Browsing by Author "Ramalho, A."
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- Effect of artificial saliva on the fatigue and wear response of TiAl6V4 specimens produced by SLMPublication . Jesus, J. de; Borrego, L. P.; Vilhena, L.; Ferreira, J. A. M.; Ramalho, A.; Capela, C.Additive manufactured (AM) parts made in TiAl6V4 alloy are increasingly used in medical prostheses and dental implants, because of its high strength, low weight and excellent biocompatibility. These components work under environmentally assisted cyclic loading, i.e. under corrosion-fatigue, and/or subject to wear conditions. Fatigue performance of additive manufactured alloys is significantly influenced by the porosities, residual stresses, which can reduce its strength when compared with traditional materials. This paper presents the results of a fatigue crack propagation study in titanium TiAl6V4 specimens produced by selective laser melting (SLM) under artificial saliva ambient. Tests were performed using standard 6 mm thick compact specimens (CT) tested at R=0.05 and with frequencies of 1 and 10 Hz. The main objective of the current research work was studying the corrosion effect on the fatigue crack propagation of Selective Laser Melting (SLM) specimens, and to compare the tribocorrosion behaviour of two different specimens: one produced by SLM and the other by the conventional/traditional method. The study concluded that: AM Titanium Ti6Al4V alloy exhibits a moderate effect of saliva ambient on fatigue crack nucleation and on fatigue crack propagation, the wear rate coefficients for SLM and conventional manufactured specimens is of the same order, and the mechanism of abrasive wear is mainly with grooves aligned with the direction of sliding.
- Study of Laser Metal Deposition (LMD) as a Manufacturing Technique in Automotive IndustryPublication . Quaresma Ramalho, Francisco Miguel; Alves, M.L.; Correia, M. S.; Vilhena, L. M.; Ramalho, A.The last few decades in the automotive industry have been marked by a heavy concern with the environment, saving energy and reducing material wastage, while aiming to maintain good mechanical properties, essential in the components usage. Additive manufacturing (AM) techniques present themselves as a viable option in the matter, with Laser Metal Deposition (LMD), rising as one of the most promising techniques within this category, capable of producing near-net shape components, with a layer upon layer construction of three-dimensional solid parts from a 3D CAD model, with good mechanical properties and acceptable surface finishing. Laser Metal Deposition is a relatively recent technique, which is made noticeable by the lack of clarification about the influence of several parameters in the final components characteristics, ultimately leading to a scarce availability of the process in the market. This paper aims to clarify and evaluate, how LMD produced parts can suit the automotive industry, by measuring and analysing their behaviour under several mechanical tests. These mechanical tests have specific focus on wear and abrasion behaviour, as well as elastic properties determination, as these are the characteristics that allow a better overview over the expected performance of LMD components for automotive applications.