激光超声在缺陷材料中散射波形的声谱分析  

Spectral analysis of the scattering waveform of the laser-generated ultrasonic waves for detecting the crack in the material

作　　者：关建飞[1] 沈中华[1] 许伯强[1] 陆建[1] 倪晓武[1] 

机构地区：[1]南京理工大学信息物理与工程系,南京210094

出　　处：《激光技术》2005年第3期287-290,314,共5页Laser Technology

基　　金：国家自然科学基金资助项目(60208004);江苏省自然科学基金资助项目(BK2001056)

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WignerVille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。By means of the finite element method the laser-gener ated ultrasonic wave is simulated when laser interacts on the Al surface.After t he resuts are computed for the Al plates with the same thickness but different d epths 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 transm itted 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 subsurfac e crack cause the obvious effect on the spectral characteristics.This phenomena could be useful to the laser ultrasonic quantitative non-destructive evaluation (QNDE).

关 键 词：激光 有限元法 瑞利波 Wigner—Ville分布 

分 类 号：TN249[电子电信—物理电子学] O426[理学—声学]