A novel methodology for the prediction of the stress–strain response of laser powder bed fusion lattice structure based on a multi-scale approach

Additive manufacturing (AM), and in particular laser powder bed fusion (LPBF), is a technology that allows to easily produce geometrically complex structural components. Among others, an example is represented by lattice structures which allow to obtain lightweight components with enhanced mechanical properties. Despite a large number of papers available in the literature, mechanical behavior of lattice structures made by LPBF is still difficult to predict, due to microstructure modifications induced by their small features, scanning strategy and building direction. In this regard, a multi-scale approach to predict the effective response within the lattice structure is proposed in this investigation. It mainly consists in local measurements by nano-indentation tests, carried out at different portion of the lattice structure and along different orientation to build the effective constitutive response of the component. In this way, possible modifications induced by the LPBF process within the microstructure can be captured. Relying on experimental investigations at both macro and nano-scale, a numerical model for stainless steel 316L octet-truss lattice specimen has been calibrated. To improve the accuracy of the simulations, the geometrical model was built starting from the real geometry of the component through micro-CT images. Obtained results revealed that using the as-built geometry and effective local properties is fundamental for an accurate prediction of the mechanical behavior of lattice structures made by LPBF manufacturing process.