Non-destructive testing Using physics to look into bridges, pipelines and aircraft parts

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ETH Eidgenössische Technische Hochschule Zürich

GGB Heilbronn GmbH

A spin-off from ETH Zurich is using physics to examine the inside of bridges or aircraft components to check their stability. The technology was originally used to explore Mars.

When the unmanned NASA probe InSight landed on Mars at the end of 2018, it had a mission that had never been carried out before: to explore the inner structure of Mars. This was made possible by a highly sensitive seismometer co-developed by ETH Zurich. This records the finest vibrations caused by Marsquakes or meteorite impacts, for example.

However, it took more than just a measuring device to send the seismic data from the Mars probe to Earth and decipher it: the researchers at ETH Zurich therefore developed models and simulations with which they were able to deduce the structure of the Martian interior from the data. The technology can help not only on Mars.

The ETH spin-off Mondaic was created and Christian Boehm is now its managing director: "What enabled us to look inside Mars back then now helps us to look inside bridges, aircraft parts and other materials." To do this, we use waves from physics. For example, a wave is triggered by an ultrasound device and then moved through an object. The waves are reflected by an obstacle and change. This is where the sensors come into play. They measure how the pattern of the wave changes inside the object.

The technology behind it

The technical principle of Mondaic is easy to explain: a wave is triggered by an earthquake or an ultrasound device, for example, and moves through any object. This can be an entire planet, but also a concrete pillar or an airplane wing. Boehm and his team then use sensors to measure how the interior of the object changes the pattern of the wave through reflection.

The Mondaic engineers compare the data obtained with a digital twin of the object, which maps its physical properties. Boehm explains the process using a pipeline as an example: "For example, we use our software to simulate how an ultrasonic wave should move through the pipeline if it is not damaged. If the wave pattern of the real pipeline differs from that of its digital twin, Boehm and his team know that something is wrong. This allows them to calculate, among other things, that there must be cracks in the pipeline and where they are located.

Mondaic combines precise waves with efficient cloud technologies. This enables fast analysis in the cloud. "The efficiency of modern cloud applications makes our development suitable for everyday use and competitive," says Boehm. Thanks to the complete automation from data acquisition to the analysis result, our application can also be used by people who are not experts in physics.

Research software and a marketable product

Mondaic's software was originally developed as part of several research projects at the Chair of Seismology and Wave Physics. However, the path from code for research purposes to a marketable product was fraught with numerous obstacles: "We had to rethink everything to make the software stable and user-friendly and to fully automate the application. This started with the measurement data and ended with the finished image," says Boehm.

The strength of Mondaics lies in the combination of precise physics and efficient cloud technology. What was previously only possible on high-performance computers can now be calculated in the cloud in just a few minutes. "The efficiency of modern cloud applications also makes our technology suitable for everyday use and competitive outside of research," explains Boehm.

Investigating dilapidated bridges

In Germany, the Mondaic team is investigating the condition of bridges together with the Federal Institute for Materials Research and Testing and the company Vallen Systeme. The main focus here is on acoustic emission data. "This method is also known as micro-seismology, because the crack in a prestressed prestressing cable inside a bridge acts like a small earthquake and we can determine this with our software," says Boehm.

Compared to the ConScope technology, which is based on findings from earthquake research and uses coda waves to detect cracks, Mondaic relies on a direct comparative analysis of the real data with digital twins of the structures to be tested. Both methods aim to detect structural weaknesses at an early stage and thus sustainably increase the safety of buildings.

Testing carbon fiber reinforced plastic

The technology also has potential in the aerospace industry. Together with the University of Applied Sciences Northwestern Switzerland and researchers from ETH Zurich, Boehm and his team tested a component made of carbon fiber-reinforced plastic, such as that used in the outer shell of aircraft. Mondaic's software was able to detect damage that occurred during production. "This shows the potential of our process for the quality control of high-tech components," says Boehm.

What began as a scientific tool for exploring Mars is now helping to make components and infrastructure on Earth safer. But Boehm is not quite finished with the red planet yet: "Perhaps one day a component tested by Mondaic will fly to Mars. But until then, we have enough to do here on Earth." (heh)