Towards a fracture mechanics-based fatigue assessment of lattice structures obtained from additive manufacturing of metallic powders

Additive Manufacturing (AM) technologies are at the forefront of technological development in machine design as they allow the production of complex parts with high stiffness-to-weight ratios, such as lattice structures, that conventional production processes cannot manufacture. Despite the advantages of AM and lattice structures, their potential is currently limited by concerns related to their fatigue strength due to process-related intrinsic defects. Considering that fatigue is a leading cause of mechanical failures that require costly maintenance, the interest in understanding the fatigue strength of AMed lattice structures is evident. This work explores the applicability of the Linear Elastic Fracture Mechanics (LEFM) for predicting the fatigue limit of lattice structures, building on the positive results obtained for AMed fully-dense materials. It includes a literature review of the experimental fatigue analysis of lattice structures, highlighting the experimental evidence of the fundamental role of AM defects and notches on the fatigue strength of AMed lattice structures. The main conclusions are that AMed lattice structures should be considered defective and notched materials, and the fatigue assessment should be performed with LEFM-based approaches. Lastly, this paper validates LEFM-based predictions against 400+ experimental data for AMed materials from the literature, including small-sized specimens and lattice structures.