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Self-mated tribological systems based on multilayer micro/nanocrystalline CVD d...
Salgueiredo, E.; Abreu, C. S.; Amaral, M.; Oliveira, F. J.; Gomes, J. R.; Silva, R. F.The tribological response of multilayer micro/nanocrystalline diamond coatings grown by the hot filament CVD technique is investigated. These multigrade systems were tailored to comprise a starting microcrystalline diamond (MCD) layer with high adhesion to a silicon nitride (Si3N4) ceramic substrate, and a top nanocrystalline diamond (NCD) layer with reduced surface roughness. Tribological tests were carried ou...
A DLC/diamond bilayer approach for reducing the initial friction towards a high...
Amaral, M.; Carreira, D. J; Fernandes, A. J. S.; Abreu, C. S.; Oliveira, F. J.; Gomes, J. R.; Silva, R. F.Sliding contact mechanics is used to account for the net increase of the bearing capacity of high wear-resistant CVD diamond coatings when an outer layer of a DLC lubricant film is deposited on their top surface. Experimental results,namely the critical failure load, taken from reciprocating ball-on-plate tribological testing of such DLC/diamond bilayers, are on the basis of this statement. DC magnetron sputter...
Strength improvement of adhesively-bonded joints using a reverse-bent geometry
Campilho, Raul; Pinto, A. M. G.; Banea, Mariana D.; Silva, R. F.; Silva, Lucas F. M. daAdhesive bonding of components has become more efficient in recent years due to the developments in adhesive technology, which has resulted in higher peel and shear strengths, and also in allowable ductility up to failure. As a result, fastening and riveting methods are being progressively replaced by adhesive bonding, allowing a big step towards stronger and lighter unions. However, single-lap bonded joints st...
Tensile behaviour of single and double-strap repairs on aluminium structures
Pinto, A. M. G.; Campilho, Raul; Mendes, Isabel R.; Silva, R. F.; Magalhães, A. G.; Baptista, A. P. M.In this work, an experimental study was performed on the influence of plug filling, loading rate and temperature on the tensile strength of single-strap (SS) and double-strap (DS) repairs on aluminium structures. The experimental programme includes repairs with different values of overlap length (LO=10, 20 and 30 mm), and with and without plug filling. The influence of the testing speed on the repairs streng...
Estudo de características de produção de matrizes de corte por meio da análise ...
Yamaki,M.; Menezes,G.R.O.; Paiva,A.L.C.; Barbosa,L.; Silva,R.F.; Teixeira,R.B.; Torres,R.A.; Lopes,P.S.Avaliou-se o descarte de variáveis de produção, em análises de componentes principais, de três linhagens de matrizes de corte do Programa de Melhoramento Genético da Universidade Federal de Viçosa, utilizando informações de 270 aves, sendo 90 de cada linhagem. As características analisadas foram dias para postura do primeiro ovo (DPPO), taxa de postura da 22ª a 56ª semana (TP), peso médio individual na 32ª (PMI...
Obese obstructive sleep apnea patients with tonsil hypertrophy submitted to ton...
Martinho,F.L.; Zonato,A.I.; Bittencourt,L.R.A.; Soares,M.C.M.; Silva,R.F.N.; Gregório,L.C.; Tufik,S.The physiopathology of obstructive sleep apnea-hypopnea syndrome (OSAHS) is multifactorial and obesity has been shown to be one of the main factors correlated with its occurrence. In obese patients with anatomical alterations of the upper airways it is often difficult to predict success for surgical correction since obesity is a limiting factor. Therefore, the aim of the present study was to evaluate the result...
Tribological testing of self-mated nanocrystalline diamond coatings on Si3N 4 c...
Abreu, C. S.; Amaral, M.; Oliveira, F. J.; Tallaire, A.; Bénédic, F.; Syll, O.; Cicala, G.; Gomes, J. R.; Silva, R. F.Due to their much lower surface roughness compared to that of microcrystalline diamond, nanocrystalline diamond (NCD) films are promising candidates for tribological applications in particular when deposited on hard ceramic materials such as silicon nitride (Si3N4). In the present work, microwave plasma assisted chemical vapour deposition of NCD is achieved using Ar/H2/CH4 gas mixtures on plates and ball-shaped...
In-situ friction monitoring of self-mated CVD diamond coatings using acoustic e...
Abreu, C. S.; Oliveira, F. J.; Gomes, J. R.; Belmonte, M.; Fernandes, A. J. S.; Silva, R. F.In-situ measurements of acoustic emission (AE) in self-mated tribological pairs of CVD diamond coated silicon nitride (Si3N4) were made with the purpose of investigating the relationship between AE signal and friction events. A good correlation is found between the energy dissipation/emission processes, therefore enabling the possibility of monitoring the different friction regimes occurring during the sliding ...
CVD diamond coated silicon nitride self-mated systems : tribological behaviour ...
Abreu, C. S.; Oliveira, F. J.; Belmonte, M.; Fernandes, A. J. S.; Gomes, J. R.; Silva, R. F.Friction and wear behaviour of self-mated chemical vapour deposited (CVD) diamond films coating silicon nitride ceramics (Si3N4) were investigated in ambient atmosphere. The tribological tests were conducted in a reciprocal motion ball-on-flat type tribometer under applied normal loads up to 80 N (~10 GPa). Several characterisation techniques - including scanning electron microscopy (SEM), atomic force microscopy...
Friction and wear performance of HFCVD nanocrystalline diamond coated silicon n...
Abreu, C. S.; Amaral, M.; Fernandes, A. J. S.; Oliveira, F. J.; Silva, R. F.; Gomes, J. R.Silicon nitride (Si3N4) ceramics were selected as substrates due to their thermal and chemical compatibility to diamond that ensure the adequate NCD adhesion for mechanical purposes. NCD deposition was performed by hot-filament chemical vapour method (HFCVD) using Ar/H2/CH4 gas mixtures. The tribological assessment of homologous pairs of NCD films was accomplished using reciprocating ball-on-flat tests using NC...
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