Nondestructive evaluation of adhesively bonded joints using ultrasonic technique

Abstract

Quantitative nondestructive evaluation of defects is particularly important to ensure the reliability and safety of structures. The pulse-echo method is one of the most widely used ultrasonic techniques for evaluation of structural integrity In this study, ultrasonic signals were used to evaluate parameters related to attenuation and amplitude variation in adhesively bonded joints. Ultrasonic characteristics were measured in double cantilever beam (DCB) specimens under stress with mode I fracture. The FFT was used to determine bond-layer parameters such as effective thickness and frequency spectrum. A control experiment confirmed that the variation of frequency spectrum in the adhesive joints depends on the transition of stress variation. Furthermore, the adhesively bonded joint strength for DCB specimens was evaluated by the parameters of ultrasonic waves and the J-integral. The results reveal that the frequency analysis of ultrasonic waveform can be utilized as a tool for a nondestructive evaluation of adhesively bonded joints.