Spectral analysis of the scattering waveform of the laser-generated ultrasonic waves for detecting the crack in the material
-
摘要: 利用有限元法模拟了脉冲激光作用于单层铝板表面,由热弹机制产生超声波及其传播过程。针对相同厚度而含有不同深度的表面裂痕与给定埋藏深度的亚表面裂痕的单层铝板进行了对比计算,初步得到了声表面波经过表面裂痕及其亚表面裂痕时产生的反射及透射波形的特征;同时基于Wigner Ville分布的时间频率分析,得到了在裂痕前、后激光激发的瞬态表面波形的能量在时间频率平面内分布的情形,并就时频分析结果提出了不同深度的表面裂痕与亚表面裂痕对声表面波的声谱特征产生的显著影响,为激光超声的无损检测技术走向定量化提供了初步的理论依据。
-
关键词:
- 激光 /
- 有限元法 /
- 瑞利波 /
- Wigner Ville分布
Abstract: By means of the finite element method the laser-gener ated ultrasonic wave is simulated when laser interacts on the Al surface.After the resuts are computed for the Al plates with the same thickness but different depths of surface-breaking cracks and a given depth of subsuface crak under the top surface of the Al plate,the characteristics of the reflected wave and transmitted wave generated by the Rayleigh waves interacted with the surface breaking cracds and the subsurface crack are attained.Furthermore,based on Wingner-Vile theory the spectrum of the two signals recorded on both sides of the crack are a nalyzed.The result shows that the depths of the surface cracks and the subsurface crack cause the obvious effect on the spectral characteristics.This phenomena could be useful to the laser ultrasonic quantitative non-destructive evaluation (QNDE).-
Keywords:
- laser /
- finite element method /
- Rayleigh wave /
- Wig ner-Ville distribution
-
-
[1] 张淑仪.激光超声与材料无损评价 [J].应用声学,1992,11(4):1～6. [2] 张淑仪.超声无损检测高新技术 [J].国际学术动态,1998,8:58～60. [3] 章肖融.用激光超声评估复合材料 [J].应用声学,2000,19(5):1～9. [4] MCDONAL A F.On the precursor in laser-generated ultrasound waveforms in metals [J].A P L,1990,56:230～232.
[5] ROSE L R F.Point-source representation for laser-generated ultrasound [J].J Acoast Soc Amer,1984,75:723～732.
[6] CHENG J C,ZHANG S Y,WU L.Excitations of thermoelastic waves in plates by a pulsed laser [J].Appl Phys,1995,A61:311～319.
[7] CHENG J C,ZHANG S Y.Quantitative theory for laser-generated Lamb waves in orthotropic thin plates [J].A P L,1999,74:2087～2091.
[8] SHEN Z H,ZHANG S Y,CHENG J C.Theoretical study on SAW generated by laser pulse in solids [J].Analytical Science,2001,17:204～207.
[9] XU B Q,SHEN Z H,NI X W et al.Numerical simulation of laser-generated ultrasound by finite element method [J].J A P,2004,95(2):2116～2122.
[10] XU B Q,SHEN Z H,NI X W et al.Finite element models of laser-generated surface acoustic waves in coating-substrate system [J].J A P,2004,95(2):2109～2115.
[11] SHEN Z H,XU B Q,NI X W et al.Theoretical study on line source laser-induced surface acoustic waves in two-layer structure in ablative regime [J].Opt Laser Technol,2004,36:139～143.
[12] 袁易全,陈思忠,章肖融 et al.近代超声原理与应用[M].南京:南京大学出版社,1996.323～352. [13] NIETHAMMER M,JACOBS L J.Time-frequency representations ofLamb waves [J].J Acoust Soc Amer,2001,109(5):1841～1847.
[14] WU T T,CHEN Y Y.Wavelet analysis of laser-generated surfacewaves in a layered structure with unbond regions [J].Journal of Applied Mechanics,1999,66:507～513.
[15] 许伯强,倪晓武,沈中华 et al.激光激发板状材料中超声导波的有限元数值模拟 [J].中国激光,2004,31(5):621～625.
计量
- 文章访问数: 1
- HTML全文浏览量: 0
- PDF下载量: 6
下载: