https://popups.uliege.be/esaform21/index.php?id=3570 Index terms fr 0 https://popups.uliege.be/esaform21/index.php?id=3714 Since its first synthesis in 2004 graphene was characterized intensively and exceptional properties in terms of e.g. mechanical strength, stiffness and electrical as well as thermal conductivity were revealed. These properties make graphene very attractive to be applied as additive in composite materials e.g. to increase strength and conductivity compared to the pure matrix material. In this study graphene nano platelets (GNP) in contents of 0. 5%, 1.0 % and 1.5 % were added to pure (99.7 %) aluminum powder and dispersed via EIRICH mixer method. This method is very appealing since homogenous mixtures can be achieved in significantly lower time when compared to e.g. the ball milling process. After subsequent cold compaction the composite materials were extruded with three different extrusion ratios. The influence of GNP content and extrusion ratio on the specific extrusion pressure is characterized as well the resulting rod surface quality, respectively. The effects of GNP content and extrusion ratio on homogeneity of graphene dispersion in the aluminum matrix, the relative density of the composite as well as hardness were also investigated. Mon, 29 Mar 2021 14:18:38 +0200 Fri, 14 May 2021 15:25:55 +0200 https://popups.uliege.be/esaform21/index.php?id=3714 https://popups.uliege.be/esaform21/index.php?id=3686 Liquid nitrogen cooling is widely used in the extrusion industrial practice in order to increase the production rate, to reduce the die temperature and to avoid defects on the profile exit surfaces resulting from an excessive heating. However, the efficiency of the cooling is deeply affected by position and design of the liquid nitrogen channel so that numerical modelling is gaining an increasing industrial interest in relation to the possibility offered to optimize the channel design without expensive and time-consuming experimental trials. In this work, a numerical FE model developed within COMSOL Multiphysics® is proposed and validated against experimental trials performed in industrial environment. The model combines the 3D simulation of the extrusion process with a 1D model of the cooling channel thus allowing the testing of a number of different solutions at the die design stage. The global aim of this work is the assessment of the liquid nitrogen cooling efficiency in the extrusion of an industrial aluminum profile and the proof of the potentials offered by numerical models to get an optimized channel design in terms of cooling efficiency, die thermal balancing and reduction of liquid nitrogen consumption. Mon, 29 Mar 2021 14:11:19 +0200 Mon, 26 Apr 2021 16:12:04 +0200 https://popups.uliege.be/esaform21/index.php?id=3686 https://popups.uliege.be/esaform21/index.php?id=3665 Tailored blanks, especially semi-finished parts formed by welding steel and aluminum alloys, are being employed in the automobile industry to reduce the weight of automobiles. However, when dissimilar metals are welded, galvanic corrosion due to differences in ionization tendency occurs, decreasing the reliability of such welded products. In addition, the heat input when aluminum alloys are welded causes an aging problem. In this study, combined-cycle corrosion testing was performed for S45C/6000 series steel/aluminum alloys joined by friction welding. First, S45C steel pipes were joined to A6061-T6 and A6063-T6 aluminum alloy pipes by friction welding. Then, after combined-cycle testing, changes in appearance and joint strength were investigated as the number of cycles increased. In the natural aging test, test pieces were placed in a desiccator whose temperature was adjusted to about 20 °C with a humidity from 0 to 10 %. One piece was removed at predetermined time intervals and used in tensile testing. After tensile testing, fracture surfaces were observed with an optical microscope. For the S45C/A6061 friction- welded material, a decrease in tensile strength was found at the 36th cycle. It was confirmed that the strength of the S45C/A6063 friction-welded material decreased clearly at the 27th cycle. Any obvious changes in strength were not seen in specimens after 540 hours of natural aging. Mon, 29 Mar 2021 14:00:28 +0200 Thu, 08 Apr 2021 19:09:43 +0200 https://popups.uliege.be/esaform21/index.php?id=3665 https://popups.uliege.be/esaform21/index.php?id=850 Electromagnetic forming is a contactless high-speed forming technique. In this process force transmission is initiated by an electromagnetic field provided by a tool coil. While forming thin sheet metal, the magnetic field is present in the whole