A multiscale-based methodology for the fatigue failure analysis of additively manufactured lattice structures applied to the four-point-bending test

The utilization of lattice structures has become increasingly widespread across various technological applications, encompassing both functional structures and materials designed for structural integrity. These structures are extensively employed in biomedical engineering, aerospace, and automotive industries, as well as in heat exchangers and thermal management systems. Recent research on the integration of lattice structures into primary load-bearing components, particularly in aerostructures, is gaining prominence. Specifically, fatigue resistance is one of the most critical requirements for materials intended for structural applications, and this is particularly valid for aerostructures, where standards are more rigorous and severe. In this study, a fatigue failure analysis methodology specifically developed for lattice structures is applied to a 316L steel lattice beam subjected to four-point bending under fully reversed loading. The proposed methodology employes different techniques both related to metamaterials and conventional analysis of structures subjected to alternate cyclic loads: homogenization, a technique largely used to synthetize mechanical properties of multi-phase repetitive structures, allows the model to be computationally efficient. Classical multi-axial Sines fatigue criterion has been used to compute the equivalent stress state of the critical de-homogenized lattice cell. The investigation also includes experimental validation tests and a comparative analysis of the results with existing literature data.