Adhesive disbond detection of automotive components using first mode ultrasonic resonance

• Published in: NDT & E international : independent nondestructive testing and evaluation Vol. 36; no. 7; pp. 503 - 514
• Main Authors: Allin, J.M., Cawley, P., Lowe, M.J.S.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.10.2003; Elsevier Science
• Subjects: Analysing. Testing. Standards; Applied sciences; Cross-disciplinary physics: materials science; rheology; Dabber probe; Exact sciences and technology; Materials science; Materials testing; Metals. Metallurgy; NDT; Nondestructive testing; Nondestructive testing: ultrasonic testing, photoacoustic testing; Physics; Testing for defects; Ultrasonic resonance; Dabber probe; Ultrasonic resonance; NDT
• ISSN: 0963-8695; 1879-1174
• DOI: 10.1016/S0963-8695(03)00045-8

Adhesive bond inspection methods used in the aerospace industry are not suitable in the automotive industry, primarily owing to wide variations in adhesive thickness, and a requirement for couplant-free testing. This paper describes a robust technique for the detection of disbonds, based on the fundamental through-thickness resonance (mode 1) frequency of a joint. During testing, the mode 1 resonance is excited in the joint and the received signal is windowed, leaving the ringing of the first mode. If this resonance frequency falls into the range predicted for bonded joints based on the possible limits of adhesive thickness, then the bond integrity is confirmed; mode 1 resonance above the predicted frequency range indicates the joint is disbonded. Further investigation has shown that narrow beads of adhesive and tapered adhesive layers, which commonly occur in practice, do not affect the reliability of this technique. The development of a novel dry-contact dabber probe is also described, which comprises a low-loss rubber delay line with a highly attenuative rubber bonded to the side walls to eliminate side wall reflections. Results from prepared samples and automotive structures are then presented.