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EMANUELE TOGNOLI

Ricercatore t.d. art. 24 c. 3 lett. A
Dipartimento di Ingegneria "Enzo Ferrari"

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Pubblicazioni

2024 - Dimensional and Mechanical Assessment of Gyroid Lattices Produced in Aluminum by Laser Powder Bed Fusion [Relazione in Atti di Convegno]
Defanti, Silvio; Giacalone, Mauro; Mantovani, Sara; Tognoli, Emanuele
abstract

The study investigates the use of aluminum gyroid lattices for structural purposes, with a particular focus on feasibility, dimensional accuracy, and compressive load performance. Gyroid lattice samples were built using laser powder bed fusion technology with AlSi10Mg, utilizing cell sizes of 6, 8, and 12 mm and a wall thickness of 0.5 mm. The compression performance of the samples was tested. The study revealed differences in dimensional accuracy in different directions, which was attributed to the fabrication process. All samples were heavier than expected, with additional materials being proportional to cell size. However, the samples exhibited high compressive strength and stiffness, indicating their potential use in load-bearing applications.

2024 - Dimensional and mechanical assessment of gyroid lattices produced in aluminum by laser powder bed fusion [Articolo su rivista]
Defanti, Silvio; Giacalone, Mauro; Mantovani, Sara; Tognoli, Emanuele
abstract

2024 - Features of Vat-Photopolymerized Masters for Microfluidic Device Manufacturing [Articolo su rivista]
Gatto, M. L.; Mengucci, P.; Mattioli-Belmonte, M.; Munteanu, D.; Nasini, R.; Tognoli, E.; Denti, L.; Gatto, A.
abstract

The growing interest in advancing microfluidic devices for manipulating fluids within micrometer-scale channels has prompted a shift in manufacturing practices, moving from single-component production to medium-size batches. This transition arises due to the impracticality of lab-scale manufacturing methods in accommodating the increased demand. This experimental study focuses on the design of master benchmarks 1–5, taking into consideration critical parameters such as rib width, height, and the relative width-to-height ratio. Notably, benchmarks 4 and 5 featured ribs that were strategically connected to the inlet, outlet, and reaction chamber of the master, enhancing their utility for subsequent replica production. Vat photopolymerization was employed for the fabrication of benchmarks 1–5, while replicas of benchmarks 4 and 5 were generated through polydimethylsiloxane casting. Dimensional investigations of the ribs and channels in both the master benchmarks and replicas were conducted using an optical technique validated through readability analysis based on the Michelson global contrast index. The primary goal was to evaluate the potential applicability of vat photopolymerization technology for efficiently producing microfluidic devices through a streamlined production process. Results indicate that the combination of vat photopolymerization followed by replication is well suited for achieving a minimum rib size of 25 µm in width and an aspect ratio of 1:12 for the master benchmark.

2024 - High-temperature tensile behavior of AlSi7Mg parts built by LPBF under high-productivity conditions [Articolo su rivista]
Bassoli, E.; Tognoli, E.; Defanti, S.
abstract

As additive manufacturing of metals gains traction for demanding applications, more comprehensive material cards covering mechanical response across a broader spectrum of operating conditions are needed. The integration of additive manufacturing into industries that rely on aluminum alloys, notably automotive and aerospace, underscores the imperative of a profound comprehension of how these materials respond to mechanical loading at elevated temperatures. Such insights are not only important for powertrain components but also for parts that combine structural and functional purposes, such as heat exchangers. At the same time, automotive applications need to target the production of large parts with sufficiently high productivity. This study addresses the intricate interplay between microstructural evolution, plastic deformation and mechanical response of AlSi7Mg parts fabricated by laser powder bed fusion under high-productivity conditions, spanning a testing temperature range of 25-300 degrees C. Above 150 degrees C, a significant decrease in proof and tensile strength is measured, accompanied by localized necking and the formation of dimples on the rupture surfaces. At 300 degrees C, the pronounced plasticization leads to yielding and failure at stress values 30-40% lower than at room temperature, with triple ductility. Work-hardening coefficients were calculated to describe the plastic regime. Furthermore, an investigation into density, hardness, microstructure, and fracture surfaces was conducted to corroborate the mechanical response. The outcomes enabled the quantification of mechanical property variations across the 6 temperature intervals, thereby constructing a map that empowers industry to unlock the full potential of additive manufacturing aluminum alloys.

