Ultrasonic characterization of bonding interfaces using Stoneley waves

An ultrasonic nondestructive method for evaluating bonding interface properties using Stoneley waves was proposed. First, a theoretical model was established. In this model, the dispersion relationship of the Stoneley wave at the quartz–steel interface and the transient signals generated by a pulse were analyzed. Significant differences were observed in the dispersion characteristics of Stoneley waves under different weak bonding conditions. Laser ultrasonic experiments were conducted to confirm the theoretical predictions, in which different interfacial strengths were simulated through the bonding–curing times. Based on these results, the inversion method was implemented to reconstruct the interfacial stiffness by using the corresponding dispersion of the Stoneley wave at different quartz–steel bonding interfaces extracted by the spectral analysis method. The results showed a similar tendency to those shown by theoretical predictions. Finally, the reconstructed interfacial stiffnesses were used to calculate the transient waveforms of the interface waves at different bonding–curing times, and the results showed good consistency with the experimental results, thereby verifying the rationality of the inversion results.