Scientists from Peter the Great St. Petersburg Polytechnic University (SPbPU) are the first in Russia to design a friction stir welding technology relating to a new aluminum alloy for building a lightweight pedestrian bridge.
Image Credit: Peter the Great St. Petersburg Polytechnic University.
The engineers' objective is to implement a novel technique at the university. The researchers have planned to weld the elements and further connect them into a bridge at the construction site.
The aluminum pedestrian bridge is to be raised at the Bor town in the Nizhny Novgorod region of the Russian Federation. The planned bridge will be the 10th such project in Russia. However, the new alloy and friction stir welding technology will be employed in bridge construction for the first time.
The researchers had done this project in association with the SGR aluminum structures plant in St. Petersburg, and the project was supervised by the Aluminum Association of Russia.
The engineers will connect about 20 parts, measuring 8 m long and 16 mm thick made of aluminum. The work will be executed in the laboratory of Lightweight Materials and Structures of SPbPU. The researchers note that the new alloy had only recently become available for common use.
The bridge is large and has many types of connections.
Anton Naumov, Associate Professor, Institute of Mechanical Engineering, Materials and Transport, Peter the Great St. Petersburg Polytechnic University
Naumov also added that the scientific group is designing a friction stir welding technology for butt joints of aluminum plates on both sides of the plates. According to the researchers, these types of joints will be of a higher quality than arc welding.
The researchers also observed that it is also more profitable to weld thick aluminum sheets using this method. This is because arc welding involves using many more manipulations, for example, arc welding is done in many passes to fill the whole thickness of the seam with the filler wire. Furthermore, friction stir is a green technology due to the non-evaporation of materials or the absence of luminescence.
The new high-strength aluminum alloys successfully compete with the structural steels in terms of mechanical properties, also, in terms of weight, the aluminum structure will be much lighter than the steel ones. Therefore, the implementation of the aluminum bridges is increasing worldwide.
Anton Naumov, Associate Professor, Institute of Mechanical Engineering, Materials and Transport, Peter the Great St. Petersburg Polytechnic University
The welding technology is being designed by experts from the Laboratory of the Lightweight Materials and Structures SPbPU and will be subjected to quality control to ensure the safety of the structure.
Innovative technology of friction stir welding is already used in the bridge construction: the plant ‘Sespel’ uses it for the components of orthotropic plates from the well-known aluminum alloy 6082 T6. But the new bridge will be the first bridge in Russia manufactured using a friction stir welding technology for the new Al-Mg alloy.
Evgeny Vasiliev, Head, Transport Infrastructure, Aluminum Association of Russia
According to Vasiliev, the project is a critical task and an absolute technological advancement. The researchers are expecting to complete their part in the project by the end of September 2021. The bridge measuring 121 m in length is planned to be commissioned by 2022.