2023 - Beads for Cell Immobilization: Comparison of Alternative Additive Manufacturing Techniques [Articolo su rivista]
Gatto, M. L.; Mengucci, P.; Munteanu, D.; Nasini, R.; Tognoli, E.; Denti, L.; Gatto, A.
abstract

The attachment or entrapment of microbial cells and enzymes are promising solutions for various industrial applications. When the traps are beads, they are dispersed in a fluidized bed in a vessel where a pump guarantees fresh liquid inflow and waste outflow without washing out the cells. Scientific papers report numerous types of cell entrapment, but most of their applications remain at the laboratory level. In the present research, rigid polymer beads were manufactured by two different additive manufacturing (AM) techniques in order to verify the economy, reusability, and stability of the traps, with a view toward a straightforward industrial application. The proposed solutions allowed for overcoming some of the drawbacks of traditional manufacturing solutions, such as the limited mechanical stability of gel traps, and they guaranteed the possibility of producing parts of constant quality with purposely designed exchange surfaces, which are unfeasible when using conventional processes. AM proved to be a viable manufacturing solution for beads with complex shapes of two different size ranges. A deep insight into the production and characteristics of beads manufactured by AM is provided. The paper provides biotechnologists with a manufacturing perspective, and the results can be directly applied to transit from the laboratory to the industrial scale.

2023 - Improved biomechanical behavior of 316L graded scaffolds for bone tissue regeneration produced by laser powder bed fusion [Articolo su rivista]
Gatto, Maria Laura; Cerqueni, Giorgia; Groppo, Riccardo; Santecchia, Eleonora; Tognoli, Emanuele; Defanti, Silvio; Mattioli-Belmonte, Monica; Mengucci, Paolo
abstract

Graded lattice scaffolds based on rhombic dodecahedral (RD) elementary unit cell geometry were manufactured in 316L stainless steel (SS) by laser powder bed fusion (LPBF). Two different strategies based on varying strut thickness layer-by-layer in the building direction were adopted to obtain the graded scaffolds: a) decreasing strut size from core to edge to produce the dense-in (DI) structure and b) increasing strut size in the same direction to produce the dense-out (DO) structure. Both graded structures (DI and DO) were constructed with specular symmetry with respect to the central horizontal axis. Structural, mechanical, and biological characterizations were carried out to evaluate feasibility of designing appropriate biomechanical performances of graded scaffolds in the perspective of bone tissue regeneration. Results showed that mechanical behavior is governed by graded geometry, while printing parameters influence structural properties of the material such as density, textures, and crystallographic phases. The predominant failure mechanism in graded structures initiates in correspondence of thinner struts, due to high stress concentrations on strut junctions. Biological tests evidenced better proliferation of cells in the DO graded scaffold, which in turn exhibits mechanical properties close to cortical bone. The combined control of grading strategy, printing parameters and elementary unit cell geometry can enable implementing scaffolds with improved biomechanical performances for bone tissue regeneration.

2023 - Influence of Trabecular Geometry on Scaffold Mechanical Behavior and MG-63 Cell Viability [Articolo su rivista]
Gatto, Maria Laura; Cerqueni, Giorgia; Furlani, Michele; Riberti, Nicole; Tognoli, Emanuele; Denti, Lucia; Leonardi, Francesco; Giuliani, Alessandra; Mattioli-Belmonte, Monica; Mengucci, Paolo
abstract

