Effect of additive manufactured lattice defects on mechanical properties: an automated method for the enhancement of lattice geometry

Metal additive manufacturing (MAM) enables the fabrication of structures with complexity and resolution that cannot be achieved by traditional manufacturing techniques, including lattice structures. However, MAM processes inherently induce local manufacturing defects, resulting in variation between the idealised and as-manufactured geometry and potentially introducing stress concentrations that are detrimental to structural performance. Quantification of these effects on mechanical performance enables the manipulation of intended lattice geometry to enhance structural performance. However, due to the geometric complexity and small scale of geometric defects, experimental testing and numerical simulation of lattice structures are technically difficult and time-consuming. To overcome this limitation, a novel methodology for quantifying the effect of manufacturing defects on the mechanical properties of MAM lattice structural elements is proposed. This method involves the automated analysis of microscope images of as-manufactured lattice structures to generate numerical models that automate the identification of plastic hinge behaviour in node elements based on custom MAM material properties. This method is applied to Ti-6Al-4V lattice structures fabricated by selective laser melting (SLM) with a range of strut and node diameters and cell sizes. This novel method is shown to predict the effect of local manufacturing defects on bulk lattice mechanical response and provides an efficient tool for the optimisation of as-manufactured MAM lattice structures.