Deformation behaviour of stainless steel microlattice structures by selective laser melting

Recent developments in selective laser melting (SLM) have enabled the fabrication of microlattice structures with periodic unit cells: a potential sandwich core material for energy dissipation. In this study, a full scale 3D finite element (FE) model was developed to investigate the macroscopic deformation of microlattice structures and the microscopic stress and strain evolution in the solid struts of the microlattice. The constitutive behaviour of SLM stainless steel 316L, the parent material of microlattice, was accurately characterised using non-contacting imaging techniques and input to the developed FE model, which was then validated by uniaxial compression experiments. It was found that local plastic stress and strain evolve near the nodal joint, thus forming a plastic hinge, whilst the majority of the strut remains elastic. The localised plastic stress/strain and the volume of plastic zone increase with the compression of the microlattice, resulting in the nearly plateau region with slight linear hardening in the stress−strain curve. The final densification process is dominated by the self-contact interaction among struts in the microlattice. Finally, the FE predictions reveal that the deformation of a microlattice is significantly affected by applied boundary conditions and constitutive properties of SLM parent materials such as Young׳s modulus.