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Aerospace

New Lattice Structure Absorbs Dreadful Vibrations from Propellers, Rotors and Rockets

01 August 2016

If you’ve ever ridden a bus, you know that the bus engine can sometimes emit vibrations that can be felt through the seats. Similarly, vibrations from the propellers or rotors in propeller aircraft and helicopters can make flights bumpy and loud, as well as weakening the aircraft and its components.

Engineers have now come up with a solution to the vibrations in machines, vehicles and aircraft with a new three-dimensional lattice structure that can expand the possibilities of vibration absorption.

The vibration absorbing lattice in a vision of the future. It could be used one day in rockets. (Image Credit: 3Dsculptor / Shutterstock /Jung-Chew Tse) The vibration absorbing lattice in a vision of the future. It could be used one day in rockets. (Image Credit: 3Dsculptor / Shutterstock /Jung-Chew Tse)

The lattice structure can absorb a wide range of vibrations while acting as a load-bearing component, for objects like propellers, rotors and rockets. The structure can absorb vibrations in the audible range, which are the most undesirable in engineering applications.

The ETH Zurich team, led by Chiara Daraio, Professor of Mechanics and Materials, is responsible for developing this new technology. The structure has a lattice spacing of around 3.5 mm and is made out of plastic using a 3-D printer. Steel cubes smaller than dice are embedded within the lattice and act as resonators.

"Instead of the vibrations traveling through the whole structure, they are trapped by the steel cubes and the inner plastic grid rods, so the other end of the structure does not move," says Kathryn Matlack, a post-doctoral student in Daraio's group.

Materials that absorb vibrations already exist in certain machines and household appliances— using mostly soft materials to partially absorb the vibrations-- the new vibration-absorbing structure is rigid and can therefore also be used as a load-bearing component, for instance in mechanical engineering or even in airplane rotors and helicopter propellers.

The new structure offers another major advantage. Compared to existing, soft absorption materials, it can absorb a much wider range of vibrations, and is particularly good at absorbing relatively slow vibrations.

"The structure can be designed to absorb vibrations with oscillations of a few hundred to a few tens of thousand times per second (Hertz)," says Daraio. "This includes vibrations in the audible range. In engineering practice, these are the most undesirable, as they cause environmental noise pollution and reduce the energy efficiency of machines and vehicles."

According to the researchers, technically it would be possible to build such a construction out of aluminum and other lightweight metals instead of plastic. This would require a combination of lightweight material structured in a lattice geometry, and embedded resonators with a larger mass density. The geometry of the lattice structure and the resonators would need to be aligned to the anticipated vibrations.

While the vibration absorbers are ready for technical applications, they are limited in terms of 3D printing technology, which is mostly geared toward small-scale production and material properties. Therefore, load-bearing capacity cannot yet match those of components manufactured with traditional methods. Once the technology is ready for industrial use, there are much broader applications for it. For example, it could be used in wind turbine rotors, where minimizing vibrations would increase efficiency, as well as in vehicle, aircraft and rocket construction.

To contact the author of this article, email Nicolette.Emmino@ieeeglobalspec.com


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