Image-based numerical characterization and experimental validation of tensile behavior of octet-truss lattice structures

• Published in: Additive manufacturing Vol. 41; p. 101949
• Main Authors: Korshunova, N., Alaimo, G., Hosseini, S.B., Carraturo, M., Reali, A., Niiranen, J., Auricchio, F., Rank, E., Kollmannsberger, S.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.05.2021
• Subjects: Additive manufacturing; Computed tomography; Finite Cell Method; Finite Element method; Geometrical defects; Numerical homogenization; Octet-truss lattice; Octet-truss lattice; Computed tomography; Geometrical defects; Additive manufacturing; Finite Cell Method; Numerical homogenization; Finite Element method
• ISSN: 2214-8604; 2214-7810; 2214-7810
• DOI: 10.1016/j.addma.2021.101949

The production of lightweight metal lattice structures has received much attention due to the recent developments in additive manufacturing (AM). The design flexibility comes, however, with the complexity of the underlying physics. In fact, metal additive manufacturing introduces process-induced geometrical defects that mainly result in deviations of the effective geometry from the nominal one. This change in the final printed shape is the primary cause of the gap between the as-designed and as-manufactured mechanical behavior of AM products. Thus, the possibility to incorporate the precise manufactured geometries into the computational analysis is crucial for the quality and performance assessment of the final parts. Computed tomography (CT) is an accurate method for the acquisition of the manufactured shape. However, it is often not feasible to integrate the CT-based geometrical information into the traditional computational analysis due to the complexity of the meshing procedure for such high-resolution geometrical models and the prohibitive numerical costs. In this work, an embedded numerical framework is applied to efficiently simulate and compare the mechanical behavior of as-designed to as-manufactured octet-truss lattice structures. The parts are produced using laser powder bed fusion (LPBF). Employing an immersed boundary method, namely the Finite Cell Method (FCM), we perform direct numerical simulations (DNS) and first-order numerical homogenization analysis of a tensile test for a 3D printed octet-truss structure. Numerical results based on CT scan (as-manufactured geometry) show an excellent agreement with experimental measurements, whereas both DNS and first-order numerical homogenization performed directly on the 3D virtual model (as-designed geometry) of the structure show a significant deviation from experimental data. [Display omitted] •Incorporation of as-manufactured lattice geometries in numerical analysis is challenging.•Immersed methods allow to account for process-induced defects in an efficient image-to-numerical-characterization workflow.•Numerical experiments are performed directly on the CT images of octet-truss lattices.•As-manufactured results are validated through experimental measurements.