2D numerical simulation of auxetic metamaterials based on global DIC

Abstract

This work discusses a novel approach to simulate metallic auxetic structures manufactured via Selective Laser Melting (SLM). SLMmanufactured metamaterials are difficult to simulate accurately based on nominal geometry and bulk material behaviour. The geometry after printing is different from the nominal CAD geometry. Artefacts due to the printing process such as pores yield a material behaviour which depends on the surface/volume ratio. We investigate a phenomenological approach to obtain a simulation model calibrated with experimental data and Digital Image Correlation (DIC). Finite Element based global DIC as suggested by Hild [1,2] allows for obtaining accurate displacement fields, consistent with the true deformation of the lattice structure. Based on the nominal CAD geometry, a simplified parametrized simulation model is created, exploiting the abundant symmetries of lattice structures. Using nodal displacements from DIC in combination with the expected forces from an experiment, the model is calibrated via LS-OPT. The approach is applied to an antitetrachiral, auxetic structure. Furthermore, we discuss the accuracy of the approach, its applicability to other structures and possible extension into 3D space.