  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.
