140 research outputs found
Processo di powder-based Additive Manufacturing per strutture ibride e su misura: uso della Direct Laser Deposition per nuove applicazioni nell'industria 4.0
No full textOptimization of Direct Laser Deposition Process for Hybrid and Tailored Structures
No full textAdditive Manufacturing represents one of the Key Enabling Technologies that allow the manufacturing industry to move forward to its highest evolved form thanks to its high design flexibility, the reduction of scrap materials, and the possibility to tailor the physical and mechanical properties of manufactured parts. More specifically, this work explores the feasibility of producing functionally graded parts by mixing two high-strength steels, i.e. AISI 316L and AISI H13, through Direct Laser Deposition (DLD). This Ph.D. thesis aims to generate new knowledge through an experimental approach that will enrich the landscape of DLD production of Functionally Graded Material (FGM) components. Two different research streams were simultaneously pursued: i) explore the potentialities of DLD in producing tailored parts with customized mechanical properties and chemical composition; ii) the formulation of reliable process guidelines. This work evaluated the optimization and manufacturing process starting from the feedstock analysis to the deposition of two kinds of functionally graded materials. The outcomes are discussed in a critical analysis with the objective of improving the engineered materials scenario for the die and mold industry applications. Finally, the validation of the optimized process parameters was achieved by the production of FGMs benchmarks, which are properly designed and characterized
Influence of Fibre Fill Pattern and Stacking Sequence on Open-Hole Tensile Behaviour in Additive Manufactured Fibre-Reinforced Composites
No full textAdditive manufacturing has revolutionised the field of manufacturing, allowing for the production of complex geometries with high precision and accuracy. One of the most promising applications of additive manufacturing is in the production of composites, which are materials made by combining two or more substances with different properties to achieve specific functional characteristics. In recent years, the use of Continuous Filament Fabrication (CFF) in additive manufacturing has become increasingly popular due to its ability to produce high-quality composite parts which have fibres with a complex orientation and high curvature. This paper aims to investigate the influence of fill pattern and stacking sequence on the open-hole tensile strength of composites manufactured using CFF and made of an innovative matrix composed of nylon and short carbon fibres, i.e., Onyx, and with continuous carbon fibre as reinforcement. By systematically varying the fill pattern and stacking sequence, we aim to identify the optimal combination that can achieve the highest open-hole tensile strength in these composites. The results of this study will provide valuable insights into the design and manufacture of high-strength composites using additive manufacturing. Open-hole strength and elastic properties are strongly influenced by the infill strategy and stacking sequences adopted, and show different failure modes. The results also point out a technological issue characterising the process and indicate some guidelines for designing and manufacturing 3D printing composites
Pin-bearing mechanical behaviour of continuous reinforced Kevlar fibre composite fabricated via fused filament fabrication
No full textIn this study, the pin bearing behaviour of a 3D printed composite material with Kevlar reinforcement was analysed. Three different experimental tests were designed to determine the effects of fibre orientation, layer design, and fibre distribution along the specimen thickness. Furthermore, the pin-bearing strength and stiffness were analysed using statistical methods as analysis of variance. The results indicate a significant increase in bearing strength and stiffness for at least two fibre orientations, i.e. 0°and 90° with respect to the pin displacement. The results also highlight a no significant variation of strength and stiffness for parts produced adopting a mixed or single fibre orientation; finally, the findings do not indicate any significant influence of the fibre layer position inside the specimen, i.e. this parameter does not limit the freedom when designing a fibre-reinforced part
Pin-bearing mechanical behaviour of composites fabricated via fused filament fabrication as a function of reinforcing, pin diameter and W/D ratio
No full textAdditive manufacturing is an advanced technology able to produce parts with different grades of complexity, including its shape, microstructure, functionality and material. Regarding material complexity nowadays, it is possible to produce polymer parts with customized reinforced fibre filling such as carbon, Kevlar or glass. However, their mechanical behaviour is still under investigation and no data are available on the bearing strength for additively manufactured composites. The aim of this work is to provide a contribution on this topic to ensure safe joint design with the current and innovative technologies. In this article the authors present the experimental characterization of polymer filled with Kevlar to pin bearing test. Samples have been designed as a function of filling and geometry parameters. Results have been analysed with statistical methods. Finding highlight similar and different behaviour regarding samples produced with conventional process. The most interesting result is that the authors demonstrate how the pin diameter is significant for the results, particularly for the stiffness keeping constant the bearing strength
