What is it all about? In nature, especially in aquatic plankton organisms (diatoms, radiolarians), complex, irregular lattice structures are found. What influence do bio-inspired lattice structures have on vibrational properties?

What did we find out? Irregular lattice structures can increase the natural frequencies compared to regular lattice structures. The figure shows an example of a regular (left) and an irregular (right) lattice.

Details about the work can be found in this publication: Andresen et al. (2020): Eigenfrequency maximisation by using irregular lattice structures, Journal of Sound and Vibration 465.

This sub-project was conducted in cooperation with the Deutschen Zentrum für Luft- und Raumfahrt (DLR).

What is it all about? Complex honeycomb structures can be found in many diatom shells. Do these influence the vibrational behavior of honeycomb plates?

What did we find out? Irregular honeycomb structures have higher natural frequencies than regular honeycomb panels. The figure shows how the natural frequency increases from a solid plate via regular honeycomb plates to an irregular honeycomb plate.

Details about the work can be found in this publication: Andresen S. (2021): Impact of Bio-inspired Structural Irregularities on Plate Eigenfrequencies, In: Sapountzakis E.J., Banerjee M., Biswas P., Inan E. (Hrsg.): Proceedings of the 14th International Conference on Vibration Problems. Lecture Notes in Mechanical Engineering, Springer, Singapore.

What is it all about? Can the vibrational properties of magnet carrier structures in particle accelerators be improved by using bio-inspired structures and optimization methods? Which boundary conditions and components of magnet carrier structures influence the vibrational properties of the entire structure? The studies focus on the PETRA IV synchrotron radiation source, which is currently being developed at the Deutsches Elektronen-Synchrotron (DESY) in the PETRA IV project.

What did we find out? A first study showed that the use of bio-inspired structures in support structures increases natural frequencies and stiffness and reduces mass. Details of the study can be found in the following publication 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.

In a large parameter study, the influence of various boundary conditions and components of a magnetic carrier structure on the vibration properties was investigated. This study was of great importance for the subsequent development of a bio-inspired carrier structure. Details of the study can be found in the publication S. Andresen (2021) Impact of Different Components and Boundary Conditions on the Eigenfrequencies of a Magnet-Girder Assembly. Instruments 5(3), 29.

An optimized support structure for PETRA IV was developed with the help of biologically inspired structures and optimization processes. The 3m-long structure features irregular honeycomb structures, sandwich elements, soft transitions and hierarchical structural branches, among other things, as can be seen in the picture below. Production was carried out in a casting process using 3D-printed sand cores. Natural frequency measurements on the manufactured structure (see image below) validated the numerical models.
More information about the development process, the production and the subsequent vibration experiments can be found here:

S. Andresen, N. Meyners, D. Thoden, M. Körfer, C. Hamm (2023) Biologically Inspired Girder Structure for the Synchrotron Radiation Facility PETRA IV. Journal of Bionic Engineering 20, 1996-2017

Vorbild Strahlentierchen. Wie eine ungewöhnliche Allianz zwischen Physikern und Meeresbiologen schwere Magnete auf neuartige Beine stellt, DESY Forschungsmagazin femto, 01|2022, pp. 38-41

What is it all about? The influence of structural irregularities in lattice structures on the natural frequencies has already been investigated. This project is about the damping properties. The shells of the diatoms are not only cracked open by the predators, but also shaken. It is to be expected that the shell dampens these vibrations in order to protect the algae. So can the damping properties be improved by using bio-inspired, irregular lattice structures?

What did we find out? By using specific irregular properties, the damping in the lattice was significantly improved compared to the regular lattice across different frequencies. The figure shows an example of an investigated regular (right) and irregular (left) grating of the same mass. The irregular grating showed a more complex and frequency-sensitive behavior, while the regular grating showed a smoother, monotonic decrease of the loss factor and damping coefficient with increasing frequency. As in sub-project 1, the irregular grids were also significantly stiffer and had higher natural frequencies.

What are we currently working on? We are currently working on the final evaluation of the measurement results from the damping tests and will then publish the study.

What is it all about? Diatom shells exhibit deformations that correspond to vibrational modes (Gutiérrez et al. 2017). What happens to the natural frequencies when structures are deformed according to their eigenmodes?

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

What did we find out? If a beam (1D) or a plate (2D) is deformed according to its eigenmodes, the natural frequencies increase very sharply. The figure shows an example of a beam and a plate that are deformed according to their first mode of vibration, as a result of which the associated frequency has increased enormously.

Details of the study can be found in the following publication: 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 12(11). pp.1-18.

What are we currently working on? We are currently investigating whether this efficient method for maximizing natural frequencies can also be applied to a wide variety of 3D structures.

What is it all about? As already mentioned, diatoms are not only cracked open by their predators, but also shaken. Until now, it has not been possible to measure the natural frequency of these very small organisms. Nevertheless, it is of great importance to know the vibrational properties of the complex shells. What influence do certain structural parameters have on the natural frequencies of the entire structure?
In this study, shell structures with different structural elements of diatoms are to be constructed and the natural frequencies calculated numerically.

What did we find out? Various shells of different complexity, as shown in the figure below, were constructed and the natural frequencies were calculated numerically. The results show that certain structural parameters significantly shift the natural frequencies, while other structural elements hardly influence the natural frequencies.

The results are presented in a publication:

Andresen, S.; Linnemann, S.K.; Ahmad Basri, A.B.; Savysko, O.; Hamm, C. Natural Frequencies of Diatom Shells: Alteration of Eigenfrequencies Using Structural Patterns Inspired by Diatoms. Biomimetics 2024, 9, 85. https://doi.org/10.3390/biomimetics9020085

What is it all about? The targeted shifting of natural frequencies and the improvement of damping properties are of great interest for many technical applications. Can the knowledge gained in the sub-projects be transferred into software modules that are available to engineers for application to a wide variety of components?

What have we found out? The initial results of the previous sub-projects have already been converted into algorithms and integrated into the powerful product development software Synera. The algorithms are available to users of the software as modules that they can apply to their components. This allows natural frequencies to be shifted quickly and automatically, damping properties to be improved, stiffness to be increased and weight to be reduced. For example, the components shown in the illustration allow components (2D and 3D) to be deformed according to natural modes in order to maximize the natural frequencies.

What are we currently working on? We would like to transfer all findings into the software in order to make them available to users from a wide range of industrial sectors. In this way, lightweight structural problems in NVH (noise, vibration, harshness) can be tackled efficiently and without a great deal of preliminary work using bio-inspired structures and optimization methods.
Consequently, we are currently developing additional components that allow users of the software to generate lightweight high-frequency structures. This involves reducing the volume based on the eigenvector distribution of the structure and replacing it with various bio-inspired structural elements.