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Alessia Teresa Silvestri

Other affiliations: University of Bergamo
Bio: Alessia Teresa Silvestri is an academic researcher from University of Naples Federico II. The author has contributed to research in topics: Materials science & Selective laser melting. The author has an hindex of 5, co-authored 19 publications receiving 50 citations. Previous affiliations of Alessia Teresa Silvestri include University of Bergamo.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the results of the preliminary tests carried out by means of the FBM technology in which an external contribution of rotational speed of the samples was introduced, in order to increase the relative speed and energy dissipation between the parts and the fluidised abrasive particles, with the aim to increase process efficiency in terms of surface roughness reduction.

30 citations

Proceedings ArticleDOI
02 Jul 2019
TL;DR: In this article, the influence of the impact angle has been investigated by conducting experiments with AlSi10Mg plates made by Selective Laser Melting Technology (SLM), and the fluidized bed operated in bubbling fluidization regime.
Abstract: Additive Manufacturing (AM) can be considered today as a real production technology, which allows to realize parts with a complexity degree that, in some cases, is not achievable otherwise. However, one of the most relevant weak spots is the high surface roughness, especially for metal parts, making necessary the adoption of post-process finishing treatments. This paper deals with the preliminary investigations on the Fluidised Bed Machining (FBM) technology, in which a sample is dipped into a fluidized bed, i.e. a two-phase system where an abrasive, kept in motion through a gas, behaves like a fluid performing a huge number of impacts on the considered surface. This peculiarity could guarantee a high degree of homogeneity of the treated surface morphology. The influence of the impact angle has been investigated by conducting experiments with AlSi10Mg plates made by Selective Laser Melting Technology (SLM), and the fluidized bed operated in bubbling fluidization regime. The treatment has been carried out by dipping the samples for a total time of 3 hours and monitoring the results with a step of 30 min for the first 2 hours. The treated surfaces have been characterized by means of Confocal Microscopy and Scanning Electron Microscopy (SEM). Weight loss measurements have been carried out as well for a preliminary evaluation of wear. Results suggest a poor decrease in surface roughness (Sa), as also demonstrated by the poor weight loss, both due to a low impact energy of the abrasives. However, variations of other surface texture parameters (Sz, Ssk, Sku, Rdq), as well as SEM images, suggest that the main surface-abrasive flow interaction phenomena are micro-ploughing and micro-peening.Additive Manufacturing (AM) can be considered today as a real production technology, which allows to realize parts with a complexity degree that, in some cases, is not achievable otherwise. However, one of the most relevant weak spots is the high surface roughness, especially for metal parts, making necessary the adoption of post-process finishing treatments. This paper deals with the preliminary investigations on the Fluidised Bed Machining (FBM) technology, in which a sample is dipped into a fluidized bed, i.e. a two-phase system where an abrasive, kept in motion through a gas, behaves like a fluid performing a huge number of impacts on the considered surface. This peculiarity could guarantee a high degree of homogeneity of the treated surface morphology. The influence of the impact angle has been investigated by conducting experiments with AlSi10Mg plates made by Selective Laser Melting Technology (SLM), and the fluidized bed operated in bubbling fluidization regime. The treatment has been carried out ...

29 citations

Journal ArticleDOI
TL;DR: The role of the process parameters under a fixed energy density in Electron Beam Melting of Ti6Al4V was investigated in this article, where the beam current, scan speed and line offset were varied in a wide range keeping constant the energy density achieved.

29 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigate the mechanical properties of AlSi10Mg components produced with different SLM machines: EOS M400, SLM 280 and RENISHAW AM400.

23 citations

Journal ArticleDOI
TL;DR: In this paper, the authors deal with 3D printing composites fabricated by Continuous Fiber/Filament Fabrication with an innovative thermoplastic matrix infilled with micro carbon fiber, i.e., Onyx, and...
Abstract: This research activity deals with 3D printing composites fabricated by Continuous Fiber/Filament Fabrication with an innovative thermoplastic matrix infilled with microcarbon fiber, i.e., Onyx, and...

20 citations


Cited by
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Journal ArticleDOI
TL;DR: The current state-of-the-art metal additive manufacturing (AM) process still cannot meet the high industry requirements in terms of surface roughness as discussed by the authors, and there are limited ISO/ASTM standa...
Abstract: The current state-of-the-art metal additive manufacturing (AM) process still cannot meet the high industry requirements in terms of surface roughness. In addition, there are limited ISO/ASTM standa...

