Investigation of mechanical and fatigue properties of lattice structure in AlSi7Mg

The first part of this work aim to evaluate the geometrical and final quality of lattice structures produced through Selective Laser Melting (SLM),furthermore the entire production process from design stage to finite product stage will be briefly described. To evaluate those results many measurement instruments were involved, such as caliber, optical microscopes and Tomography. The second part of this thesis investigate the static and fatigue behavior of an Aluminum-based alloy used in SLM processes, the aim is to evaluate the tensile behavior of the material and fatigue limit of post-processed and "as built" material. Three point bending tests are been chosen to estimate the fatigue limit , moreover these test point out the influence of "as built" surface roughness on fatigue performaces. The third part of this work is dedicated to the investigation of mechanical properties of Lattice Structures; three main types of lattice structure (BCC, FCC-L and HC at 45°) specimen were chosen and printed to evaluate static and fatigue properties, the results were compared to elastic FEA trying to find correlations between analytical model and the experimental results. Specimens were designed and produced in the AddMe Lab of the Politecnico of Milano using a Renishaw 250AM.

Questa tesi approccia da un punto di vista sperimentale le strutture trabecolari. Il lavoro si sviluppa partendo da un'analisi qualitativa e quantitativa delle geometrie effettivamente ottenute attraverso Selective Laser Melting, per poi articolarsi nella caratterizzazione delle proprietà meccaniche, sia statiche che a fatica, della lega di alluminio utilizzata (AlSi7Mg) e di alcune strutture trabecolari. In particolare modo verrà evidenziato l'effetto della finitura superficiale di questo processo sul limite di fatica del materiale. I trabecoli considerati saranno Body Centered Cubic, Face Centered Cubic e Holed Cube inclinata a 45°. Al fine di ispezionare i campioni sono stati impiegati microscopi ottici, SEM e tomografie. Le celle sono poi state modellate tramite analisi ad elementi finiti per individuare correlazioni tra il modello virtuale e i risultati sperimentali. I provini sono stati realizzati nei laboratori del Politecnico di Milano (Add.Me lab) usando una Renishaw250AM.