Experimental and numerical mechanical characterization of additively manufactured Ti6Al4V lattice structures considering progressive damage

Journal
International journal of mechanical sciences  
Volume
189
Article Number
105986
Citation
International Journal of Mechanical Sciences (189): 105986 (2021-01-01)
Publisher DOI
10.1016/j.ijmecsci.2020.105986
Scopus ID
2-s2.0-85092003799
The rapid progress in additive manufacturing enables the generation of complex structures that can be customized according to the application. For instance, lattice structures show potential in medical and lightweight applications as their mechanical properties can be scaled by the volume fraction of the cells according to the local requirements given by the load paths. In order to use lattice structures in design of structural parts, the mechanical properties need to be characterized. Due to the complex nature of the selective laser melting process, manufacturing imperfections as well as the microstructure play an important role and their effects can differ depending on volume fraction, building direction and especially load case (tension and compression). The aim of this study is to analyze these effects. In addition, a deeper understanding of the failure process is necessary which is gained by 3D digital image correlation and finite element simulations incorporating progressive damage. We found that surface defects are larger for horizontal struts printed directly on the powder bed and thus show a higher influence for specimens where building and loading direction are not aligned. Moreover, porosity leads to significantly different mechanical properties contingent on the load case. Depending on the volume fraction, different failure modes are observed which are captured and explained by finite element simulations allowing to avoid stress concentrations or undesired buckling in future designs. Finally, simulations of lattice structures are compared to computationally inexpensive simulations of unit cells with periodic boundary conditions. Good agreement is found and further insights into the influence of the load introduction are gained.
Subjects
3D printing
Compression
Finite element modelling
Periodic boundary conditions
Selective laser melting
Tension