The researchers at Fraunhofer IKTS are focused on a clear approach: replacing universal, expensive measurement technology with systems optimized for specific applications. “Most applications only need a small fraction of these expensive all-in-one solutions. Instead of taking a one-size-fits-all approach, we therefore develop our monitoring technology precisely for specific structures such as bridges, pressure vessels, chemical plants or wind turbines. This enables us to significantly reduce costs,” explains Lars Schubert, Head of the Condition Monitoring and Test Services Department at Fraunhofer IKTS. “We expect even greater cost savings in the future from economies of scale.”

Acoustic emissions: when structures “speak”

The technology is based on a physical principle: Damage such as cracks or breaking steel tendons emits acoustic signals as it occurs. Sensors detect, localize and analyze these acoustic emissions. “It's like a taut guitar string snapping. Every time damage occurs, it produces a characteristic sound that we can detect and pinpoint spatially with our technology,” explains Fraunhofer IKTS research scientist Kilian Tschöke. In contrast to traditional testing methods that are only used at intervals, COMOBASE enables continuous monitoring—like a permanent stethoscope for structures. This monitoring focuses especially on low-frequency ranges that can better penetrate solid structures. This is achieved by affixing acoustic sensors to strategic points on the structure. Future applications might also use MEMS (micro-electromechanical systems) sensors.

The researchers have developed application-specific electronics for the measurement technology acquiring the signals. The system is based on PCUS technology developed at Fraunhofer IKTS and connects to the sensors with modular measurement and interface cards. A basic system processes 32 channels in parallel. A provided software development kit enables system interaction using the customer's own test software. “Our offer is highly customized. We deliberately omit technical features that are not required for monitoring. This lets us make the hardware and software significantly leaner and more cost-effective,” says Fraunhofer IKTS research scientist Lars Schubert.

The new solution mainly targets consulting engineering firms contracted to prepare reports for local governments and infrastructure operators. “We offer engineering consulting firms a comprehensive and individualized package for identifying and assessing infrastructure damage and evaluating the associated structural risk,” says Tschöke. 

Successful validation in real-world use

COMOBASE is already in use in current field tests in parallel with established systems on a real bridge structure. The results speak for themselves: “Our validations confirm that we can achieve the same conclusive results with significantly reduced system complexity,” says Schubert.

In the next step, Fraunhofer IKTS plans to further develop other technologies such as fiber-optic sensors for infrastructure monitoring. The Fit4Infrastructure project is also establishing a center for testing and monitoring methods for infrastructure applications at the Fraunhofer IKTS location in Dresden-Klotzsche.