Ultrasonic Propagation Characteristics Of Double-layer Bonding Structure And Detection Of Interfacial Bonding Quality

Due to the high specific strength and specific modulus,excellent shock absorption performance and simple manufacture technology,the bonding structure is widely applied in important fields like aviation,aerospace,military industry and so on.Bonding failure caused by low bonding strength is the main cause of frequent occurrence of bonding structure accidents.To judge the bonding strength of the bonding structure by the Interfacial Bonding Quality,this article did the following work:Based on the basic theory of sound waves and the(Quasi-Static Model)QSM model,a mathematical model of ultrasonic propagation in the two-layer bonding structure is established.Numerical simulation results show: The number of transmission peaks increases after the thickness of the medium increases.When the adhesive body changes from "soft" to "hard",the transmission coefficient decreases.After increasing the interface stiffness coefficient,the transmission coefficient increases,and the increase speed is fast and then slow.The transmission peak frequency moves to high-frequency with the increase of stiffness coefficient,and the phenomenon of "peak drift" occurs.According to the characteristics of acoustic wave propagation,a mathematical model of acoustic detection based on time delay spectrum is established by spring model.The delay time of no thin layer,0.3mm,0.6mm,0.9mm resin thin layer under different interface stiffness coefficients is studied.The simulation results show that: As the interfacial stiffness increases,the peak delay time gradually decreases.The peak resonance frequency is only related to the thickness of the thin layer.The larger the thickness,the longer the peak delay time and the smaller the resonance frequency.Comparing the simulation and experimental results,the peak delay time error of the 0.3mm thick layer is 17% at maximum,and the 0.6mm and 0.9mm are within 5%.An ultrasonic detecting device is designed to simulate IBQ change by adjusting the pressure.Ultrasonic testing by transmission method shows that: As the pressure rises,the transmission energy increases,it changes faster and slower and decreases with the increase of the central frequency of the transducer.The frequency of transmission peak drifts to high frequency with the increase of pressure,and is related to the thickness of medium and the position of peak.The transmission peak drift distance is affected by the thickness of the double-layer plate and the center frequency of the detection transducer.