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Computational Models for Non-linear Mechanical Loading Analyses of Lattice Structures Made by Laser Powder Bed Fusion
Červinek, Ondřej ; Dr. Michael R. Tucker (oponent) ; Haas/, Franz (oponent) ; Koutný, Daniel (vedoucí práce)
The development of additive technologies in recent years has enabled the manufacturing of metamaterials with porous internal architecture, called lattice structures, from several types of metal alloys. With these structures, it is possible to develop lightweight parts with potential in the field of mechanical energy absorption. Their implementation in vehicle deformation zones can increase the safety of passengers. The properties of structures allow to design absorbers with specific type of behavior which reduce the overload applied on the vehicle crew during an accident. To use these parts for specific applications, it is necessary to estimate their deformational behavior. Recent research has shown that the parent material of these structures has properties different from those of conventional bulk components produced by the same technologies. It means that, for efficient use of lattice structures, their specific properties and deformation characteristics must be accurately mathematically described. However, a mathematical model that would consider a description of all significant deformation characteristics of lattice structures is not available. Therefore, this thesis focuses on development of non-linear numerical model of lattice structures loading with inclusion of the most significant geometrical imperfections, specific properties of multi-strut samples and dynamic effects. The structures are made of aluminum alloy AlSi10Mg and stainless steel 316L using the selective laser melting technology. Two different finite element analysis approaches are used to create the geometry model that allows inspection of the deformation features in detail. The results of both models confirm that geometrical imperfections related to a change in shape and cross-sectional area of the strut have a significant impact on the resulting mechanical properties. Their inclusion in the geometry model improves the accuracy of the simulation results. Furthermore, the mechanical properties of lattice structures determined by multi-strut samples significantly better represent properties of structures for quasi-static and dynamic loading. The final parameter verification simulation of lattice structures loading at several velocities shows good agreement between the experiment and the computational solution. A similar parametrical study can lead to the finding of efficient structure configurations determined for a specific amount of absorbed energy without prior manufacturing and testing.
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