Abstract
Selective laser melting (SLM) is an additive technology that allows for the production of precisely designed complex structures for energy absorbing applications from a wide range of metallic materials. Geometrical imperfections of the SLM fabricated lattice structures, which form one of the many thin struts, can lead to a great difference in prediction of their behavior. This article deals with the prediction of lattice structure mechanical properties under dynamic loading using finite element method (FEA) with inclusion of geometrical imperfections of the SLM process. Such properties are necessary to know especially for the application of SLM fabricated lattice structures in automotive or aerospace industries. Four types of specimens from AlSi10Mg alloy powder material were manufactured using SLM for quasi-static mechanical testing and determination of lattice structure mechanical properties for the FEA material model, for optical measurement of geometrical accuracy, and for low-velocity impact testing using the impact tester with a flat indenter. Geometries of struts with elliptical and circular cross-sections were identified and tested using FEA. The results showed that, in the case of elliptical cross-section, a significantly better match was found (2% error in the Fmax) with the low-velocity impact experiments during the whole deformation process compared to the circular cross-section. The FEA numerical model will be used for future testing of geometry changes and its effect on mechanical properties.
Highlights
Energy absorbers made of porous materials are currently used to absorb mechanical energy caused by impact or high velocity deformation due to their high efficiency of energy absorption and low weight [1,2,3]
The results showed that the simplified core is only suitable for prediction of the first progressive collapse of the lattice structure, while the beam geometry allows for the prediction of the whole deformation process due to the preserving topology of the core
The results show that the Selective laser melting (SLM) technology allows to produce energy absorbers from AlSi10Mg alloy, which can effectively absorb energy through self-deformation
Summary
Energy absorbers made of porous materials are currently used to absorb mechanical energy caused by impact or high velocity deformation due to their high efficiency of energy absorption and low weight [1,2,3]. There are several types of commercially produced porous materials, e.g., hexagonal honeycomb structures [4], metal foams [5,6,7], or laminated composite fiber blocks [8]. They usually have porosity about 75–95% with a large amount of closed gas pockets and irregular porous structure. This material is usually used in the form of sandwich panels to achieve a higher absorption effect through uniform distribution of stress during loading. An alternative way to produce porous materials with precisely controlled shape of porous geometry is the SLM technology [9]. SLM uses a layer-based production which allows for the manufacturing of the porous material with a complex shape that can be designed directly for the Materials 2018, 11, 2129; doi:10.3390/ma11112129 www.mdpi.com/journal/materials
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