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Percorrer ESAD.CR - Artigos em revistas internacionais por Objetivos de Desenvolvimento Sustentável (ODS) "12:Produção e Consumo Sustentáveis"
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- Aluminum-to-Steel Cladding by Explosive WeldingPublication . Carvalho, Gustavo H. S. F. L.; Galvão, Ivan; Mendes, Ricardo; Leal, Rui M.; Loureiro, AltinoThe production of aluminum-carbon steel and aluminum-stainless steel clads is challenging, and explosive welding is one of the most suitable processes to achieve them. The present work aims to investigate the coupled effect of two strategies for optimizing the production of these clads by explosive welding: the use of a low-density interlayer and the use of a low-density and low-detonation velocity explosive mixture. A broad range of techniques was used to characterize the microstructural and the mechanical properties of the welds, specifically, optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, electron backscatter diffraction, microhardness and tensile-shear testing with digital image correlation analysis. Although aluminum-carbon steel and aluminum-stainless steel have different weldabilities, clads with sound microstructure and good mechanical behavior were achieved for both combinations. These results were associated with the low values of collision point and impact velocities provided by the tested explosive mixture, which made the weldability difference between these combinations less significant. The successful testing of this explosive mixture indicates that it is suitable to be used for welding very thin flyers and/or dissimilar materials that easily form intermetallic phases.
- Explosive welding of aluminium to stainless steel using carbon steel and niobium interlayersPublication . Carvalho, G.H.S.F.L.; Galvão, I.; Mendes, R.; Leal, R. M.; Loureiro, A.This work aimed to study aluminium to stainless steel explosive welds produced using two different interlayers: carbon steel and niobium. The use of each interlayer was analysed and compared microstructurally and mechanically using many characterisation techniques. The final joints using both interlayers presented favourable interfacial microstructure: waves on both interfaces. However, the joint using the carbon steel interlayer showed the best mechanical properties compared to the joints using the niobium interlayer. All interfaces found on both welds were wavy. However, depending on the metallic alloy combination, the shape of the wave is completely different. The results suggest that the shape of the waves is influenced by the shock impedance mismatch of the materials being welded. The impedance mismatch parameter (IMP) developed for explosive welding in this work proved to be a compelling method to order metallic combinations in a single axis to estimate the tendency to form typical or curled waves. Typical symmetrical waves tend to develop less quantity of IMCs than curled waves. However, the mechanical tests performed did not detect differences that could have been caused by this difference.
- The Fourth “R” - The Reversion of Objects as a Way of Reducing WastePublication . S. GonçalvesGiven the evident inefficiency of the policies and mechanisms established to deal with environmental degradation, it is essential to understand the reasons for their failures and to try alternative ways to mitigate the environmental problems associated with the replacement of objects. The ideas behind the so-called “3 R’s” policy, born of a sequence of two defining moments in the definition of environmental policies in Europe, - Agenda XXI in 1992 [1] and the 5th European Environment and Development Program of 1993 - have produced encouraging results since their creation, but failed to halt the increasing degradation of the environment on a planetary level. One of the problems derives from the fact that any of r's is strongly dependent on the environmental conscience, or even ethics, of the citizens responsible for the decisions regarding the products in their different moments of existence - from their design and production to their use and subsequent destination. This dependence leads to a high fallibility of environmental policies, insofar as western society suggests, in the way it behaves, a direction opposite to that which they advocate. It is thus important to reflect on ways of designing and producing things whose environmental performance is less dependent on the environmental consciousness of the end user, so that this awareness is not so decisive in the impact resulting from the disposal of objects. The present work tries to analyse the response of a group of students of design to the introduction of a “4thR”, that we call Reversion, and that is to think products of daily use whose form is conditioned by the necessity of its components can be, when dismantled of the system, seen as raw material directly usable for another purpose, easily determined by the user, and not as a technical component of an obsolete system. Functional prototypes will be realized in order to evaluate and validate the products regarding their effective performance in terms of production and use, as well as the possibility of reuse of their components in contexts other than those for which the objects were designed.
- Influence of Tool Geometry and Process Parameters on Torque, Temperature, and Quality of Friction Stir Welds in Dissimilar Al AlloysPublication . Manuel, Neves; Beltrão, Daniel; Galvão, Ivan; Leal, Rui M.; Costa, José D.; Loureiro, AltinoIn the current investigation, the influence of the tool geometry, the position of the materials in the joint, the welding speed on the temperature and torque developed, and on the quality of the welds in dissimilar and tri-dissimilar T joints were analysed. The aluminium alloys used were AA2017-T4, AA6082-T6, and AA5083-H111 and the friction stir welds were performed with identical shoulder tools, but with either a pin with simple geometry or a pin with progressive geometry. Progressive pin tools proved to be a viable alternative in the production of dissimilar and tri-dissimilar welds, as they provide a larger tool/material friction area and a larger volume of dragged material, which promotes an increase in the heat generated and a good mixing of the materials in the stir zone, although they require a higher torque. Placing a stronger material on the advancing side also results in a higher temperature in the stir zone but requires higher torque too. The combination of these factors showed that tools with a progressive pin provide sound dissimilar and tri-dissimilar welds, unlike single-pin tools. The increase in the welding speed causes the formation of defects in the stir zone, even in tri-dissimilar welds carried out with a tool with a progressive pin, which impairs the fatigue strength of the welds.