基于等效载荷法, 应用有限元软件Abaqus模拟了脉冲激光激发的超声表面波在预加裂纹的半无限大弹性薄板内的传播, 并探讨了微裂纹的尺寸对超声信号的影响。将脉冲激光激励等效为作用在薄板表面的在时间和空间上均满足高斯分布的脉冲载荷, 并通过引入修正系数建立了激光的物理参数与峰值载荷的定量关系。在实验验证了有限元模型和等效载荷法正确性的基础上, 探讨了裂纹的宽度、深度对反射波和透射波声学特性的影响。结果表明,所建立的等效载荷法能有效地模拟激光超声检测裂纹的实验过程, 对激光超声的数值模拟研究以及在裂纹检测方面的应用具有重要的意义。

The ultrasonic surface wave induced by the laser shock processing and its propagation in half-space elastic plate with micro crack were simulated with Abaqus software based on equivalent load method, and the effects of the size of the micro cracks on the ultrasonic signal were also discussed. The pulsed laser was equivalent to a load with Gaussian profile in time and space, and the relationship between the physical parameters of the laser and the load was established by the correction factor. On the basis of verifying the correctness of the finite element model and equivalent load method, the effect of the crack width and depth on the acoustic characteristics of reflection wave and transmission wave was discussed. The results show that the equivalent load method is effective to simulate the process of laser ultrasonic crack detection, and it is very important for the numerical simulation of laser ultrasonic and the application in the detection of the crack.