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Habilitationsschriften:

T. Daxner:
"Instabilities Limiting the Capacity of Lightweight Materials and Structures";
Fakultät für Maschinenwesen und Betriebswissenschaften, TU Wien, 2008.



Kurzfassung englisch:
Lightweight materials and structures derive their advantageous weight specific properties from arranging thin and/or slender structural elements in a structurally favorable way. By reducing the thickness in shell-like structures in combination with the introduction of stiffeners, and by replacing solid components by finely-resolved space-filling structures, the weight-specific properties will, in general, be improved. Representatives of the latter design principle are cellular materials which have found their way into many technical applications in the form of polymer and metallic foams. Placing material in regions, where it makes a maximum contribution to the stiffness and the strength of the component is another aspect of lightweight design, which is realized by the sandwich design pattern. For the design of stiff and strong shell-like components the introduction of a favorable curvature allows for further reducing the shell thickness.

While all the described structured materials and structures are geared towards improving weight-specific properties, their strength in absolute terms is quite often limited by the occurrence of instabilities, which are the principal topic of the present thesis. These instabilities, which comprise elastic buckling, elasto-plastic buckling, as well as material instabilities in the form of necking, are treated on several length-scales ranging from individual struts and cell walls in cellular materials (micro-scale), via structured sandwich core materials (meso-scale) to whole shells (macro-scale).

On the micro-scale, a review of modeling and simulation approaches for the prediction of the failure mechanisms and the strength (and stiffness) of 2D and 3D cellular structures is given along with the description of some state-of-the art unit-cell models for cellular materials with various micro-geometrical topologies. A sizing optimization problem for corrugated board in the presence of constraints on the local and global buckling strength is presented as an example of instabilities on a mesomechanical level. Lastly, the elasto-plastic buckling of a cylindrical shell during a conical expansion process is presented as an example for an instability on the macro-scale along with an examination of the necking process that is associated with material instability and represents one of the possible forming limits of this process.

Within this scope, the present thesis gives an overview over modeling and simulation approaches involving structural and material instabilities and their application to structures relevant for lightweight design.

Erstellt aus der Publikationsdatenbank der Technischen Universität Wien.