In a scaffold-based approach for bone tissue regeneration, the control over morphometry allows for balancing scaffold biomechanical performances. In this experimental work, trabecular geometry was obtained by a generative design process, and scaffolds were manufactured by vat photopolymerization with 60% (P60), 70% (P70) and 80% (P80) total porosity. The mechanical and biological performances of the produced scaffolds were investigated, and the results were correlated with morphometric parameters, aiming to investigate the influence of trabecular geometry on the elastic modulus, the ultimate compressive strength of scaffolds and MG-63 human osteosarcoma cell viability. The results showed that P60 trabecular geometry allows for matching the mechanical requirements of human mandibular trabecular bone. From the statistical analysis, a general trend can be inferred, suggesting strut thickness, the degree of anisotropy, connectivity density and specific surface as the main morphometric parameters influencing the biomechanical behavior of trabecular scaffolds, in the perspective of tissue engineering applications.

2023 - On the Biomechanical Performances of Duplex Stainless Steel Graded Scaffolds Produced by Laser Powder Bed Fusion for Tissue Engineering Applications [Articolo su rivista]
Gatto, M. L.; Cerqueni, G.; Groppo, R.; Tognoli, E.; Santoni, A.; Cabibbo, M.; Mattioli-Belmonte, M.; Mengucci, P.
abstract

This experimental study aims to extend the know-how on biomechanical performances of duplex stainless steel (DSS) for tissue engineering applications to a graded lattice geometry scaffold based on the F53 DSS (UNS S32750 according to ASTM A182) produced by laser powder bed fusion (LPBF). The same dense-out graded geometry based on rhombic dodecahedral elementary unit cells investigated in previous work on 316L stainless steel (SS) was adopted here for the manufacturing of the F53 DSS scaffold (SF53). Microstructural characterization and mechanical and biological tests were carried out on the SF53 scaffold, using the in vitro behavior of the 316L stainless steel scaffold (S316L) as a control. Results show that microstructure developed as a consequence of different volume energy density (VED) values is mainly responsible for the different mechanical behaviors of SF53 and S316L, both fabricated using the same LPBF manufacturing system. Specifically, the ultimate compressive strength (σUC) and elastic moduli (E) of SF53 are three times and seven times higher than S316L, respectively. Moreover, preliminary biological tests evidenced better cell viability in SF53 than in S316L already after seven days of culture, suggesting SF53 with dense-out graded geometry as a viable alternative to 316L SS for bone tissue engineering applications.

2022 - An investigation on the processing conditions of Ti-6Al-2Sn-4Zr-2Mo by electron beam powder bed fusion: Microstructure, defect distribution, mechanical properties and dimensional accuracy [Articolo su rivista]
Galati, M.; Defanti, S.; Saboori, A.; Rizza, G.; Tognoli, E.; Vincenzi, N.; Gatto, A.; Iuliano, L.
abstract

2022 - Boosting Productivity of Laser Powder Bed Fusion for AlSi10Mg [Articolo su rivista]
Defanti, S; Cappelletti, C; Gatto, A; Tognoli, E; Fabbri, F
abstract

The Laser Powder Bed Fusion (L-PBF) process is recognized for high-end industrial applications due to its ability to produce parts with high geometric complexity. If lightweighting is one of the main strengths of L-PBF, a weakness is still the trade-off between high mechanical properties and competitive productivity. This objective can be targeted through a fine tuning of the process parameters within the manufacturing window. The paper pursues the combined optimization of part quality and process productivity for AlSi10Mg by going beyond the commonly used approach based solely on volumetric energy density. The effects of hatch distance and scan speed on the two targets were analyzed in detail. The best results were achieved by the adoption of a high scan speed and a low hatch distance, with notably different outcomes for nearly the same energy density.

