Browsing by Author "Jesus, J. S."
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- Fatigue crack growth behaviour in Ti6Al4V alloy specimens produced by selective laser meltingPublication . Jesus, J. S.; Borrego, L. P.; Ferreira, J. A. M.; Costa, J. D.; Capela, C.The current study presents the fatigue crack growth behaviour of titanium alloy Ti6Al4V parts manufactured by selective laser melting (SLM), obtained as standard 6 mm thick compact specimens (CT). Both the crack propagation under constant amplitude loading and the transient crack growth behaviour after the application of overloads were studied. The effect of the mean stress and the transient retardation behaviour were analysed using the crack closure parameter, obtained both by compliance and digital image correlation techniques. A reduced crack closure level for the stress ratio R = 0 was detected and for R = 0.4 no crack closure was observed. The digital image correlation technique showed better results in the Paris regime and during the transient retardation behaviour. The overload application produced crack growth retardation due to the increase of the crack closure effect. The failure surfaces showed a transgranular crack growth in β phase contouring the martensitic α phase.
- Fatigue crack growth under corrosive environments of Ti-6Al-4V specimens produced by SLMPublication . Jesus, J. S.; Borrego, L. P.; Ferreira, J. A. M.; Costa, J. D.; Capela, CarlosAdditive manufactured parts made of Ti-6Al-4V alloy are increasingly used in medical devices and in the aeronautical industry, because of its high strength, low weight and excellent biocompatibility. Most of these components work under environmentally assisted cyclic loading, i.e. under corrosion-fatigue. Anisotropic microstructure of additive manufactured materials significantly influences the propagation of cracks, particularly under corrosion-fatigue. This paper presents the results of the failure mode and fatigue crack propagation study in titanium Ti-6Al-4V specimens produced by selective laser melting (SLM), under corrosive ambient. Three environment solutions were used: artificial saliva, Ringer's solution and 3.5%wt NaCl solution. Tests were performed using standard 6 mm thick compact specimens (CT) tested at R = 0.05 with frequencies of 1 and 10 Hz. The main objective was to study the effect of the corrosion potential on da/dN-ΔK curves and on the fatigue failure mechanisms. It was observed a very important accelerating effect on the crack initiation and fatigue crack propagation for tests under corrosion ambient, particularly for 3.5%wt NaCl solution, for which fatigue crack growth is 3.3 times higher in comparison with inert ambient tests.