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Veränderung der lokalen topologischen und geometrischen Eigenschaften von Titan 3D-Netzwerkstrukturen unter Kompression
Citation Link: https://doi.org/10.15480/882.9632
Publikationstyp
Doctoral Thesis
Date Issued
2024
Sprache
German
Author(s)
Advisor
Referee
Krill, Karl
Title Granting Institution
Technische Universität Hamburg
Place of Title Granting Institution
Hamburg
Examination Date
2024-03-15
Institute
TORE-DOI
Citation
Technische Universität Hamburg (2024)
The Gibson-Ashby relation is often used to establish a correlation between the mechanical properties of metallic foams and their porosity or density. However, this relation is applicable strictly to low-density foams. To enhance the ability of structural models to describe the experimental mechanical behavior, various modifications have been introduced in the literature, such as considering an effective density by subtracting non-load-bearing parts, accounting for variations in node distances within the network, and incorporating the number of linarly independent closed loops per volume as a measure of global network connectivity.
In many cases, the mechanical behavior of porous metals cannot be predicted solely based on the parameters mentioned above. The objective of this study is to identify additional local topological features that have an impact on the mechanical properties.\\
Bicontinous titanium, as a model material, and two-phase composites made of titanium and magnesium with identical structures were fabricated using liquid metal dealloying. Compression tests were conducted in an x-ray nanotomograph to investigate the deformation. The reconstructed structures were simplified through skeletonization and the resulting skeleton was represented as a weighted graph. This enabled the calculation of a ring basis for the network, to do statistical analysis of the closed loops as the structure building elements. This new method allows the discription of topological changes of the structure and geometrical changes of the structure building elements. A key finding was that the deformation in both cases primarily occurred through the deformation of larger structural units, while smaller rings changed position, but not their shape within the network. The formation of contacts between ligaments in the porous samples and the additional lateral expansion of the rings in the two-phase composites were observed. This study introduces a novel perspective on deformation of porous metals through a model based on the size distribution of structural building units.
In many cases, the mechanical behavior of porous metals cannot be predicted solely based on the parameters mentioned above. The objective of this study is to identify additional local topological features that have an impact on the mechanical properties.\\
Bicontinous titanium, as a model material, and two-phase composites made of titanium and magnesium with identical structures were fabricated using liquid metal dealloying. Compression tests were conducted in an x-ray nanotomograph to investigate the deformation. The reconstructed structures were simplified through skeletonization and the resulting skeleton was represented as a weighted graph. This enabled the calculation of a ring basis for the network, to do statistical analysis of the closed loops as the structure building elements. This new method allows the discription of topological changes of the structure and geometrical changes of the structure building elements. A key finding was that the deformation in both cases primarily occurred through the deformation of larger structural units, while smaller rings changed position, but not their shape within the network. The formation of contacts between ligaments in the porous samples and the additional lateral expansion of the rings in the two-phase composites were observed. This study introduces a novel perspective on deformation of porous metals through a model based on the size distribution of structural building units.
Subjects
Tomographie
Netzwerkstrukturen
Titan
Magnesium
mechanische Eigenschaften
DDC Class
620.1: Engineering Mechanics and Materials Science
660: Chemistry; Chemical Engineering
530: Physics
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Stefan_Berger_Dissertation-Veränderung der lokalen topologischen und geometrischen Eigenschaften von Titan 3D-Netzwerkstrukturen unter Kompression.pdf
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