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167 results on '"Costa, Henara"'

4. Influence of the Counter-Body Material on Micro-Abrasion-Corrosion

Author

Biasoli de Mello, José Daniel, Ardila, Miguel Angel Narvaes, Costa, Henara Lilian, Ceccarelli, Marco, Series Editor, Corves, Burkhard, Advisory Editor, Glazunov, Victor, Advisory Editor, Hernández, Alfonso, Advisory Editor, Huang, Tian, Advisory Editor, Jauregui Correa, Juan Carlos, Advisory Editor, Takeda, Yukio, Advisory Editor, Agrawal, Sunil K., Advisory Editor, Ciulli, Enrico, editor, and Ruggiero, Alessandro, editor

Published
2024
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20. Effect of Oil Acoustic Properties on Film Thickness Measurement by Ultrasound Using Spring and Resonance Models.

Author

Piovesan, Alvaro S., Schirru, Michele, Tatzgern, Fabio, Medeiros, Jorge L. B., and Costa, Henara L.

Subjects
THICKNESS measurement, RESONANCE, OPTICAL measurements, SPEED of sound, ULTRASONIC waves
Abstract

The principle of reflection of ultrasonic waves at lubricated interfaces has been widely studied in recent years using different models. In this work, two different models (the spring model and the resonance model) were used to verify the influence of the acoustic properties of four different lubricating oils. A simple three-layer configuration was used, where carefully prepared, well-controlled gaps between stainless steel plates were established to accommodate a drop of oil. Optical measurements showed that the gaps formed were: gap 1 = 11 µm, gap 2 = 85 µm, gap 3 = 100 µm, and gap 4 = 170 µm. The smaller gap (11 µm) was found to be in the limit measurement range using the spring model for the sensor used in this work (14 MHz), whereas the resonance method was used for the thicker gaps. For the resonance model, the use of the phase spectra helped the identification of the resonance frequencies. The results showed good agreement between the measured thicknesses and the nominal gap values. There was little effect of the acoustic properties of the oils on the measured values, with the largest discrepancies found for the oil with the highest speed of sound (PAO4). This new way to characterize oil properties in a thin gap, where the material and geometry of the contact are fully characterized, enables us to compare different measurement methods and understand their sensitivity when testing similar materials of the same class of lubricants, as small deviations are crucial in real-life applications. [ABSTRACT FROM AUTHOR]

Published
2024
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22. Modification of surface topography : manufacturing methods and applications

Author

Costa, Henara Lillian

Subjects
621.89
Abstract

Six texturing methods were investigated experimentally. Some were used to produce samples or tools, although they are already conventional texturing methods. The innovative techniques proposed were developed to different extents. In particular, two techniques were proposed and investigated in detail: maskless electrochemical texturing, and the use of inkjet printing to mask metal surfaces before chemical texturing. A great number of applications could be proposed for surface texturing. For each application, design requirements help to decide which methods should be used to texture the surfaces involved. The main application for surface texturing investigated in this work was the increase of tribological performance under lubricated sliding conditions. Carbon steel samples with different geometrical surface patterns were tested in lubricated reciprocating sliding tests. Low normal loads guaranteed that elastic deformation was very small. The intrinsic variable speed of the test allowed the investigation of different regimes of lubrication, although the analysis mainly focused in the regions of maximum speed, where full film lubrication prevails. Different normal loads were tested. The effect on friction force and film thickness of the size, shape and distribution of the features that compose the patterns was established. Patterns containing chevrons with the vertex oriented along the sliding direction resulted in the largest increase of the film thickness due to increase of hydrodynamic pressure. Strip drawing tests were also used, in order to evaluate the effect of texturing in conditions involving plastic deformation. Significant variation of friction force was observed between different textures.

Published
2005

29. Quantification of Alumina Evaporation by Thermal Plasma

Author

de Castro, Franciele Dias, Fonseca, Marcelo Gauterio, Pineiro, Mariana Obiedo, Collares, Magno P., and Costa, Henara L.

Abstract

When using powder particles in thermal plasma processes, partial evaporation of the particles may occur during the plasma–particle interaction. This research proposed the study of the parameters that cause evaporation with the aid of an experimental setup for the validation of an analytical model. To quantify evaporation, two experiments were carried out: the first one involved deposition of a coating on a substrate, and the second one without deposition. The model showed differences in evaporation when the interaction of the particles with the photons emitted by the plasma is considered. The particle radius size can influence the photon absorption efficiency and the electron emission current from the particle surface during the process. This can cause an increase in the final evaporation rate. In this research, evaporation was obtained as a function of the injected plasma mass considering the different particle size distributions. The experiments showed significant evaporation during thermal plasma processing of alumina powder, but evaporation reduced for higher feed rates.

Published
2024
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45. Efeito da energia de soldagem sobre a microestrutura e resistência à corrosão de revestimentos de Inconel 625 aplicados pelo processo GMAW

Author

Souza,Daniel, Tavares,Amanda Figueira, Costa,Henara Lillian, and Osorio,Alice Gonçalves

Subjects
microestrutura, revestimentos, GMAW, corrosão, Inconel
Abstract

RESUMO A liga de Inconel 625 é uma superliga à base de níquel altamente resistente à corrosão particularmente utilizada na forme de revestimentos sobre um substrato menos nobre. Existem inúmeras formas de aplicação deste material, sendo uma delas o uso de processos de soldagem. Tradicionalmente faz-se uso de processos de deposição por soldagem que promovam baixa diluição (menor contaminação do Inconel com o material do substrato), mas estes processos possuem característica de baixa produtividade devido às baixas taxas de deposição empregadas. Assim, este estudo tem como objetivo avaliar a aplicação de Inconel 625 utilizando o processo GMAW com diferentes energias de soldagem, que possibilita operar com altas taxas de deposição, mas com o inconveniente de promover alta diluição. Para isso, revestimentos foram depositados com três níveis de energias de soldagem, avaliando seus efeitos sobre a microestrutura e a resistência à corrosão dos depósitos. As macros e microestruturas dos depósitos foram avaliadas por microscopia óptica, microscopia eletrônica de varredura (MEV), espectrometria de energia dispersa (EDS) e difração de raios-X (DRX). Foram medidas a diluição, os espaçamentos dendríticos secundários e avaliadas as microestruturas. A resistência à corrosão dos depósitos foi avaliada por ensaios de polarização potenciodinâmica cíclica. Os resultados mostraram que a relação entre energia de soldagem e diluição dependem da amplitude de tecimento. Observou-se também que a energia de soldagem afetou a quantidade de fases, sendo que energias mais baixas produziram estruturas dendríticas mais refinadas. Além disso, o estudo mostrou que os ensaios de corrosão realizados a temperatura de 25 ºC não promoveram corrosão superficial nas amostras independente da energia de soldagem imposta ao revestimento e que os ensaios a 60 º C causaram corrosão em todas as condições.

Published
2020

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