Safer road barriers with high strength steels
By switching to high strength steels in road barriers, safety can be even better, while a smaller amount of steel needs to be used in the thinner beams. The results are presented in a three-year EU project that was recently completed, where Luleå University of Technology had an important role in material testing.
– Real tests show that road barriers with high strength steel can capture a load of 44 tons at 70 km/h, compared to today's highest standard, which is 38 tons at 70 km/h. In addition to cope with larger loads from crashes, high-strength steel means thinner barriers, which saves material and the environment, says Esa Vuorinen, Associate professor in Materials Engineering at Luleå University of Technology.
Three times stronger
The EU project HIPEBA has been going on for three years with the aim of introducing high strength steel in road barriers. The biggest challenge has been to achieve a good combination of strength and toughness. Another challenge has been to protect the steel from corrosion, which is done by dipping the steel in molten zinc at 460 degrees for about four minutes.
– We were able to solve both these challenges. A high strength steel, manufactured by SSAB, between 500-700 MPa (a standard measure of strength) proved to work very well, equivalent to a strength that is about two to three times higher than the galvanized steel used today. It was also possible to galvanize the high strength steel without deteriorating the strength, says Esa Vuorinen.
The material researchers at Luleå University of Technology contributed with mechanical testing, where the strength of the steel at normal and accelerated speed has been tested. They have also examined the toughness of the material as well as the microstructure. In addition to testing the high strength steels, they have also examined that the welded joints hold up.
– We have good skills in mechanical testing and microstructure research. We are also innovative in terms of material development, where we have contributed historically, and we will continue to do that in the future, says Esa Vuorinen, who is also asked if and when we will see the new barriers on our roads?
– My guess is that we will see road barriers with high strength steel within 10 years. Road safety is important, but it is also necessary for manufacturers to take on the new knowledge, breaking some traditional thinking.
The HIPEBA (High Performace Steel for Safer and More Competitive Barriers) project is funded by the Research Fund for Carbon and Steel (RFCS). Participants in the project were, in addition to Luleå University of Technology, SSAB (Sweden), CSM (Italy), Cidaut (Spain), Copro (EU), Hiasa (Spain) and STA (UK).
See the film below where the project is described, and also contains images from the crash test.