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Dipartimento di Ingegneria "Enzo Ferrari"

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2022 - Effective Mechanical Properties of AlSi7Mg Additively Manufactured Cubic Lattice Structures [Articolo su rivista]
Mantovani, Sara; Giacalone, Mauro; Merulla, Andrea; Bassoli, Elena; Defanti, Silvio

Lattice structures, whose manufacturing has been enabled by additive technologies, are gaining growing popularity in all the fields where lightweighting is imperative. Since the complexity of the lattice geometries stretches the technological boundaries even of additive processes, the manufactured structures can be significantly different from the nominal ones, in terms of expected dimensions but also of defects. Therefore, the successful use of lattices needs the combined optimization of their design, structural modeling, build orientation, and setup. The article reports the results of quasi-static compression tests performed on BCCxyz lattices manufactured in a AlSi7Mg alloy using additive manufacturing. The results are compared with numerical simulations using two different approaches. The findings show the influence of the relative density on stiffness, strength, and on the energy absorption properties of the lattice. The correlation with the technological feasibility points out credible improvements in the choice of a unit cell with fewer manufacturing issues, lower density, and possibly equal mechanical properties.

2022 - On the Technological Feasibility of additively manufactured self-supporting AlSi10Mg lattice structures [Articolo su rivista]
Bassoli, Elena; Mantovani, Sara; Giacalone, Mauro; Merulla, Andrea; Defanti, Silvio

The capability to design and manufacture metal lattice structures is today one of the most promising targets of Powder Bed Fusion technologies. Not only additively manufactured lattices offer great lightweighting possibilities, but they open the way to tailored and graded mechanical response. To best capitalize on this opportunity, research effort is first needed to assess the feasibility of reticular structures and to quantify the expected deviations from the nominal geometry, as a function of the cell topology and dimensions. Notwithstanding the inherent suitability of additive processes to complex shapes, this paper proposes a more exact definition of the technological boundaries for body-centred cubic lattices, showing to what extent specific dimensional ratios, as well as a self-supporting cell structure, can be favourable to minimize thedeviation from the nominal reticulum in terms of dimensions, density and presence of defects.

2022 - Shafts with U-shaped circumferential grooves: design charts for stress concentration factors, radial displacement and Poisson’s ratio influence [Articolo su rivista]
Mantovani, Sara; Chiari, Alessandro; Giacalone, Mauro; Strozzi, Antonio

Shafts with U-shaped circumferential grooves subjected to internal normal force and bending moment are investigated on the basis of finite element analysis. The classical problem of the Stress Concentration Factors (SCFs) identification is addressed. SCF charts are provided, adopting the maximum equivalent von Mises stress in the SCF definition. The discrepancy between the uniaxial SCFs extracted from the standard reference books and the multiaxial SCF obtained by finite element increases from 5% up to 20%. The intersections between the SCF curves are studied, which reveal a non-monotonic profile of the SCFs with respect to the outer and inner diameter ratio of the notched shaft. The radial displacement at the notch root is examined and design charts of ample validity and prompt access are compiled. It is found that the radial displacement sign and magnitude are largely dependent on the geometry of the notch. Furthermore, the strain and stress state of extremely shallow grooves are analysed and a critical discussion on their SCFs using the von Mises criterion is presented. The influence of the Poisson’s ratio is considered. A simplified method for the evaluation of a multiaxial SCF is proposed to account for the Poisson’s ratio effect. Thanks to the employment of few dedicated diagrams, the present method allows an accurate evaluation of the SCF for U-grooved shafts, when the Poisson’s ratio differs from the common 0.3 value.

2020 - Numerical-experimental correlation of dynamic test of a honeycomb impact attenuator for a formula sae vehicle [Articolo su rivista]
Vettorello, A.; Campo, G. A.; Goldoni, G.; Giacalone, M.

A honeycomb impact attenuator for a Formula SAE (FSAE) prototype vehicle is examined using both experimental and numerical analyses. Two common FSAE impact attenuators were compared to a new design concept, combining four layers of hexagonal honeycomb. The comparison aimed to obtain the combination of the lowest mass and highest energy absorption. The attenuator must comply with both the FSAE championship rules and further internally-defined design constraints. The work continues addressing the numerical-experimental correlation of the applied materials. Finally, the finite element models for virtual crash testing are presented and were validated through the experimental tests.

2020 - Steering column support topology optimization including lattice structure for metal additive manufacturing [Articolo su rivista]
Mantovani, S.; Campo, G. A.; Giacalone, M.

Structural engineering in the automotive industry has moved towards weight reduction and passive safety whilst maintaining a good structural performance. The development of Additive Manufacturing (AM) technologies has boosted design freedom, leading to a wide range of geometries and integrating functionally-graded lattice structures. This paper presents three AM-oriented numerical optimization methods, aimed at optimizing components made of: i) bulk material, ii) a combination of bulk material and graded lattice structures; iii) an integration of solid, lattice and thin-walled structures. The optimization methods were validated by considering the steering column support of a mid-rear engine sports car, involving complex loading conditions and shape. The results of the three methods are compared, and the advantages and disadvantages of the solutions are discussed. The integration between solid, lattice thin-walled structures produced the best results, with a mass reduction of 49.7% with respect to the existing component.