度可提高减振效果;方钢布设于源板沿长度方向的三分之二位置处或靠近连接处的接受板上,具有较优的减振效果。 相似文献
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Bogumi? Wronka 《International Journal of Impact Engineering》2011,38(5):309-313
The basic defects occuring in explosive clad plates were properly systemized and the reasons of their formation were explained. Cases of cracks and delaminations in explosive clad plates were examined in this work. Various values of tensile stresses coming from loading and unloading waves were analysed, as they were the main reason of defects. The defects were connected with properties of welded materials in the joint area and beyond it. Some practical aspects of this process were shown as well. 相似文献