2021 - Design for additive manufacturing and for machining in the automotive field [Articolo su rivista]
Bassoli, E.; Defanti, S.; Tognoli, E.; Vincenzi, N.; Esposti, L. D.
abstract

High cost, unpredictable defects and out-of-tolerance rejections in final parts are preventing the complete deployment of Laser-based Powder Bed Fusion (LPBF) on an industrial scale. Repeatability, speed and right-first-time manufacturing require synergistic design approaches. In addition, post-build finishing operations of LPBF parts are the object of increasing attention to avoid the risk of bottlenecks in the machining step. An aluminum component for automotive application was redesigned through topology optimization and Design for Additive Manufacturing. Simulation of the build process allowed to choose the orientation and the support location for potential lowest deformation and residual stresses. Design for Finishing was adopted in order to facilitate the machining operations after additive construction. The optical dimensional check proved a good correspondence with the tolerances predicted by process simulation and confirmed part acceptability. A cost and time comparison versus CNC alone attested to the convenience of LPBF unless single parts had to be produced.

2020 - Effect of shot peening conditions on the fatigue life of additively manufactured A357.0 parts [Articolo su rivista]
Gatto, A.; Sola, A.; Tognoli, E.
abstract

Fatigue performance can be a critical attribute for the production of structural parts or components via additive manufacturing (AM). In comparison to the static tensile behavior of AM components, there is a lack of knowledge regarding the fatigue performance. The growing market demand for AM implies the need for more accurate fatigue investigations to account for dynamically loaded applications. A357.0 parts are processed by laser-based powder bed fusion (L-PBF) in order to evaluate the effect of surface finishing on fatigue behavior. The specimens are surface finished by shot peening using φ = 0.2 and φ = 0.4 mm steel particles and φ = 0.21-0.3 mm zirconia-based ceramic particles. The investigation proves that all the considered post-processing surface treatments increase the fatigue resistance of as-built parts, but the effect of peening with φ = 0.4 mm steel particles or with ceramic particles is more pronounced than that of peening with φ = 0.2 mm steel particles, although this treatment has the same Almen A value as the ceramic one. The surface morphology and the crack surface of the samples are also investigated.

2019 - Effect of Three Different Finishing Processes on the Surface Morphology and Fatigue Life of A357.0 Parts Produced by Laser‐Based Powder Bed Fusion [Articolo su rivista]
Gatto, Andrea; Bassoli, Elena; Denti, Lucia; Sola, Antonella; Tognoli, Emanuele; Comin, Andrea; Porro, Juan Antonio; Cordovilla, Francisco; Angulo, Ignacio; Ocaña, Jose Luis
abstract

A357.0 parts are processed by laser-based powder bed fusion and surface finished via plastic media blasting, ceramic sand blasting, and laser shock processing. The morphological analysis proves that plastic media blasting causes the most effective peak removal, the most efficient decrease in valley depth, and the greatest reduction in surface roughness. All the surface finishing processes enhance the fatigue life, however ceramic sand blasting bring about the greatest increase in the value of σmax for an infinite fatigue life limit of 2106 cycles. The experimental results suggest therefore that the infinite fatigue life value is more sensitive to the residual stress state engendered by ceramic sand blasting than to the reduction in surface roughness. Breakthrough cracks start at the interface between crushed or modified surface particles and the underlying macro-surface. However, at a distance of a few hundred microns from the crack initiation point, the fracture surface morphology become cellular for all the specimens.

2018 - Fatigue behavior of as-built L-PBF A357.0 parts [Articolo su rivista]
Bassoli, Elena; Denti, Lucia; Comin, Andrea; Sola, Antonella; Tognoli, Emanuele
abstract

Laser-based powder bed fusion (L-PBF) is nowadays the preeminent additive manufacturing (AM) technique to produce metal parts. Nonetheless, relatively few metal powders are currently available for industrial L-PBF, especially if aluminum-based feedstocks are involved. In order to fill the existing gap, A357.0 (also known as A357 or A13570) powders are here processed by L-PBF and, for the first time, the fatigue behavior is investigated in the as-built state to verify the net-shaping potentiality of AM. Both the low-cycle and high-cycle fatigue areas are analyzed to draw the complete Wohler diagram. The infinite lifetime limit is set to 2 × 106stress cycles and the staircase method is applied to calculate a mean fatigue strength of 60 MPa. This value is slightly lower but still comparable to the published data for AlSi10Mg parts manufactured by L-PBF, even if the A357.0 samples considered here have not received any post-processing treatment.