depth of the sheet metal by definition. Thus, the magnetic field generates eddy currents in the complete sheet volume. The resulting Lorenz` forces act as body forces and are used for forming. Thereby high strain rates, high temperatures and multiaxial stress fields influence the plastic material properties of the workpiece. In this study, the plastic properties were investigated under real electromagnetic forming conditions. By varying process conditions like charge energy, sheet thickness and die material, the magnetic field and thus the plastic material properties were changed. To visualize the influence of the electromagnetic field, forming experiments were carried out. The strain of the formed sheets was measured. Furthermore, the forming forces were determined by measurements during the electromagnetic forming as well as by finite element simulations. With the measured strain and the determined forming force, a model for the plastic material behavior during electromagnetic forming was evolved. Sun, 21 Mar 2021 22:12:14 +0100 Fri, 02 Apr 2021 16:57:44 +0200 https://popups.uliege.be/esaform21/index.php?id=850 https://popups.uliege.be/esaform21/index.php?id=858 Composite materials are widely used as main parts and structural components in different fields, especially for automotive and military applications. Although these materials supply different advantages comparing to the metals, their implementation in engineering applications is limited due to low electrical and thermal properties and low resistance to erosion. To enhance these above-mentioned properties, the metallization of composite materials by creating a thin metal film on their surface can be achieved. Among different coating deposition techniques, Cold Spray appears to be the most suitable one for the metallization of temperature-sensitive materials such as polymers and composites with a thermoplastic matrix. This process relies on kinetic energy for the formation of the coating rather than on thermal energy and consequent erosion and degradation of the polymer-based composite can be avoided. In the last years, a new method to produce composite materials, as known as Fused Filament Fabrication (FFF), has been developed for industrial applications. This technique consists of a 3D printing process that involves the thermal extrusion of thermoplastic polymer and fibers in the form of filaments from a heated mobile nozzle. The implementation of this new technique is leading to the manufacturing of customized composite materials for the cold spray application. In the presented experimental campaign, Onyx material is used as a substrate. This material is made of Nylon, a thermoplastic matrix, and chopped carbon fibers randomly dispersed in it. Aluminum powders were cold sprayed on the Onyx substrate with a low-pressure cold spray (LPCS) system. This study aims to investigate the possibility of the metalizing 3D-printed composite material by cold spray technology. For this purpose, optical and microscopical analyses are carried out. Based on the results, the feasibility of the process and the influence of the morphology of the substrate are discussed, and optimal spraying conditions are proposed. Sun, 21 Mar 2021 22:20:35 +0100 Tue, 30 Mar 2021 11:03:16 +0200 https://popups.uliege.be/esaform21/index.php?id=858 https://popups.uliege.be/esaform21/index.php?id=2451 In this study, we focus on additive manufacturing using Laser Metal Deposition (LMD) to produce a large space aluminum component that is expensive to manufacture with conventional methods and requests a long lead time. Two main objectives are aimed at: the setup of the process with the determination of process parameters that lead to healthy parts and the demonstration that the component size and geometry is largely compatible with LMD. Two materials are considered for this component. AlSi10Mg and Scalmalloy®. Processing parameters have been optimized to obtain a density on both materials over 99.5%. The final material is chosen with regard to the mechanical performance. Scalmalloy provides both better strength and ductility and is chosen to print a demonstrator. The demonstrator printed in this study is a section of a large (1 m diameter) ring-shaped component that has been topologically optimized. Some modifications are made on the original design in order to make it compatible with LMD printing. The printing strategy is then established. The results of the (non-) destructive testing reveal that the demonstrator is healthy and the mechanical properties are as expected. Tue, 23 Mar 2021 19:11:35 +0100 Tue, 30 Mar 2021 09:03:22 +0200 https://popups.uliege.be/esaform21/index.php?id=2451