Smart steel to protect buildings from earthquakes and other risks

by Hans Diederichs

Smart materials such as shape memory alloys have so far mainly been used in the form of small components, for example in biomedical engineering in the form of stents that save the lives of many people. The use of the unique possibilities of these alloys is also attractive for many other industries. From aviation and the automotive industry to the construction sector, there are already many application ideas. However, the costs of the alloys currently available are usually too high to be used rationally in these industries. "Steels with shape memory effect are a promising alternative to existing alloys because they can be produced at low cost," says materials scientist Prof. Dr.-Ing. Thomas Niendorf from the University of Kassel. The new alloy and the underlying process were developed in one of his research projects funded by the German Research Foundation (DFG) and lead-managed by his colleague Malte Vollmer together with colleagues from the TU Bergakademie Freiberg and IFW Dresden. The results have now been published in the latest edition of the renowned research journal Nature Communications.

The researchers succeeded in qualifying one of these alloys for new applications in the construction industry by suitable chemical modifications. They used an iron alloy as the basis, which already showed smart properties, the so-called pseudo elastic behaviour, but only in the form of small laboratory samples. Using new alloy additives and an adapted process chain, they now adjust the alloy so skilfully that the previous limitations in component size have been overcome. The result is the world's largest single-crystalline structure realized in a smart steel, a breakthrough on the way to industrial application.

"Applications in the construction industry will benefit considerably from this. The smart steel will make it possible to protect bridges and structures in endangered regions from damage and destruction by earthquakes or high traffic loads," Prof. Niendorf is certain. "Their considerable pseudo elastic damping capacity, which significantly reduces the loads of corresponding critical events and thus protects the structures and can save human lives, is essential". Intensive discussions are already underway with colleagues in civil engineering in Kassel to use the new smart material in a targeted manner. With the SmartCon project under the leadership of Prof. Dr. Bernhard Middendorf (Department of Civil Engineering), a further research project has already been initiated. Niendorf sees enormous potential for the German economy in the new smart material: "From connecting elements for timber and solid construction to reinforcing elements for concrete buildings, its use is conceivable. The German steel industry relies on highly specialized steel grades, while the construction industry also relies on highly developed building materials such as ultra-high-strength concretes. A high level of interest on the part of these important sectors in Germany is obvious".

Shape memory alloys are based on a so-called martensitic transformation, which is completely reversible. After deformation, they return to their old shape when heated, which has given them their name. The search for new shape memory alloys is one of Prof. Dr.-Ing. Thomas Niendorf's main areas of research. He has held a professorship for metallic materials at the University of Kassel since 2015. In addition to shape memory alloys, he researches objects from the 3D printer. In both cases, the evaluation of the properties and reliability of the realized materials is an essential part of his team's research.

Source and photo: University of Kassel

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