摘要
采用平面应变有限元法模拟了脉冲激光线源在含有表面微缺陷的铝板表面激发声表面波的物理过程,计算结果给出了激光线源逐渐靠近表面微缺陷时接收点得到的位移信号波形特征的显著变化规律;比较了不同深度的表面微缺陷对声表面波时域位移信号特征的定量影响;并在此基础上分析了紧随双极性R ay le igh波之后出现的振荡位移信号的时间间隔随表面缺陷深度增加而呈线性单调递增的趋势;同时证明不同的线光源半宽只会改变振荡信号的相对强度,而不会影响振荡信号的时间间隔;文中结果为利用声表面波位移信号中振荡成分的时间间隔来定量检测材料表面微缺陷深度提供了理论依据.
Plane strain finite element method has been employed in this paper to simulate the generation of the surface acoustic wave by the line focused pulsed laser irradiation on the aluminates plate with micro-surface breaking crack. The numerical results demonstrate that the characteristic changes of temporal waveforms are observed when the laser source is scanning close to a surface crack. The influence of the crack depths on the temporal waveforms of the surface acoustic waves has been studied in details, in which the temporal intervals of the oscillatory signals following the bipolar Rayleigh pulse are found to be proportional to the crack depths. Furthermore, the oscillatory signals generated on a defective sample by the line source with varied half-widths exhibit the identical temporal intervals. The crack depth related temporal interval of oscillatory signal can be used for crack depth gauging.
出处
《测试技术学报》
2010年第1期15-21,共7页
Journal of Test and Measurement Technology
基金
江苏省高校自然科学基金资助项目(09KJB140005)
南京邮电大学科研资助项目(NY207005)
关键词
激光超声
声表面波
有限元法
表面缺陷
laser ultrasonic
surface acoustic wave
finite element method
surface crack