75 citations

Journal ArticleDOI
TL;DR: This paper presents a comprehensive review of the latest research carried out in understanding the mechanical properties of aluminium alloys processed by SLM under static, dynamic, different build orientations, and heat treatment conditions with the aim of identifying research gaps and future research directions.
Abstract: Selective laser melting (SLM) is a powder bed fusion type metal additive manufacturing process which is being applied to manufacture highly customised and value-added parts in biomedical, defence, aerospace, and automotive industries. Aluminium alloy is one of the widely used metals in manufacturing parts in SLM in these sectors due to its light weight, high strength, and corrosion resistance properties. Parts used in such applications can be subjected to severe dynamic loadings and high temperature conditions in service. It is important to understand the mechanical response of such products produced by SLM under different loading and operating conditions. This paper presents a comprehensive review of the latest research carried out in understanding the mechanical properties of aluminium alloys processed by SLM under static, dynamic, different build orientations, and heat treatment conditions with the aim of identifying research gaps and future research directions.

74 citations

Journal ArticleDOI
TL;DR: In this article , the authors proposed a new joining method for dissimilar materials which are particularly difficult to join by conventional fusion welding techniques, such as friction stir welding (FSW) and spot welding (FSSW).
Abstract: Abstract Numerous industrial applications, particularly those in the transport industry, require the joining of dissimilar materials which offers considerable benefits in terms of low cost, design flexibility, and weight reduction for overall structures. The problems associated with conventional fusion welding processes have stimulated researchers in recent years to develop new joining methods for dissimilar materials which are particularly difficult to join. Friction stir welding (FSW) originally developed for joining difficult-to-weld Al-alloys and FSSW (a variant of FSW for spot welding) have exhibited great potential for obtaining sound joints in various dissimilar alloy systems in different configurations namely butt-, lap- and spot-welding, particularly in dissimilar Al-alloys systems with different properties, which are very difficult to weld using conventional fusion welding techniques. A major difficulty in joining dissimilar Al-alloys by FSW/FSSW lies in the discontinuity in mechanical and technological properties (such as high-temperature strength, plastic deformation capacity, viscosity, etc.) of the materials to be welded across the abutting surfaces. This discontinuity as well as inherent asymmetry in heat generation and material flow of FWS/FSSW processes causes a higher asymmetry in materials flow behavior in dissimilar welding. However, it is relatively easier to implement the FSW/FSSW process to dissimilar Al-alloys in contrast to FSW of dissimilar materials combinations with very differing properties, such as Al-alloy to Mg-alloy or Al-alloy to steel.

43 citations

Journal ArticleDOI
TL;DR: In this paper, a multi-jet hydrodynamic approach was proposed to enhance the surface finish quality of the internal channels of a laser powder bed fusion (L-PBF) component.
Abstract: The surface roughness of components built using the laser powder bed fusion (L-PBF) process is poor. Surface finishing the internal channels of L-PBF components is a challenge. We propose a multi-jet hydrodynamic approach to enhance the surface finish quality of the internal channels. We investigate the hydrodynamic finishing on L-PBF Inconel 625 linear, stepped, and non-linear internal channels with diameters 5 to 1 mm and length up to 100 mm (replicating the geometries in rocket injectors, fuel nozzles, and cooling channels). The multi-jet hydrodynamic finishing approach improved the surface quality by 60–90 % (final Ra, Sa ≤ 1 μm and Rz, Sz ≤ 20 μm), using an abrasive concentration of ≤1 % in 15 min. of processing time. Areal surface texture parameters Sdr and roughness ratio r ≈1, evidenced the uniformity of the surface finish with dominant abrasive microcuts, regardless of the initial non-uniform additive manufactured surface. Most of the surface finished channels had excellent dimensional integrity and internal contour circularity. We then discussed the advancements required in metal additive manufacturing and internal surface finishing—to safely deploy L-PBF components with micro internal channels in fuel injection and fluid transfer applications.

42 citations

Journal ArticleDOI
TL;DR: In this paper , the authors summarize the recent progresses on the characterization of microstructure, assessment of strengthening and damage mechanisms, evaluation of fracture and fatigue resistance, and attempts to build a primary comprehensive link between mechanical performance and micro-structure for the as built state.
Abstract: As important structural materials widely used in aerospace and automotive industries, aluminum alloys are perfect candidates for development of laser metal additive manufacturing (AM). Amongst AM aluminum alloys, laser powder bed fusion (LPBF) AlSi10Mg has received substantial attention due to its good printability and relatively low cost. Great efforts have been devoted to seek optimum process parameters that can enhance mechanical performance. However, a large scattering of material properties arises from the literature data, especially for the as built state, thus casting a shadow over further development of LPBF Al alloys. This review article aims to summarize the recent progresses on the characterization of microstructure, assessment of strengthening and damage mechanisms, evaluation of fracture and fatigue resistance, and attempts to build a primary comprehensive link between mechanical performance and microstructure for the as built state. Following the analysis of the state of the art, the review will finally provide an outlook on additional efforts needed to quantify the microstructure-property relation, based on which maximizing the potential of mechanical performance through optimizing microstructure may be achieved.

34 citations