Study On Extraction Of Excitation And Waveform Parameters Excited By Laser In Bonding Defective Structure Materials

Bonding material is an important way to realize product’s simple assembly and characteristics improving. It has been widely used in the field of modern industrial manufacture. The bonding defects of different forms hidden within the bonding material which are introduced during the process of bonding can not be found easily. And they affect the product’s performance directly. Therefore, the development of non-contact nondestructive testing technology in bonding material has important practical significance.On the basis of in-depth information research, we introduced the idea about laser ultrasonic testing of hidden defects in bonding structure material. In theory, the physical model of the laser exciting ultrasonic in the material has been given. And on this basis, we wrote the finite element simulation program of the laser exciting ultrasonic in the structure material. Through a large number of finite element simulation experiments, the spatial distribution of the laser exciting ultrasonic in the quartz-tungsten bonding materials containing different defects have been obtained. They showed the influence of the defects on the laser ultrasonic distribution intuitively. On this basis, we discussed the influence of the defects’width, depth and other parameters on the laser ultrasonic defect signal. This paper also introduced the maximum entropy spectrum analysis method to estimate the center frequency deviation of the laser ultrasonic defect signal. And then we obtained the depth parameter of bonding defect by inversion. The paper introduced the Fourier spectrum analysis method to extract the attenuation coefficient in the frequency domain of laser ultrasonic signal and the energy of defect signal. And then we obtained the depth parameter of bonding defect by inversion. Also, we obtained the time-frequency signal by wavelet analysis and then got the depth parameter of bonding defect by inversion. Verified by finite element simulation experiments, the inversion of defects’depth parameters by the above methods and theoretical simulation experimental parameters have good consistency. But in comparison, the defects’ depth parameter inverted by wavelet analysis method is most accurate.This thesis research work for the laser ultrasonic detection technology applied to the hidden defects in bonding structure materials testing has certain reference value.