A novel acoustic NDT method using resonant air-coupled emission

Kreutzbruck, Marc; Institute für Kunststofftechnik - University of Stuttgart; Germany

Dillenz, A.; Edevis GmbH, Stuttgart; Germany
Kreutzbruck, M.; University of Stuttgart; Germany
Solodov, I.; University of Stuttgart; Germany

ID: ECNDT-0488-2018
Session: Air-couppled UT
Room: G2
Date: 2018-06-14
Time: 11:50 - 12:10

Resonant modes of non-destructive testing (NDT) which make use of local damage resonance
(LDR) have been developed recently and demonstrated a significant increase in efficiency and sensitivity
of hybrid inspection techniques by laser vibrometry, ultrasonic thermography, and shearography.
In this paper, a new fully acoustic version of resonant NDT is demonstrated for defects in
composite materials relevant to automotive and aviation applications. This technique is based on
an efficient activation of defect vibrations by using a sonic/ultrasonic wave matched to a fundamental
LDR frequency of the defect. On this condition, all points of the faulty area get involved in synchronous
out-of-plane vibrations which produce a similar in-phase wave motion in ambient air.
This effect of resonant air-coupled emission (RACE) results in airborne waves emanating from the defect
area, which can be received by a commercial microphone (low LDR frequency) or an air-coupled
ultrasonic transducer (high frequency LDR). A series of experiments confirm the feasibility of both
contact and non-contact versions of the technique for NDT and imaging of simulated and realistic
defects (impacts, delaminations, and disbonds) in composites.