Encontrados 21 documentos, a visualizar página 1 de 3
Factors affecting the metal recovery yield during induction melting of aluminiu...
Puga, Hélder; Barbosa, J.; Ribeiro, Carlos SilvaMachining operations of cast parts usually generate considerable amounts of waste in the form of chips (usually 3–5% of the casting weight). Traditionally, swarf is sold to scrapers and remelters, but this option is quite expensive because the selling price is roughly 30% of the acquisition price of the commercial 2nd melt raw material. For most aluminium foundries that incorporate machining operations in their...
Aluminium evaporation during ceramic crucible induction melting of titanium alu...
Gomes, Fernando Manuel Duarte; Barbosa, J.; Ribeiro, Carlos SilvaMelting TiAl based alloys in ceramic crucibles often leads to chemical contamination, alloy heterogeneity and non-metallic inclusions. The severity of such phenomena usually depends on the nature of crucible materials, the melting stock composition and the melting parameters, namely superheating time and temperature and melting pressure. Among the referred drawbacks, Al loss during melting is a critical aspect,...
Evaluation of functionally graded ceramic crucible for induction melting of TiA...
Gomes, Fernando Manuel Duarte; Barbosa, J.; Ribeiro, Carlos SilvaDuring the last years a very significant effort to develop a melting crucible for induction melting of Ti based alloys at competitive cost has been carried out by many researchers, where the authors are included. Results obtained so far have shown that no material accomplishes the melting crucibles two main demands: inertness facing titanium alloys and suitable/enough thermal-shock resistance. Until now, yttriu...
Influence of indirect ultrasonic vibration on the microstructure and mechanical...
Puga, Hélder; Barbosa, J.; Costa, Sónia; Ribeiro, Carlos Silva; Pinto, A. M. P.; Prokic, MiodragThe influence of high intensity ultrasound (US) propagating through a steel mold on the microstructure and mechanical properties of die-cast AlSi9Cu3, for different levels of electric power and at different distances to the waveguide/mold interface. The influence of those parameters on the morphology of -Al and eutectic Si and on the volume of porosity were investigated and characterized. The morphological ch...
Use of acoustic energy in the processing of molten aluminium alloys
Puga, Hélder; Barbosa, J.; Costa, Sónia; Ribeiro, Carlos SilvaDuring the last years aluminium alloys have been gaining increased acceptance as structural materials in the automotive and aeronautical industries, mainly due to their light weight, good formability and corrosion resistance. However, improvement of mechanical properties is a constant in research activities, either by the development of new alloys or by microstructure manipulation. This presentation focuses a ...
An iterative pilot-data-aided estimator for SFBC relay-assisted OFDM-based systems
Neves, Darlene; Ribeiro, Carlos; Silva, Adão; Gameiro, AtílioIn this article, we propose and assess an iterative pilot-data-aided channel estimation scheme for space frequency block coding relay-assisted OFDM-based systems. The relay node (RN) employs the equalise-and-forward protocol, and both the base station (BS) and the RN are equipped with antenna arrays, whereas the user terminal (UT) is a single-antenna device. The channel estimation method uses the information ca...
Evaluation of ultrasonic aluminium degassing by piezoelectric sensor
Puga, Hélder; Gabriel, Joaquim; Barbosa, J.; Seabra, Eurico; Ribeiro, Carlos Silva; Prokic, MiodragThe purpose of this work was the development of a reliable technique to evaluate the intensity of acoustic cavitation during degassing of aluminium melts and to use it to select the optimum processing time for an envisaged degassing efficiency. A high sensitivity piezoelectric disk type device was used as a sensing feedback in water and liquid AlSi9Cu3 alloy. The signal acquisition and processing was carried ou...
Effect of melting pressure and superheating on chemical composition and contami...
Gomes, Fernando; Puga, Hélder; Barbosa, J.; Ribeiro, Carlos SilvaWhen melting reactive alloys, chemical composition and alloy homogeneity strongly depend on processing conditions, especially if melting is performed in ceramic crucibles. In this case, the nature of crucible materials, the melting stock composition and the melting parameters (atmosphere, pressure, superheating time and temperature) are critical processing variables. In this work, a Ti–48Al alloy was induction ...
The combined effect of melt stirring and ultrasonic agitation on the degassing ...
Puga, Hélder; Barbosa, J.; Teixeira, J. Carlos; Seabra, Eurico; Ribeiro, Carlos Silva; Prokic, MiodragThe combined effect of high intensity ultrasound and melt stirring on the degassing of AlSi9Cu3 using simultaneously the novel MMM (Multi-frequency Multimode Modulated) ultrasonic technology to promote cavitation, and low frequency mechanical vibration to induce melt stirring, was studied. On a first stage single low frequency mechanical vibration experiments were carried out in water in order to visualize and ...
The inluence of processing variables on the ultrasonic degassing of molten AlSi...
Puga, Hélder; Barbosa, J.; Seabra, Eurico; Ribeiro, Carlos Silva; Prokic, MiodragThe effect of high intensity ultrasound on the degassing of AlSi9Cu3 alloy using the novelMMM(Multi-frequency Multimode Modulated) technology was studied. Different ultrasonic parameters (power and frequency), melt temperature and processing times were tested and their influence on the degassing efficiency evaluated. RPT (Reduced Pressure Test) was used to evaluate the hydrogen content in the alloys and the sam...
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