研究激光激发的声表面波与材料近表面缺陷的振荡效应

根据激光激发声表面波的热弹运动方程及热传导方程, 采取有限元技术对方程进行求解, 得到声表面波传播波形图. 当声表面波经过近表面缺陷时, 声表面波与近表面缺陷之间产生一种振荡效应, 通过近表面缺陷的振荡波形幅值存在一个逐渐增加后又逐渐减小的过程. 当声表面波经过不同深度的近表面缺陷时, 振荡信号中心频率存在一定的变化规律. 数值仿真结果表明: 当近表面缺陷深度从0.1 mm到0.5 mm变化时, 振荡效应产生的振荡信号中心频率从0.4 MHz到0.76 MHz变化, 振荡信号中心频率与近表面缺陷深度呈近似线性关系, 这为近表面缺陷的定量检测提供了一种理论基础.

Research on the oscillation effect of near-surface metal defect based on laser-generated acoustic surface wave

According to the thermoelastic equations and heat conduction equations of laser-generated acoustic surface wave (SAW), the SAW propagation images are obtained by taking finite element solutions to the equations. When the SAW propagates through the aluminum plate with the near-surface defects at different depths, producing an oscillating effect between the surface acoustic wave and the near-surface defects, and then there is a gradual decrease after the gradual decrease of the oscillation waves as getting through the near-surface defect. When the SAW propagates through the aluminum plate with the near-surface defect at different depth, there is a certain variation of the center frequency of the oscillation waves. Simulation results show that, when the depth of near-surface defect changes from 0.1 to 0.5 mm, the center frequency of the oscillation signal generated by the oscillation effect changes from 0.4 to 0.76 MHz, and the center frequency of the oscillation signal is seriously attenuated with increasing width of the near-surface defect, thus providing a theoretical basis for quantitative detection of the near-surface defects.