Simulation and optimization of the load introduction geometry of additively manufactured lattice structure specimens

Additively manufactured lattice structures show potential in medical and lightweight applications due to scalability of mechanical properties by the relative density of the cells. This requires characterization of the effective mechanical properties. Often compressive tests are used, however, tensile tests are conducted rarely despite their physical relevance. Current studies show challenges especially in determining reliable values of the effective tensile strength since specimens often fail at the transition from load introduction to lattice structure. The goal of this contribution is to provide guidelines for constructing load introduction geometries leading to failure of the samples within the lattice structure. To optimize the load introduction geometry, nonlinear finite element simulations are performed to identify stress concentrations. Tensile, compressive and single-edge-notch bending experiments of the stereolithography manufactured base material are conducted to calibrate the material model. The simulations show that confined transversal contraction is problematic and that a smooth transition with decreasing relative density of the lattice cells seems promising to determine reliable effective mechanical properties. To validate the simulations, tensile tests of lattice structure specimens with 3D digital image correlation are conducted.

Subjects

Digital image correlation

Finite element method

Lattice structure

Stereolithography

Tensile test

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Simulation and optimization of the load introduction geometry of additively manufactured lattice structure specimens