Mechanical behaviour and damage assessment of AlSi10Mg lattice structures fabricated by laser powder bed fusion under static and fatigue loading

The monotonic and fatigue mechanical behaviour of diamond cell lattice structures fabricated by Laser Powder Bed Fusion (L-PFB) from Al10SiMg powder with two relative densities (∼40 and 50 %) was investigated. Pseudostatic tensile, compression and cyclic uniaxial loading tests were carried out with stress ratios R of 0.1 (pull-pull), 10 (push-push) and −1 (symmetric pull-push). The lattice specimens' design incorporated fully dense end regions to facilitate clamping and enable the application of both tensile and compressive loads. Furthermore, smooth graded transitions between the central region of constant relative density and the fully dense extremities were implemented to mitigate stress concentration effects during cyclic loading. The study included measurements of the Young's modulus, the yielding behaviour, the strength, the ductility and the fracture characteristics, and involved a comparison between the tensile and compression monotonic test results, including the collapse and crush patterns associated with the tests. The fatigue test results were then used to analyze damage accumulation over the specimens' lifetimes as indicated by the measured strain response, which exhibited a three-stage pattern. Subsequently, S-N diagrams were built as a function of the global stress amplitude and global maximum stress applied. A novel local stress parameter, encompassing the maximum normal and shear stresses, was proposed as an alternative method for rationalizing fatigue data for lattice structures. This comprehensive investigation provides insight into the mechanical performance and fatigue characteristics of diamond cell lattice structures under various loading conditions.