激光照射金属圆柱表面激发出的声表面波,在沿圆柱表面传播过程中产生色散和相移,并在表面缺陷前沿处幅值会有显著增强的现象,为表面缺陷的检测提供了新途径。基于激光激发的声表面波这一现象,提出通过扫描检测点的方法确定缺陷的位置,给出了表面波在表面缺陷附近的传播路径和缺陷深度计算公式。数值研究表明:(1)相对于脉冲回波法,扫查检测点方法提高了缺陷检测的位置精度,有效减小了圆柱表面波传播过程的色散和频移现象对缺陷位置精度的影响。(2)当缺陷深度范围为1~2 mm,通过给出的缺陷深度计算公式得到仿真缺陷深度与实际缺陷深度之间的误差控制在6 %以内,验证了提出的缺陷深度计算公式的有效性。以上研究结果为应用表面波检测圆柱类零件表面缺陷提供了有价值的参考。
The surface acoustic wave excited by the laser irradiating the surface of the metal cylinder generates dispersion and phase shift during the propagation along the surface of the cylinder,and the amplitude at the front edge of the surface defect is significantly enhanced,which provides a new way for the detection of surface defects. Based on the phenomenon of surface acoustic wave excited by laser,it is proposed to determine the position of the defect by scanning the detection point,and the formula of calculating the depth of surface defect and the propagation path near the surface defect are given. Numerical research show that:(1) Compared with the pulse echo method,the scanning detection point method improves the position accuracy of the detection of defect,and effectively reduces the influence of the dispersion and frequency shift phenomenon on the position accuracy of surface defects. (2) When the defect depth range is 1~2 mm,the error between the simulated defect depth and the actual defect depth is controlled within 6 % by the given formula of calculating defect depth,and the validity of the proposed formula of calculating defect depth is verified. The above research results provide a valuable reference for applying the surface wave to detect surface defects of cylindrical parts.
XU Zhi-xiang,YANG Fan,GUAN Shou-yan,LI Lian-fu.Research on detection method of cylindrical surface defect based on laser ultrasonic surface wave enhancement effect[J].LASER & INFRARED,2020,50(10):1183~1189