线状烧蚀光源作用时瑞利表面波的指向性研究

摘要

针对线状激光光斑烧蚀工件表面的情况，利用理论分析和实验验证的方法研究了激光超声瑞利表面波的指向性。基于激光超声的烧蚀机理，将激光的烧蚀作用等效于法向应力，研究了线状垂直力源作用下远场质点的位移，提出了瑞利表面波的指向性公式。搭建了一套激光超声瑞利表面波激发与接收的系统，对获得的信号进行了幅频特性分析，以便验证信号中心频率与换能器中心频率的对应性。利用信号的峰峰值获得瑞利表面波指向性数据的实验值，并对指向性公式进行了验证。结果表明，该指向性公式对于瑞利表面波检测具有一定的参考价值。%When the surface of a specimen is ablated by a linear laser source,the directivity of laser ultrasound Ray-leigh surface wave is studied.Based on the ablation mechanism of laser ultrasound,laser ablation is regarded as a nor-mal stress.According to the displacement of a particle in the far field,the directivity function of Rayleigh surface wave is given.A set of laser ultrasound transmitting and receiving system was built,and the amplitude -frequency charac-teristics of the obtained signals were analyzed to verify the correspondence of signal center frequency and transducer center frequency.The directivity pattern corresponding angles were drawn in the polar coordinate system by using peak to peak value,and then the factors affecting the measurements of directivity patterns are discussed.The results show that the directivity function has a reference value for laser ultrasonic testing and inspection by using Rayleigh surface wave.