斜入射激光超声体波声场的实验研究

为研究微烧蚀状态下圆形光斑斜入射时激光超声声场的指向性,使用脉冲激光辐照半圆柱形铝质工件表面,并使用压电探头和电磁超声探头分别接收纵波和横波信号。根据速度参数确定了超声信号的类型,提取了信号的峰-峰值,并绘制出声场指向性曲线。通过分析获得以下结论:激光斜入射角度在0~60°范围内变化时,纵波声场的声束轴线方向保持不变,且与工件内法线平行;另外,横波声场的峰-峰值仍然在±35°的方向上取最大值,但是横波指向图形的主瓣易受激光入射方向的影响,当倾斜角度大于等于45°时,横波主瓣的范围变得较宽。

Experimental study on ultrasonic bulk field induced by oblique laser

The directivity patterns of the ultrasonic field induced by an oblique laser are investigated. The longitudinal wave and shear wave are respectively received by a piezoelectric transducer and an electromagnetic acoustic transducer in a state of micro ablation. At first, according to the ultrasound speeds, the signal types are determined. Then the directivity patterns are obtained by drawing peak to peak curve in the polar coordinate. The directivity patterns with normal axis of longitudinal wave do not change obviously for incidence angles in the range of 0-60, and angles for the maximum amplitude of shear wave still remain at 35 and -35. However, the main lobe of the directivity patterns for shear wave is sensitive to the incidence angle. In another word, shear wave amplitude near the normal increases with the incidence angle, especially when the inclined angle is no less than 45.