Smart screws allow remote monitoring of critical structures

Technology that allows the stability of the screw connections of critical infrastructure, as well as machines and production facilities to be checked at any time by remote monitoring, has been developed by researchers in Germany.

Wear and impact from phenomena such as temperature fluctuations or vibrations can cause the screws to loosen or even become completely detached. This can be fatal and, as a result, regular inspections of safety-critical structures are required.

The new solution, known as “Smart Screw Connection”, combines sensors with radio technology and promises to reduce the time and effort spent on these inspections, while improving safety.

Developed by a team of researchers from the German applied research organization Fraunhofer’s Cluster of Excellence Cognitive Internet Technologies (CCIT), Smart Screw Connection comes with a screw equipped with a washer equipped with a piezoresistive thin film “DiaForce”.

When the screw is tightened, the pressure-sensitive sensors register the preload force at three points. Any change in the preload force changes the electrical resistance in the film.

“When a screw loosens, the resulting change in resistance is reported to a radio module located on the head of the screw,” explained project manager Dr. Peter Spice. “The radio module, in turn, sends the data to a base station, which collects information from all relevant screws in the site.

The technology is able to send small packets of data over long distances, consuming minimal energy from more than 100,000 sensors through a single base station. The software program then displays the data for each individual screw in a graphical overview. Depending on the configuration and application, the status of the screw connections can be transmitted continuously, based on an event or at certain intervals.

“This remote monitoring system allows us, for the first time, to monitor the stability of safety-critical infrastructures at all times, even remotely, and to properly inspect each respective screw,” added Dr. Spice.

“It’s a major asset in terms of security. An inspection of a bridge or wind turbine does not require an engineer to be on site and inspect each screw individually, as all data is transmitted by radio to the service center. ”

The intelligent screw connection can be adapted to a wide variety of applications. In addition, the system operates on the principle of energy collection, which involves the use of heat or light to generate electricity and makes the system self-powered.

During installation, each individual screw together with the sensor module and the radio module is placed in a shielded programming box. The box gives the screw an individual encryption key, and the radio connection to the base station is also encrypted during data transmission. “In this way, we prevent criminals or hackers from sabotaging the system,” Dr. Spice explained.

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