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1.
用激光超声评估复合材料   总被引:16,自引:0,他引:16       下载免费PDF全文
章肖融 《应用声学》2000,19(5):1-9,19
本文对应用激光超声方法检测金属基碳纤维增强复合材料,纳米陶瓷复合材料的声学和力学性质的进展,作了简要的介绍和讨论。  相似文献
2.
Longitudinal wave generation in laser ultrasonics   总被引:6,自引:0,他引:6  
3.
In the 1920s, the solid-solid interface wave, Stoneley wave, was first studied by Stoneley. From the 1930s to 1940s, the fluid-solid interface waves, usually called Scholte wave or Scholte-Stoneley wave, were studied by Cagniard and Scholte respec-tively[1]. The Scholte wave corresponds to the real root of the fluid-solid interface secu-lar equation, which is usually called the Scholte equation, and the velocity of Scholte wave is only slightly lower than the longitudinal velocity of the f…  相似文献
4.
固体中脉冲激光激发声表面波的理论研究   总被引:4,自引:0,他引:4       下载免费PDF全文
本文运用本征函数展开的方法对固体材料中脉冲激光激发的声表面波进行了理论研究,在考虑热弹激发的条件下,利用三维的轴对称模型,得到了脉冲激光光源的脉冲宽度以及聚焦半径对固体材料中声表面波信号的时域及频域的影响,对进行超短脉冲激光激发超声的研究具有指导意义。  相似文献
5.
王敬时  徐晓东  刘晓峻  许钢灿 《物理学报》2008,57(12):7765-7769
利用激光激发声表面波的理论模型,研究了被激发宽带声表面波在具有表面微裂纹缺陷金属材料上的传播特性.对具有不同形状的表面缺陷模型进行了数值分析.结果表明:表面微裂纹缺陷有明显的低通效应,缺陷深度越大高频截止频率就越低,缺陷深度与低通滤波的截止频率呈近似线性关系;缺陷的宽度增大对表面波透射能量有明显的衰减作用. 关键词: 激光超声 声表面波 有限元方法 低通滤波器  相似文献
6.
Silva MZ  Gouyon R  Lepoutre F 《Ultrasonics》2003,41(4):301-305
Preliminary results of hidden corrosion detection in aircraft aluminum structures using a noncontact laser based ultrasonic technique are presented. A short laser pulse focused to a line spot is used as a broadband source of ultrasonic guided waves in an aluminum 2024 sample cut from an aircraft structure and prepared with artificially corroded circular areas on its back surface. The out of plane surface displacements produced by the propagating ultrasonic waves were detected with a heterodyne Mach-Zehnder interferometer. Time-frequency analysis of the signals using a continuous wavelet transform allowed the identification of the generated Lamb modes by comparison with the calculated dispersion curves. The presence of back surface corrosion was detected by noting the loss of the S(1) mode near its cutoff frequency. This method is applicable to fast scanning inspection techniques and it is particularly suited for early corrosion detection.  相似文献
7.
Laser ultrasonics was applied to the manufacturing control of the integrity (no failure) of coated spherical particles designed for High Temperature Reactors (HTR). This control is of major importance, since the coating of the nuclear fuel kernel is designed to prevent from the diffusion of fission products outside the particle during reactor operation. The SiC layer composing the coating is particularly important, since this layer must be an impenetrable barrier for fission products. The integrity of the SiC shell (no crack within the shell) can be assessed by the ultrasonic vibration spectrum of the HTR particle, which is significantly changed, compared to the reference spectrum of a defect-free particle. Spheroidal vibration modes of defect-free dummy particles with a zirconium dioxide (ZrO2) core were observed in the 2-5 MHz range. A theoretical analysis is presented to account for the observed vibration spectra of defect-free or cracked HTR particles.  相似文献
8.
The interaction of surface acoustic waves generated by laser line source in the thermoelastic regime with surface notches are investigated. The finite element method is used to establish the model of the transient displacement field for surface notches with various depths and orientation. The magnitude of the signal enhancement in the near field and the mechanism by which this occurs are explained. The positions of notches were evaluated by the reflected Rayleigh wave. The depths and orientations of the notches were also determined using a shear wave that was generated through mode conversion of a surface acoustic wave at the notch tip. The results agree with previously published experimental measurements.  相似文献
9.
The generation of ultrasound in aluminum plate subjected to ring-shaped laser beam illumination has been studied quantitatively by using the finite element method. The superposition effects of surface acoustic waves on the top surface and the bulk ultrasonic waves on the rear surface of specimen have been obtained in a single simulation. The typical displacement profiles of the bulk ultrasonic wave at various depths along the central axis of the ring are obtained for three different radii, and the effect of the ring radius on the focal depths of the compression and shear mode are determined. The numerical results confirm that the focal depth of a bulk acoustic mode is determined by the directivity patterns of the acoustic mode generated by point-like laser sources via a thermoelastic mechanism, which depends on the physical constants of elastic medium.  相似文献
10.
激光在管道中激发周向导波的有限元模拟   总被引:1,自引:0,他引:1       下载免费PDF全文
赵艳  沈中华  陆建  倪晓武 《物理学报》2007,56(1):321-326
以超声的热弹激发机理为基础,建立了模拟激光在管道中激发周向导波的有限元模型.为了验证模型的正确性,根据Gao等人报道的实验条件[J. Appl. Phys. 91, 6114 (2002)]进行了模拟,理论模拟结果与Gao等人的实验结果符合很好,说明本数值模型的正确性.在此基础上,模拟激光在不同厚度、不同曲率半径的管道内激发的周向导波波形,同时分析了激光在管道中激发的周向导波波形与平板中激发Lamb波的差异,以及管道厚度和曲率半径对激光激发周向导波的影响.  相似文献
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