Development by numerical simulation
Numerical simulation begins with a hexahedral model, a finite element model that is subjected to specific loads and temperatures. A computer program then identifies which of the hexahedrons are critical for withstanding the stresses and which ones are not. The non-critical ones are removed one by one until only the essential structures remain. Next, the computer simulates dynamic stresses and their impact over thousands of takeoffs and landings. The model exposes any weak points where the hexahedral mesh needs to be modified.
In the next step, the design is optimized for additive manufacturing. Selective laser melting. In this process, thin layers of the high-temperature iron-nickel alloy Inconel 718 are applied to the substrate in powder form. A laser then melts the powder, fusing the layers together to create solid structures. In principle, this method is suitable for producing any geometry, but it does require any support structures and overhangs to be removed or reworked afterwards. Optimizing the model minimizes the amount of work involved.
The CAD data from the simulation can now be used for additive manufacturing without further processing. For quality assurance purposes, MTU’s engineers developed their own method for identifying any structural weak points as early as possible. During the welding process, a sensor records the time it takes for the powder melted by the laser to resolidify and cool down. If this is unusually long, it’s a sign that the powder has not fused properly with the layer below.
Production of the blank for the bracket takes only a few hours. Before the bracket is mounted, it undergoes further quality inspections to ensure it is safe to use in the engine.
The new bionic brackets are now being installed in a test engine. Once they have passed endurance testing and demonstrated they meet the requirements for approval, they can be rolled out into large-scale production. “Then we’ll have another important milestone under our belt, paving the way for more developments of this kind in the future,” Welling says. “Our plan is to produce 15 to 30 percent of our engine components using additive technologies by 2030. That’s no mean feat, and we know we’ve still got some challenges to overcome. But we’re working through them systematically to find solutions.”
There is a long list of components that would be suitable for additive manufacturing. Among the potential candidates are a housing with integrated cooling, lightweight engine blades or a redesigned variable guide vane actuator—a mechanism currently made up of many small parts that have to be assembled manually.
“Additive manufacturing can also help achieve the targets for reducing fuel consumption and emissions in aviation,” Welling says. “Following nature’s example, we can make aircraft engines lighter, quieter and more efficient.”