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为了研究激光激发表面波与亚表面缺陷的作用机理,实现激光超声技术对该类型缺陷的定量检测,论文基于激光超声热弹机制,采用有限元方法模拟了激光激发表面波与亚表面矩形缺陷之间的相互作用,进而探讨缺陷的埋藏深度及其纵向尺寸对表面波的影响.首先模拟了激光激发表面波与矩形缺陷前沿(波与缺陷最先作用的纵向边沿)的相互作用,分析了埋藏深度对波形的影响,提取了缺陷作用的散射回波特征并分析其成因.然后对一定的缺陷埋藏深度,通过改变缺陷纵向尺寸,计算和分析了纵向尺寸对散射回波特征的影响.研究结果表明,散射回波的特征点到达时间与缺陷的埋藏深度和纵向尺寸有关,可能由此实现其反问题缺陷纵向尺寸的估算.
In order to study the mechanism of laser-induced SAW and subsurface defects, and realize the quantitative detection of this type of defect by using laser ultrasonic technique, a finite element method was used to simulate the laser-induced surface wave and subsurface rectangle defects The interaction between laser induced surface wave and the front edge of rectangular defect (the first edge of the wave and the defect) is simulated and the effects of buried depth and vertical dimension of the buried surface Depth of the waveform, extracted the characteristics of the scattering echoes of defects and analyzed its causes.And then, for a certain depth of buried defects, by changing the vertical size of the defects, the influence of the vertical dimension on the characteristics of the scattered echoes was calculated and analyzed.The results It shows that the arrival times of the characteristic points of the scattered echoes are related to the depth and vertical size of the defects, which may lead to the estimation of the vertical dimension of the inverse problem defects.