Impact of biologically inspired structures on the vibration characteristics


Background and motivation
Each structure shows a characteristic natural vibration defined by a frequency (natural frequency, eigenfrequency) and an oscillation shape (mode shape, eigenmode). If the frequencies of external vibrations acting on a structure match the eigenfrequencies, the vibration amplitude can increase strongly. It is important to avoid these resonance phenomena, because they can lead to structural destruction. One way to prevent resonance is to shift the eigenfrequencies in such a way that they do not coincide with external frequencies anymore. And that is exactly what this project is about: increasing (maximizing) structural eigenfrequencies using biologically inspired structures and optimization processes.
In cooperation with the German Electron Synchrotron (DESY) in Hamburg, the research findings will be applied to a magnet carrier structure (girder) for the new PETRA IV particle accelerator in order to achieve high eigenfrequencies and a high rigidity as well as a low mass.
Investigating the influence of structural components on the natural vibrations of structures is of great interest for many areas of application. Possible fields of application include mechanical engineering, aerospace, automotive, construction, and optics.


Objectives and approach
The project includes several small projects that are carried out:

  1. Influence of biologically inspired, complex lattice structures on the eigenfrequencies
  2. Influence of biologically inspired, complex honeycomb structures on the eigenfrequencies
  3. Influence of structural deformations according to the mode shapes, as can be found in diatoms, on the eigenfrequencies
  4. Generating a development process for an optimized, biologically inspired magnet carrier structure (girder) for the currently planned particle accelerator PETRA IV (DESY)
  5. Influence of biologically inspired, complex structures on the damping properties
  6. Formulation of general principles to maximize structural eigenfrequencies (algorithms) that are integrated into an optimization software

Some of these sub-projects have been completed and the results have been published. Please take a look at the information about each sub-project below


Latest News
Talk at the “International Conference on Vibration Problems“ 2021 in Zurich, Switzerland (January 14th-15th, 2021)
"Shape Adaptation of 1D, 2D, and 3D Structures to Increase the Eigenfrequencies" (S. Andresen, S. K. Linnemann, L. M. Lottes, O. Savysko, R. Kienzler)


Final theses
Within the framework of this project final theses can be carried out. Unsolicited applications are welcome and can be sent to Sandra Coordes. It is important to us that the application contains your own motivation, educational background and previous practical experience.


Publications
S. Andresen, (2021): Impact of Bio-inspired Structural Irregularities on Plate Eigenfrequencies. In: Sapountzakis E.J., Banerjee M., Biswas P., Inan E. (eds) Proceedings of the 14th International Conference on Vibration Problems. Lecture Notes in Mechanical Engineering. Springer, Singapore.

S. Andresen, L. M. Lottes, S. K. Linnemann, R. Kienzler (2020): Shape adaptation of beams (1D) and plates (2D) to maximise eigenfrequencies. Advances in Mechanical Engineering Volume 12(11). pp 1-18

S. Andresen, A. Bäger, C. Hamm, (2020): "Eigenfrequency maximisation by using irregular lattice structures". Journal of Sound and Vibration

Andresen, S. (2019): “Improving vibration characteristics by using bio-inspired structures“, In: Kesel, A.B., Zehren, D. (Eds): Bionik: Patente aus der Natur. Innovationspotenziale für Technologieanwendungen, 9. Bremer Bionik-Kongress

Andresen S. (2018): “Optimizing the PETRA IV Girder by Using Bio-Inspired Structures”, In: Schaa V.R.W., Tavakoli K., Tilmont M. (Eds): Proceedings of the 10th Mechanical Engineering Design of Synchrotron radiation equipment and Instrumentation (MEDSI’18) Conference, JACoW Publishing, Geneva, Switzerland, pp. 297-301.

Andresen, S. (2018): „Untersuchung von Eigenschwingung und Leichtbaupotenzial unterschiedlicher Gitterstrukturen am Beispiel von Magnetuntergestellen von Teilchenbeschleunigern“, NAFEMS Online-Magazin 4, 57-63

Project execution:
Simone Andresen (project manager)
Oleksander Savysko

Contact: 
Simone Andresen
+49 (0)471 4831 2827
Mail

Duration:
December 2018 until December 2020
December 2020 unti June 2023
(3 years + 2.5 years extension)

Funding:
AWI Innovations Fond, DESY

Final thesis:
Final theses can be written in this project



Sub-project 1 (completed):

In nature, especially in aquatic plankton organisms (diatoms, radiolarians), complex, irregular grid structures can be found. How do these complex lattice structures influence the vibration properties?
 

