Challenges and New Developments for Air Coupled Ultrasonic Imaging

Hillger, Wolfgang; Dr. Hillger Ultrasonic-Techniques; Germany

Hillger, W.; Ingenieurbüro Dr. Hillger Ultrasonic-Techniques; Germany
Szewieczek, A.; Ingenieurbüro Dr. Hillger Ultrasonic-Techniques; Germany
Ilse, D.; Ingenieurbüro Dr. Hillger Ultrasonic-Techniques; Germany
Bühling, L.; Ingenieurbüro Dr. Hillger Ultrasonic-Techniques; Germany

ID: ECNDT-0102-2018
Download: PDF
Session: Aerospace 1
Room: G1
Date: 2018-06-12
Time: 10:50 - 11:10

Usually ultrasonic testing of complex aerospace components is carried out with squirter technique. However, water coupling delivers disadvantages like pressure variations, air-bubbles, lime scales, algae and corrosion of the mechanics. Therefore, a non-contact technique is preferable to avoid these disadvantages.
Problems caused by the large acoustic mismatch between solids and air are solved with special transducers, a powerful excitation as well as a hard- and software signal processing.

The testing is usually carried out in transmission technique with separate transducers on opposite sides of the component. The applications are mostly located in area of aerospace components such as sandwich components.

After 15 years of more or less laboratory applications the air-coupled ultrasonic technique (ACU) is used for large aerospace construction parts like the EC 145 tail boom and payload fairings. Because of the complex curved components robot scanners with 10 axes are necessary for the manipulation and the alignment of the transducers. The large component sizes require travelling lengths of 20 meters and more.

The new developments are focussed to eight channel systems with sender and receiver arrays. This reduces the time for scanning to 1/7 of the time for a one channel system. An ultra-low noise amplifier (ULNA) provides a 4 dB lower RMS value of noise than former types.

A further area of development is the ACU with one sided. Typical advantages of this technique is the reduction of scanning system complexity and the possibility to test hard accessible build-in components.