Lattice structures are porous patterns obtained by a controlled repetition in space of a designed unit cell, resulting in reduced weight and unique functional characteristics as high specific strength and stiffness, mechanical energy absorption and heat transfer control. Aim of this work is to tailor the geometrical variables to fabricate L-PBF Inconel 718 lattice structures in order to obtain the desired mechanical and microstructural properties. CAD models of different porous structures (cell type: FCC-Z) were developed varying geometrical parameters. FEM simulations were conducted to evaluate the results of 3D printing in terms of distortion and residual stresses. To analyse deformation and failure characteristics of the considered lattice structures, different tests were performed, including SEM characterization and CMM measurements. The as-built samples were then subjected to metallographic characterization to identify their microstructural characteristics and analyze the presence of defects. Through the micro-hardness tests, it was possible to evaluate the mechanical performance of the material. Heat treatments were carried out to investigate their effect on the mechanical and microstructural properties. In a subsequent phase of the research, the lattice structures initially examined were employed as supports for the internal channels of metallic components. The aim is to properly dissipate the heat generated during production, avoiding severe deformations. The latter could compromise the structural integrity of the component, reducing its functionality and compliance with project specifications. At the same time, it was crucial to identify the best density compromise of the lattice structures, a factor affecting their ease of removal during the post-processing phase through mechanical and/or chemical abrasion. Finite Element Method (FEM) simulations of the L-PBF process were conducted to assess the outcomes of 3D printing in terms of distortions and residual stresses. The simulation model was validated through a 3D scan of the component.
Le strutture reticolari sono strutture porose ottenute mediante una ripetizione controllata nello spazio 3D di una cella unitaria opportunamente progettata, con conseguente riduzione del peso e caratteristiche funzionali uniche come: alta resistenza specifica e rigidità, assorbimento di energia meccanica e controllo del trasferimento di calore. L'obiettivo di questo lavoro è quello di adattare le variabili geometriche per fabbricare, attraverso il processo L-PBF, provini in struttura reticolare in Inconel 718 al fine di ottenere le proprietà meccaniche e microstrutturali desiderate. Sono stati sviluppati modelli CAD di diverse strutture lattice (tipo di cella: FCC-Z) variando i parametri geometrici. Sono state condotte simulazioni FEM per valutare i risultati della stampa 3D in termini di distorsioni e tensioni residue. Per analizzare le caratteristiche di deformazione e rottura delle strutture reticolari, sono stati eseguiti diversi test, compresa la caratterizzazione SEM e le misurazioni tramite CMM. I campioni as-built sono stati successivamente sottoposti a caratterizzazione metallografica per identificarne le caratteristiche microstrutturali e analizzare la presenza di eventuali difetti. Attraverso i test di microdurezza è stato possibile valutare le prestazioni meccaniche del materiale. Sono stati eseguiti dei trattamenti termici per investigare il loro effetto sulle proprietà meccaniche e microstrutturali. In una fase successiva della ricerca, le strutture reticolari esaminate inizialmente sono state impiegate come supporti per i canali interni dei componenti metallici. L'obiettivo è dissipare in modo ottimale il calore generato durante la fase di produzione, evitando deformazioni indesiderate. Queste ultime potrebbero compromettere l'integrità strutturale del pezzo, riducendone la funzionalità e la conformità alle specifiche di progetto. Allo stesso tempo, è stato importante individuare il miglior compromesso di densità delle strutture reticolari, un fattore che incide sulla loro facilità di rimozione durante la fase di post-processing mediante abrasione meccanica e/o chimica. Le simulazioni FEM del processo L-PBF sono state condotte per valutare i risultati della stampa 3D in termini di distorsioni e tensioni residue. Tramite scansione 3D del componente è stato validato il modello di simulazione.
Analisi numerica e sperimentale di strutture lattice per l’ottimizzazione della tecnologia Laser Powder Bed Fusion / Santoni, Alberto. - (2024 Jun 17).
Analisi numerica e sperimentale di strutture lattice per l’ottimizzazione della tecnologia Laser Powder Bed Fusion
SANTONI, ALBERTO
2024-06-17
Abstract
Lattice structures are porous patterns obtained by a controlled repetition in space of a designed unit cell, resulting in reduced weight and unique functional characteristics as high specific strength and stiffness, mechanical energy absorption and heat transfer control. Aim of this work is to tailor the geometrical variables to fabricate L-PBF Inconel 718 lattice structures in order to obtain the desired mechanical and microstructural properties. CAD models of different porous structures (cell type: FCC-Z) were developed varying geometrical parameters. FEM simulations were conducted to evaluate the results of 3D printing in terms of distortion and residual stresses. To analyse deformation and failure characteristics of the considered lattice structures, different tests were performed, including SEM characterization and CMM measurements. The as-built samples were then subjected to metallographic characterization to identify their microstructural characteristics and analyze the presence of defects. Through the micro-hardness tests, it was possible to evaluate the mechanical performance of the material. Heat treatments were carried out to investigate their effect on the mechanical and microstructural properties. In a subsequent phase of the research, the lattice structures initially examined were employed as supports for the internal channels of metallic components. The aim is to properly dissipate the heat generated during production, avoiding severe deformations. The latter could compromise the structural integrity of the component, reducing its functionality and compliance with project specifications. At the same time, it was crucial to identify the best density compromise of the lattice structures, a factor affecting their ease of removal during the post-processing phase through mechanical and/or chemical abrasion. Finite Element Method (FEM) simulations of the L-PBF process were conducted to assess the outcomes of 3D printing in terms of distortions and residual stresses. The simulation model was validated through a 3D scan of the component.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