Irregular lattice structures lead to a significant eigenfrequency increase compared to regular lattice structures. The figure shows exemplarily a regular (left) and an irregular (right) lattice structure.

For more details about this study it is referred to the following paper:
Andresen et al. (2020): “Eigenfrequency maximisation by using irregular lattice structures”, Journal of Sound and Vibration 465.

This sub-project was carried out in collaboration with the German Aerospace Center (DLR).
 



Sub-project 2 (completed):

Complex honeycomb structures can be found in many diatom shells. Do these irregularities influence the vibration behavior of honeycomb plates?
 

Irregular honeycomb structures show higher eigenfrequencies than regular honeycomb plates. The figure shows how the first eigenfrequency increases from a solid plate via regular honeycomb plates to an irregular honeycomb plate.

For more details about this study it is referred to the following paper:
Andresen S. (2021): “Impact of Bio-inspired Structural Irregularities on Plate Eigenfrequencies”, In: Sapountzakis E.J., Banerjee M., Biswas P., Inan E. (Eds): Proceedings of the 14th International Conference on Vibration Problems. Lecture Notes in Mechanical Engineering, Springer, Singapore.
 



Sub-project 3 (ongoing):

Diatom shells show deformations that correspond to mode shapes (Gutiérrez et al. 2017). What happens generally, when structures are deformed according to their mode shapes?

(Gutiérrez et al. 2017: “Deformation modes and structural response of diatom frustules“, Journal of Materials Science and Engineering with Advanced Technology 15)
 

If a beam (1D) or a plate (2D) are deformed according to their mode shapes, the eigenfrequencies increase enormously! The figure shows an example of a beam and a plate that are deformed according to their first mode shape, which leads to a strong increase of the corresponding frequency.

For more details about this study it is referred to the following paper:
Andresen et al. (2020): “Shape adaptation of beams (1D) and plates (2D) to maximise eigenfrequencies”, Advances in Mechanical Engineering 12(11).

We are currently investigating whether this efficient method for eigenfrequency maximization can also be applied to 3D structures.
 



Sub-project 4 (ongoing):

Can we use bio-inspired, complex structures to improve the properties of magnet carrier structures (girders) in particle accelerators?

A first study showed that the use of biologically inspired structures in girders increases the eigenfrequencies and the stiffness at a simultaneous mass reduction.

For more details about this study it is referred to the following paper:
Andresen S. (2018): “Optimizing the PETRA IV Girder by Using Bio-Inspired Structures”, In: Schaa V.R.W., Tavakoli K., Tilmont M. (Eds): Proceedings of the 10th Mechanical Engineering Design of Synchrotron radiation equipment and Instrumentation (MEDSI’18) Conference, JACoW Publishing, Geneva, Switzerland, pp. 297-301.
 

By using biologically inspired structures and optimization processes, an optimized girder structure for PETRA IV has been developed and manufactured in a complex casting process. The following picture shows a detail from the cast component, on which a complex honeycomb structure can be seen.

Vibration measurements on the cast component will soon be carried out at DESY to validate the simulation results. In addition, the cast support structure is used to investigate the application of other components (magnets, motorized sub-structures).

Afterwards, the development process that has been set up for the girder design will be complemented with new boundary conditions and carried out again.
 



Sub-project 5 (open):

The shells of the diatoms are not only cracked by the predators (copepods), but also shaken. It is expected that the shell structure damps these vibrations to protect the inner algae. This is what we want to investigate!

It will be studied how complex, irregular structures influence the damping properties.
 



Sub-project 6 (open):

The directed shift of eigenfrequencies is of great interest for many areas of application. Can we transfer the knowledge gained in the previous sub-projects to other structures/components?

The results of the previous sub-projects will be transferred into algorithms and integrated into an optimization software in order to be available for future structural optimization problems of different application areas.
 


Funded by the AWI Innovation Fund and DESY.