Influence of Fibre Fill Pattern and Stacking Sequence on Open-Hole Tensile Behaviour in Additive Manufactured Fibre-Reinforced Composites
No full textAdditive manufacturing has revolutionised the field of manufacturing, allowing for the production of complex geometries with high precision and accuracy. One of the most promising applications of additive manufacturing is in the production of composites, which are materials made by combining two or more substances with different properties to achieve specific functional characteristics. In recent years, the use of Continuous Filament Fabrication (CFF) in additive manufacturing has become increasingly popular due to its ability to produce high-quality composite parts which have fibres with a complex orientation and high curvature. This paper aims to investigate the influence of fill pattern and stacking sequence on the open-hole tensile strength of composites manufactured using CFF and made of an innovative matrix composed of nylon and short carbon fibres, i.e., Onyx, and with continuous carbon fibre as reinforcement. By systematically varying the fill pattern and stacking sequence, we aim to identify the optimal combination that can achieve the highest open-hole tensile strength in these composites. The results of this study will provide valuable insights into the design and manufacture of high-strength composites using additive manufacturing. Open-hole strength and elastic properties are strongly influenced by the infill strategy and stacking sequences adopted, and show different failure modes. The results also point out a technological issue characterising the process and indicate some guidelines for designing and manufacturing 3D printing composites
Dissimilar friction stir lap welding of AA2198-AA6082: Process analysis and joint characterization
No full textThis paper deals with the dissimilar friction stir lap welding of AA2198 and AA6082 thin sheets. The influence of processing parameters, namely welding speed and tool rotational speed on joint features, microstructure, and mechanical properties were investigated by implementing a full factorial design of experiments. During the welding process, axial and transversal forces were continuously measured using a dedicated fixture equipped with sensors aiming at the correlation of this processing parameter with the quality of the achieved joints. The microstructural analysis provided a detailed view of the metallurgical features such as hook, and its relative influence exhibited on the welded joints. Microhardness distribution and lap shear behavior were assessed and correlated with the metallurgical analysis
Fluidized bed finishing of additively manufactured objects: The influence of operating parameters
No full textThis study investigates the potential of Fluidized Bed Finishing (FBF) of square flat AlSi10Mg specimens manufactured via Laser-Powder Bed Fusion (L-PBF) additive manufacturing technology. Two FBF operational modes were experimentally investigated: I) with stationary specimens; II) with specimens under controlled rotational motion. Four different abrasive materials have been tested, quartz sand, corundum, irregular steel and cut wire steel particles, characterized by different hardness, density and shape. The effect of the abrasive material, processing time and specimen tilt angle was investigated. Results showed moderate smoothing under stationary specimen configuration, while good finishing for rotation-assisted tests, maximum reduction of the surface roughness of 12% and 67%, respectively. Steel particles were the most effective bed material, with particle density overtaking hardness as key particle property. The optimal tilt angle was the one that maximized sliding and shear. Altogether, surface finishing is driven by surface shear forces dominated by inertial stresses in particulate phase
Electron beam melting of Ti6Al4V: Role of the process parameters under the same energy density
No full textThe role of the process parameters under a fixed energy density in Electron Beam Melting of Ti6Al4V was investigated. The beam current, scan speed and line offset were varied in a wide range keeping constant the energy density achieved, aiming to highlight the influence of each parameter on the properties of the printed parts. Microstructure, microhardness and top surface roughness were chosen as measured output. The results obtained showed that the amount of energy adsorbed by the metal is depending on beam current and scan speed, this due to the complex interaction between the electrons of the beam and the atoms of the material. As a consequence, the samples showed different properties, even if the adopted energy density was the same, the influence of the process parameters on the above-mentioned measured output was assessed
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