Numerical Modelling of DMLS Ti6Al4V(ELI) Polygon Structures

This study documents numerical modelling of different types of polygon structures. To reduce computation costs, planar and extruded Ti6Al4V(ELI) hexagonal shell structures were used to predict stresses in the out-of-plane and in-plane directions. Numerical modeling is especially useful for complex behavior analysis of structures. It is employed to forecast a structure's mechanical characteristics. Conversely, analytical modeling is based on mathematical equations that may not accurately reflect the geometry of the model, which limits its ability to anticipate behavior, especially that of structures. In such cases, numerical modelling is used for predicting structural bending, axial deformation, and buckling behaviour. In the present work, the hexagonal polygon was subjected to out-of-plane and in-plane uniaxial compression loads. This was done to compare the bending and buckling behaviour of finite element (FE) models to analytical models. The numerical and analytical results were then compared to determine how the ratio (t/L) of the wall thickness (t) and length of the polygon members (L) influenced the effective stiffness of the hexagonal polygon. Emphasis was placed on the analysis of buckling failure in the present work as it was shown here that for direct compression loading along the z-axis, lattice wall structures were more likely to fail under buckling than in direct deformation. Non-linear numerical analysis of buckling was adopted for use in the present work instead of linear numerical analysis in recognition of the fact that the latter method only identifies buckling modes, while the former also avails information about deformation. This then allows the investigation of possible failure of thin structures in buckling. The simulation for nonlinear analysis of buckling was run using the Johnson-Cook Model that is built into ABAQUS/CAE. The triangular polygon was seen to have the greatest load-bearing capacity and stiffness of all polygons that were modelled. The hexagonal model was observed to generate deformations due to compression, similar to those reported in the literature. The critical buckling loads for the analytical honeycomb (HC) models were found to be below the yield stress for (1-, 1.125-, and 1.25-mm wall thicknesses) and above the yield stress for all FE HC models, respectively. The effective stiffness of the HC models was observed to increase with the increasing (t/L) ratio, for both the numerical and analytical models. Future research should focus on experimentation for all of the different polygon structures computationally modelled in this work in order to confirm the obtained results.