COMSOL Multiphysics仿真软件数值模拟了激光线源热弹激发超声波的物理过程, 进行了理论分析和实验验证, 阐述了激光超声的激发原理, 给出了时间步长及空间步长的选取原则。基于有限元方法建立了二维平面应变模型, 通过求解计算得到了激光热弹激发出声波的传播规律和缺陷回波, 并对其进行了时域分析。结果表明, 当缺陷大小、检测点保持不变的情况下, 缺陷位置距离入射点越远, 接收到回波的时间越长, 并且有一定的衰减; 当检测点、缺陷位置保持不变的情况下, 当缺陷深度为0.05 mm时, 就能够接受到缺陷回波信号, 在一定范围内缺陷回波振幅随着表面缺陷的加深而增加, 当缺陷深度为0.4 mm之后, 缺陷回波的振幅趋于稳定。

Numerical value of COMSOL Multiphysics simulation software is used in this articleto simulate the physical process of laser line source thermoelastic generation of ultrasonic waves. Theoretical analysis and experimental verification are contained and excitation principle of laser ultrasound is explained. The principle of selecting time step and space step is given. A two-dimensional plane strain model is established based on FEA, the propagation law and defect echo of the acoustic wave excited by the laser line source thermoelastic are obtained by calculation, and the time domain analysis is carried out. The results show that when the defect size and the detection point remain unchanged, the farther the defect position is from the incident point, the longer the echo is received, and attenuation is there; if the position of detection point and defect position remain unchanged, when the depth of the defect is 0.05 mm, the defect echo signal can be received. And the amplitude of the defect echo increases with the deepening of the surface defect within a certain range, when the depth of the defect reaches to 0.4 mm, the amplitude of the defect echo tends to be stable.