Evaluating quasi-static and fatigue performance of IN718 gyroid lattice structures fabricated via LPBF: Exploring relative densities

Abstract

Additive manufacturing (AM) technology has unlocked the possibilities of fabricating complex structures of components such as lattice structures. Based on the literature review, the significance of the thickness effect on lattice structures has not been completely investigated yet. Therefore, this research aims to study the wall thickness effect on the mechanical performance of sheet-based lattice structures under quasi-static compression and fatigue loading conditions. For this aim, four geometries of lattice structures with designed relative densities of 12.5%, 25.0%, 37.5%, and 50.0% were fabricated via Laser Powder Bed Fusion (LPBF) process using Inconel alloy 718. The specimens were heat-treated to eliminate residual stresses and then tested under monotonic and cyclic compressive loading conditions to obtain the mechanical responses for each respective relative density. The experimental results from the quasi-static and fatigue compression tests on different geometries were compared and analyzed with the use of Scanning Electron Microscopy (SEM) to observe the fatigue failure locations and their dependency on the surface morphology of those failure locations. In addition, the actual relative densities were also calculated to evaluate the geometrical deviations and correct the experimental results. Overall, the experimental data revealed that there are strong associations between the lattices with various wall thicknesses and corresponding quasi-static and fatigue performance.