1,721,031 research outputs found
Simulation of laser-assisted directed energy deposition of aluminum powder: Prediction of geometry and temperature evolution
No full textOne of the main current challenges in the field of additive manufacturing and directed energy deposition of metals, is the need for simulation tools to prevent or reduce the need to adopt a trial-and-error approach to find the optimum processing conditions. A valuable help is offered by numerical simulation, although setting-up and validating a reliable model is challenging, due to many issues related to the laser source, the interaction with the feeding metal, the evolution of the material properties and the boundary conditions. Indeed, many attempts have been reported in the literature, although some issues are usually simplified or neglected. Therefore, this paper is aimed at building a comprehensive numerical model for the process of laser-assisted deposition. Namely: the geometry of the deposited metal is investigated in advance and the most effective reference shape is found to feed the simulation as a function of the governing factors for single- and multi-track, multi-layer deposition; then, a non-stationary thermal model is proposed and the underlying hypotheses to simulate the addition of metal are discussed step-by-step. Validation is eventually conducted, based on experimental evidence. Aluminum alloy 2024 is chosen as feeding metal and substrate
Optimization of laser beam welding of steel parts made by additive manufacturing
No full textTo pursue all the benefits of additive manufacturing of metals, recent studies have been aimed at assessing a proper welding technology to obtain large products by means of joining smaller parts. Indeed, at present, two or more parts must be manufactured individually and then assembled to produce the final component, when the size is incompatible with the building chamber or severe deformations arise during building. In this paper, laser beam welding is explored to join stainless steel components made by the process of laser powder bed fusion, in order to benefit from all the known advantages of this joining technique, aiming at producing a welding bead with homogeneous mechanical features with respect to the unwelded counterpart: a factorial plan is built, and the response surfaces are presented; then, the consolidated method of the desirability function is used to find the optimum condition of welding with reference to the current international standards, taking into account the geometry, the welding imperfections, and the extent of the heat-affected zone. The suggested optimum is eventually assessed via tensile testing and compared to the unwelded sample
Fisiologia, morale e demonologia. Il corpo conteso di fra Giovanni Battista (Terra d'Otranto, 1688)
No full textIl saggio esplora la vicenda emersa da un processo inquisitoriale della seconda metà del XVII secolo, contro un cappuccino sospetto di quietismo. Fra credenze pseudoscientifiche e superstizioni, procedure giuridiche e argomentazioni teologiche, il processo costituisce una finestra di eccezione sulla mentalità diffusa in ambito cattolico sul corpo maschile, in particolare sul corpo del clero consacrato alla castità
Additive Manufacturing in aeronautics: An overview and a case-study
No full textAdditive Manufacturing is receiving growing interest in the aeronautics thanks to massive improvements in terms of equipment and materials and increasing availability of specific standards. Among the processes, technologies for metals have been suggested for functional parts, whereas those for non-metal are generally preferred for non-critical component. Therefore, the paper focuses on the processes of laser-based powder bed fusion and directed energy deposition, the latter having been already considered for many applications in the field of interest. Nevertheless, some issues must be addressed and are presented, referring to a case-study of cladding over an aluminium plate, with preliminary numerical simulation and eventual treating by means of laser surface modification to reduce the final roughness
Alfieri (V. E.), Gli atomisti. Frammenti e testimonianze. Traduzione e note
No full textDelatte A. Alfieri (V. E.), Gli atomisti. Frammenti e testimonianze. Traduzione e note. In: Revue belge de philologie et d'histoire, tome 15, fasc. 3-4, 1936. pp. 1008-1009
Alfieri (V. E.), Gli atomisti. Frammenti e testimonianze. Traduzione e note
No full textDelatte A. Alfieri (V. E.), Gli atomisti. Frammenti e testimonianze. Traduzione e note. In: Revue belge de philologie et d'histoire, tome 15, fasc. 3-4, 1936. pp. 1008-1009
Directed Energy Deposition of stainless steel wire with laser beam: Evaluation of geometry and affection depth
No full textThis paper is aimed at investigating the process of Directed Energy Deposition of steel wire to the purpose of maintenance and repair: this technology is receiving increasing interest in the frame of Additive Manufacturing and has been investigated for different metals and different substrates. An experimental plan has been designed here to investigate the dependence of the geometry on the governing factors in single-track deposition and quantify the depth of the affection in the substrate in terms of geometrical dilution and variation of the micro-hardness
Design of a neural virtual sensor for the air and charging system in a Diesel engine
Full text linkThe main objective of this work is to design a virtual sensor capable of estimating variables that are unmeasurable on-line in the air and charging subsystem of a Diesel engine. In order to achieve this objective, a data-driven approach is pursued. In particular, we show that combining high-gain observers and feed-forward neural networks, it is possible to design an observer for the air and charging system of a Diesel engine on the basis of data acquired via a test bench. The performance of this observer is evaluated in a real experimental setting
On the Relevance of volumetric energy density in the investigation of inconel 718 laser powder bed fusion
No full textLaser powder bed fusion (LPBF) can fabricate products with tailored mechanical and surface properties. In fact, surface texture, roughness, pore size, the resulting fractional density, and microhardness highly depend on the processing conditions, which are very difficult to deal with. Therefore, this paper aims at investigating the relevance of the volumetric energy density (VED) that is a concise index of some governing factors with a potential operational use. This paper proves the fact that the observed experimental variation in the surface roughness, number and size of pores, the fractional density, and Vickers hardness can be explained in terms of VED that can help the investigator in dealing with several process parameters at once
Additive manufacturing of biomorphic scaffolds for bone tissue engineering
No full textBone tissue engineering has evolved owing to new opportunities of deep customisation offered by additive manufacturing technologies. Gyroid structures, which have been widely used for energy absorption or chemical catalysis, are now being employed as biomorphic structures as well to provide customer-oriented scaffolds for missing or injured bones. Unfortunately, limited data in terms of manufacturability and mechanical properties are available in the literature to support a wide application scope, because the bone to match is strongly dependent on the individual. Therefore, the study aimed at addressing this lack of knowledge, assessing the manufacturability of metal gyroids and further developing the correlation of the structural response with the designed geometry, so to allow the designer to provide the proper biomorphic structure on a case-by-case basis. Biocompatible steel was used to manufacture samples via laser powder-bed fusion; their elastic moduli and yield strengths were evaluated as a function of the orientation of the elementary cells, the symmetry and the wall thickness based on compression testing. Grounds have been given to support potential applications for tibias and vertebras
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