Center Smart Materials and Adaptive Systems CeSMA
Center Smart Materials and Adaptive Systems CeSMA

Large-scale structural health monitoring with ultrasound

© Fraunhofer ISC
Transducer element in glass solder on steel tube.

The monitoring of safety-relevant load-bearing structures of glass facades, steel pipes, and fiber composite components in vehicles and aircrafts, wind turbines requires long-term stable sensors with high error and spatial resolution. With the help of integrable piezoelectric ultrasonic transducers, ultrasonic pulses in the frequency range 20 - 200 kHz are coupled into the component. A comparison with the original reference image results in deviations of the ultrasonic pulses at the beginning of cracking. Thus, cracks of a few mm in length can be detected with a spatial resolution of about 2 cm.

Essential components of monitoring systems are sensors that can be applied or embedded. Piezoelectric sensor elements based on PZT or PVDF can detect the natural vibrations of components and provide information about cracks, delamination or changes in fastening. A few PZT ultrasonic transducers are sufficient to inspect large structures for emerging defects with spatial resolution using Lamb waves or acoustic emission. Rotor blades, aircraft components made of fiber composite materials, metal pipelines or large (composite) glass plates can be continuously monitored with minimal metrological effort.


Ultra-fast temperature changes can be detected without contact even at temperatures of over 1000° C using special ultrasonic transducers, thus avoiding critical process conditions. Depending on the application, the use of optical, thermal and/or chemical sensors can also be useful so that multi-sensor systems can be realized.