激光激发声表面波在缺陷板材中散射过程的有限元分析

利用有限元法模拟了金属板材中激光激发的声表面波经过缺陷位置时发生散射的瞬态过程，采用线状激光源作为超声导波的激发源.针对三种不同深度的表面缺陷以及三种亚表面缺陷的模型进行了对比计算，结果显示缺陷的深度及位置对声表面波的时域特征存在显著的影响.表面缺陷深度越深将产生较大幅度的表面反射回波，亚表面缺陷的影响将取决于缺陷上顶面距离板材上表面的距离.因此，数值模拟结果表明通过分析激光产生的表面波形可以判定近表面缺陷的尺寸和所处的位置.

Finite Element Analysis of Laser-Generated Rayleigh Wave Scattering by Cracks in a Plate

The finite element method has been utilized to investigate the transient scattering of Rayleigh wave by a crack on a plate. The incident wave models and the guided waves generated by a pulsed line source are laser irradiation on the plate. Three surface-breaking cracks and three subsurface cracks are studied here. The results show that the location and the depth of cracks have measurable effects on the surface responses in time domains. The deeper surface-breaking crack will generate the more amplitude reflected wave, and the effect of the subsurface crack attributes to the vertical distance from the tip of subsurface crack to the top surface of the plate. Therefore,the waveform can be used to detect the surface breaking crack dimensions and the location position of the subsurface crack.