Metal 3D Printing Extends the Service Life of Steel Components
Empa researchers are investigating how steel structures, such as bridges, can be specifically repaired or even redesigned in the future—using metal 3D printing.
Steel bridges, structural systems, and industrial structures are often subjected to loads for decades. As they age, fatigue cracks can compromise safety. However, replacing permanently installed components is often impractical or very costly. Researchers at Empa are therefore investigating how steel components can be selectively repaired using metal 3D printing. They are employing the “Wire Arc Additive Manufacturing” (WAAM) process, in which a welding wire is applied layer by layer to defective areas using an electric arc.
Metal 3D Printing with Custom Geometry
Unlike conventional welding, metal 3D printing not only joins components together but also enables reinforcements with custom-designed geometries. This allows damaged areas to be reinforced locally without having to replace the entire component. “The key is not to apply as much material as possible,” explains Hossein Heydarinouri from Empa’s Engineering Structures Department. “The shape is much more important: An optimized geometry distributes stresses in such a way that the propagation of existing cracks is stopped or significantly slowed down.” As part of a joint master’s thesis project between Empa and ETH Zurich, this approach extended the service life of damaged steel plates by up to four times.
Great Potential for Metallic 3D Printing
In extensive testing, cracked steel plates were fitted with differently shaped metal reinforcements and then subjected to repeated loading. All reinforced specimens exhibited a significantly higher fatigue life than unrepaired control plates. Two-layer, stepped reinforcement geometries proved particularly effective. At the same time, the study showed that an unfavorable geometry can cause new stress concentrations. “Our results demonstrate how important it is to design the reinforcement structure specifically for this purpose,” said Heydarinouri. In the long term, Empa sees further potential for WAAM. In addition to repairing damaged components, the combination of intelligent geometries, metallic 3D printing, and new materials could lead to the development of lightweight, high-strength, and adaptive metal structures for the steel and mechanical engineering industries in the future.
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