Wire-and-Arc Additive Manufacturing for lattice steel structures: overview of the experimental characterization on dot-by-dot rods

With the advent of a new arc-based additive manufacturing (AM) process, referred to as Wire-and-Arc Additive Manufacturing (WAAM), the scale of the metal printed parts increased up to several meters, thus becoming suitable for large-scale applications in marine, aerospace and construction sectors. However, specific considerations in terms of geometrical and mechanical properties ought to be made in order to effectively use the printed outcomes for structural engineering purposes. The introduction of the novel printing strategy referred to as “dot-by-dot”, consisting in successive drops of molten metal, enabled the use of WAAM to realize complex lattice structures, made by continuous grids of WAAM rods. Nevertheless, their proper design requires an accurate evaluation of the influence of the non-negligible inherent geometrical irregularities on the mechanical response of the rods. Hence, extensive experimental work is needed in order to evaluate the mechanical response of “dot-by-dot” WAAM rods with geometrical imperfections. The present study focuses on the mechanical characterization of dot-by-dot WAAM-produced 304L stainless steel intersected rods, constituting the basic units of grid and lattice structures. The mechanical response of the specimens is assessed through tensile experimental tests conducted on two-ways planar nodes obtained from the intersection of two rods with different angles, hereafter also refereed to as crossed rods. The experimental results are then compared with tensile tests on single rods, to quantify the influence of the intersection angle in the structural response of the lattice structures.