表面窄缺陷深度的光声检测方法

Photoacoustic Detection Method for Depth of Surface Narrow Defects

为实现对表面缺陷深度的激光超声定量检测,建立了与缺陷宽度有关的深度测量理论。建立了含有宽度修正项的深度测量公式,并定义了缺陷尺寸比值概念,划分了窄缺陷、极窄缺陷与宽缺陷三种缺陷类型,以及在这三种不同类型下缺陷深度测量方法的适用性,并采用有限元仿真加以验证;搭建了激光超声检测实验平台,对铝合金表面缺陷样品进行了深度检测。结果表明:引入宽度修正项可实现对窄缺陷深度的定量检测,该方法的平均测量误差不足5%,很好地实现了缺陷深度的精确测量。

This paper develops a depth measurement theory related to defect width for the quantitative laser ultrasonic detection of surface defect depth. A depth measurement formula with a width correction item is established, and a concept of defect size ratio is defined. Defects are divided into three types, namely narrow defects, extremely narrow defects, and wide defects. The applicability of the defect depth measurement method in measuring the three types of defects is discussed, and finite element simulation is adopted for verification. Finally, an experimental platform for laser ultrasonic detection is built to conduct depth detection of aluminum alloy samples with surface defects. The results show that quantitative detection of narrow defect depth can be achieved by introducing the width correction item. The average measurement error is less than 5%, which means that accurate measurement of the defect depth has been achieved.