14 documents found, page 1 of 2
Development of a gas metal arc based prototype for direct energy deposition wit...
Dornelas, Paulo Henrique Grossi; Oliveira, J. P.; Silva, Tadeu Castro da; Ramos, Ana Sofia; Santos, Telmo G.In recent years, efforts have been focused on the development of metal additive manufacturing (AM) processes to address the growing trend of miniaturization in industries such as aerospace and electronics. Thus, new technologies have been developed based on a downscaled approach using direct energy deposition (DED) processes, now referred to as μ-DED. In this context, the development of a downscaled DED prototy...
Joining of Ti6Al4V to Al2O3 Using Nanomultilayers
Silva Jr., Marcionilo; Ramos, Ana Sofia; Vieira, Maria Teresa; Simões, SóniaDiffusion bonding of Ti6Al4V to Al2O3 using Ni/Ti reactive nanomultilayers as interlayer material was investigated. For this purpose, Ni/Ti multilayer thin films with 12, 25, and 60 nm modulation periods (bilayer thickness) were deposited by d.c. magnetron sputtering onto the base materials’ surface. The joints were processed at 750 and 800 ◦C with a dwell time of 60 min and under a pressure of 5 MPa. Microstru...
Development of Actuators for Repairing Cracks by Coating W Wires with Reactive ...
Silva, Gabriel Santos; Maj, Lukasz; Morgiel, Jerzy; Vieira, Maria Teresa; Ramos, Ana SofiaThe aim of this research work was to optimize the coating of tungsten wires with reactive multilayer thin films and promote an exothermic self-propagating reaction. The ultimate goal is to use this heat to liquify low melting temperature materials, and thus block crack propagation in metallic materials. Ni/Me (Me = Al, Ti) multilayers were deposited by a DC (direct current) magnetron sputtering onto tungsten wi...
Searching new solutions for NiTi sensors through indirect additive manufacturing
Carreira, Pedro; Gatões, Daniel; Alves, Nuno; Ramos, Ana Sofia; Vieira, Maria TeresaShape Memory Alloys (SMAs) can play an essential role in developing novel active sensors for self-healing, including aeronautical systems. However, the NiTi SMAs available in the market are almost limited to wires, small sheets, and coatings. This restriction is mainly due to the difficulty in processing NiTi through conventional processes. Thus, the objective of this study is to evaluate the potential of one o...
Experimental Analysis of NiTi Alloy during Strain-Controlled Low-Cycle Fatigue
Lima, Pedro Cunha; Rodrigues, Patrícia Freitas; Ramos, Ana Sofia; Costa, José D. M. da; Braz Fernandes, Francisco Manuel; Vieira, Maria TeresaThe interaction between the stress-induced martensitic transformation and resistivity behavior of superelastic NiTi shape memory alloy (SMA) was studied. Strain-controlled low-cycle fatigue up to 6% was monitored by in situ electrical resistivity measurements. The experimental results show that a great motion of martensite fronts results in a significant accumulation of defects, as evidenced by transmission ele...
Investigating a Commercial Functional Adhesive with 12-MDPB and Reactive Filler...
Belmar da Costa, Madalena; Delgado, António H. S.; Amorim Afonso, Tomás; Proença, Luís; Ramos, Ana Sofia; Mano Azul, AnaTo compare the adhesive interface of eroded dentin formed by a functional dental adhesive and a gold standard strategy, by testing microtensile bond strength ( TBS), hardness/elastic modulus. Permanent sound human molars were randomly allocated to four experimental groups, all subject to artificial erosion (0.05 M citric acid; 3 daily, 5 days). Groups included control Clearfil SE Bond 2 (CFSE), and experimental...
Investigating a commercial functional adhesive with 12-MDPB and reactive filler...
Costa, Madalena Belmar da; Delgado, António H. S.; Afonso, Tomás Amorim; Proença, Luís; Ramos, Ana Sofia; Azul, Ana ManoTo compare the adhesive interface of eroded dentin formed by a functional dental adhesive and a gold standard strategy, by testing microtensile bond strength (μTBS), hardness/elastic modulus. Permanent sound human molars were randomly allocated to four experimental groups, all subject to artificial erosion (0.05 M citric acid; 3× daily, 5 days). Groups included control Clearfil SE Bond 2 (CFSE), and experimenta...
Effect of Deposition Parameters on the Reactivity of Al/Ni Multilayer Thin Films
Ramos, Ana Sofia; Simões, Sónia; Maj, Lukasz; Morgiel, Jerzy; Vieira, Maria TeresaNanoscale multilayers can be used as highly localized heat sources, making them attractive for several applications, in particular for joining and as igniters. Over the last decades, academia and industry have given particular emphasis to nanoscale multilayers from the Ni–Al system. In this study, Al/Ni (V) multilayer thin films with periods of nominally 25 and 50 nm (bilayer thickness) and near equiatomic aver...
Interaction between Ni/Ti Nanomultilayers and Bulk Ti-6Al-4V during Heat Treatment
Cavaleiro, André João; Ramos, Ana Sofia; Fernandes, Francisco; Baehtz, Carsten; Vieira, Maria TeresaThe diffusion bonding of Ti-6Al-4V to NiTi alloys assisted by Ni/Ti reactive multilayer thin films indicates the diffusion of Ni from the filler material towards bulk Ti-6Al-4V. As a consequence, the fragile NiTi2 intermetallic phase is formed at the joint interface. In this context, the aim of this work is to investigate the occurrence of Ni diffusion from Ni/Ti nanomultilayers towards Ti-6Al-4V substrates. Fo...
Intermetallics
Ramos, Ana SofiaThe combination of low density, high strength, and good corrosion resistance makes intermetallics promising for structural applications, especially at high temperatures and under severe environments [1]. These materials have also potential for functional applications since some intermetallic phases have unique properties, such as shape memory or thermo electric effect. Intermetallic phases of interest include a...