1,721,003 research outputs found
Numerical investigations on the rebound phenomena and the bonding mechanisms in cold spray processes
No full textCold spray technology is a relatively new additive process allowing to create high quality metallic coatings, on both metallic and non-metallic substrates, without extensive heating of the powders sprayed. Upon impact with a target surface, conversion of kinetic energy to plastic deformation occurs, the solid particles deform and bond together. The actual bonding mechanism for cold spray particles is still not well understood, a high number of works has been carried out during the past two decades, several theories have been proposed to explain the adhesion/rebound mechanisms making the system ineffective for industrial applications. Therefore, the aim of this research activity is to better explain the complex adhesion/rebound phenomena into cold spray impact processes through numerical simulations; for this purpose, on the base of simplified hypothesis and results found in literature, an original 3D Finite Element Method (FEM) model of an aluminium particle impacting on an aluminium substrate was proposed. A cohesive behaviour algorithm was implemented in the particle-substrate contact regions aiming to simulate the bonding between the impacting particle and the substrate under specific working conditions. A rebound coefficient was also defined representing the particle residual energy. Different simulations were performed using a range of impact velocities and varying the interfacial cohesive strength. It was shown that at low impact velocities the rebound phenomenon is governed by the elastic energy stored in the system, meanwhile at high impact velocities, the rebound phenomenon is mainly due to the strain rate effects making the system mechanically stronger; therefore, a specific range of bonding velocities depending on substrate-particle contact area were found
A Preliminary Study on the Sustainability of Metallization of Polymer Matrix Composites through Cold Spray
Full text linkCold spraying of tailored aluminium foam precursors: Investigating the correlation between spraying conditions and foam morphology
Full text linkAn Experimental–Numerical Analysis of Innovative Aluminum Foam-Based Sandwich Constructions Under Compression Loads
No full textRecent studies have highlighted the effectiveness of using closed-cells aluminum foams as core of sandwich constructions, making them attractive for industrial applications. In previous studies, the authors proved the possibility of developing innovative sandwiches by using aluminum foams as core and stainless-steel grid as reinforcing skin, through a one-single foaming step and without using any molds. In line with this topic, the present work investigates the possibility of improving the compression strength of these constructions by integrating the same grid, used as skin, inside the core as corrugated skeleton. For this purpose, sandwiches with different geometries were manufactured and characterized mechanically. An original numerical FEM model was developed in support of the experimental campaign to thoroughly investigate the foam/grid interaction, as well as the failure mechanisms, in order to study the effects of the skeleton shape on the compression behavior of the sandwiches
Integrating 3D printing of polymer matrix composites and metal additive layer manufacturing: surface metallization of 3D printed composite panels through cold spray deposition of aluminium particles
Full text linkThe integration of metals and polymers in the same component to couple the best properties and advantages of both these classes of materials can be useful for engineering applications. In this scenario, the aim of this paper is to integrate additive manufacturing of composites with cold spray deposition of metal particles: in particular, 3D-printed carbon fibre-reinforced plastics (CFRP) panels were coated with aluminium particles to couple the lightweight and high mechanical properties of CFRP with high wear resistance and hardness of metals. CFRP panels have been produced by using the Fused Filament Fabrication (FFF) technology, then the panels have been coated with aluminium particles by using a low pressure cold spray facility. Panels with various stratification sequences have been produced to investigate the feasibility of the process and to highlight the influence of the lay-up strategy on the whole process; the parameters of the cold spray process have been also optimized to ensure an effective deposition. Adhesion tests, distortion measurements, cross-section observations and surface coverage measurements have been chosen as response outputs to evaluate the effectiveness of the process and to assess the influence of the process parameters. The integration between FFF of CFRPs and cold spray deposition of aluminium particles has been proved, values of surface coverage close to 100% and good values of adhesion strength (close to 4 MPa) have been achieved; moreover, the presence of the fibres, giving a higher stiffness to the substrate, avoids the occurrence of distortion phenomena during the deposition. It was also proved that the printing parameters influence the deposition: an increase in the infill density from 30% to 50% leads to an increase in the adhesion strength up to 40%. In summary, the results obtained proved the feasibility of the process and allowed to enucleate directions of future research
On the influence of different superficial laser texturing on the deposition of powders through cold spray process
No full textCold spray is a technique allowing the deposition of metallic powders on several different substrates. The deposition process is ruled by different factors, among these, of particular interest are the superficial roughness and texturing of the substrate. The aim of this research was to study the influence of different superficial texturing on the deposition process of aluminium powders on an AA 2024 T3 plate. Samples with different superficial texturing were produced by laser engraving through a Yb:YAG fibre laser, varying the laser treatment parameters. Aiming to highlight the influence of the laser treatment, the deposition process was carried out on all the samples under the same spraying condition. The cross-section of the interface between the substrate and the coating and the microstructure of the coating itself were observed to study the influence of the superficial texturing on the coating formation. It was found that the superficial texturing influences both the adhesion mechanism and the microstructure of the coating
An Innovative Manufacturing Method of Aluminum Foam Sandwiches using a Mesh-Grid Reinforcement as Mold
No full textAluminum foams are becoming potential materials for applications in several industrial fields, due to an intriguing combination of physical and mechanical properties. Their performances can be enhanced by using them as core of reinforced systems, like sandwich structures. Traditional reinforced foams usually present metal sheets or composite materials as skins, but these solutions are in contrast with some requirements of industrial applications, like lightness and high-temperature resistance. This work proposes an innovative single-step process, based on the powder compact melting technique, for the manufacture of aluminum foam panels reinforced by a steel wire mesh-grid, also acting as a mold. In doing so, problems of cost-effectiveness and flexibility typical of the conventional in-mold processes can be overcome on one hand and light-weight, high-temperature resistant aluminum foam sandwiches can be made on the other. A manufacturing campaign yielded the optimal foaming temperature for the production of the sandwich panels. In addition, mechanical tests highlighted the effectiveness of the mechanical coupling between the core and skin and a significant improvement of the bending load carrying capacity, compared to plain foam panels, of these innovative sandwiches
An experimental/numerical study of bonding mechanism in cold spray technology for metals
No full textThe cold spray technology is a relatively new additive process allowing for the deposition of metallic coatings on metallic substrates; the particles impacting on target surface at high velocity deform and bond together leading to the coating formation and grow-up. Although the impact phenomena have been studied by several scientists in the last decades, the actual bonding mechanism for cold spray particles is still a recent focus of research. Therefore, aiming to further investigate the intriguing phenomena governing the particle-substrate interaction in cold spray, both experimental and numerical studies were carried out in this research activity. Ballistic tests were performed by impacting a single lead particle (1.5 mm in diameter) on a lead substrate at different impact velocities through a light ballistic airgun. A high-frequency camera was used to observe the particle impact and measure impact and rebound velocities. A detailed 3D quarter symmetric numerical model was developed and impact simulations were performed. The comparison between the experimental results and the numerical outcomes in terms of particles and substrate deformations as well as particle rebound velocity allowed for the validation of the model. The validated numerical approach was used to study the thermo-mechanical regimes taking place on impact surface pointing out the rule of strain-temperature interaction in cold spray bonding. On these results, a temperature-based bonding hypothesis was proposed and an original bonding algorithm was implemented on the numerical model
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