Prof. Ezequiel Pessoa

LeTourneau University

Prof. Ezequiel Pessoa

LeTourneau University

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Academic Career Length

17Years (2010-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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6 November 2020 in Materials

Journal Article

The Effect of Polarity and Hydrostatic Pressure on Operational Characteristics of Rutile Electrode in Underwater Welding

ANDRES M MORENO URIBE

Alexandre Q. Bracarense

Ezequiel Pessoa

In order to provide a better understanding of the phenomena that define the weld bead penetration and melting rate of consumables in underwater welding, welds were developed with a rutile electrode in air welding conditions and at the simulated depths of 5 and 10 m with the use of a hyperbaric chamber and a gravity feeding system. In this way, voltage and current signals were acquired. Data processing involved the welding voltage, determination of the sum of the anodic and cathodic drops, calculation of the short-circuit factor, and determination of the melting rate. Cross-sectional samples were also taken from the weld bead to assess bead geometry. As a result, the collected data show that the generation of energy in the arc–electrode connection in direct polarity (direct current electrode negative-DCEN) is affected by the hydrostatic pressure, causing a loss of fusion efficiency, a drop of operating voltage, decreased arc length, and increased number of short-circuit events. The combination of these characteristics kept the weld bead geometry unchanged, compared to dry weld conditions. With the positive electrode (direct current electrode positive-DCEP), radial losses were derived from greater arc lengths resulting from increasing hydrostatic pressure, which led to a decrease in weld penetration.

27 September 2022 in Journal of Materials Research and Technology

Journal Article

Development of oxyrutile low alloy ferritic electrode for wet welding

R.R. Marinho

M.J. Monteiro

1 August 2021 in Journal of Materials Processing Technology

Journal Article

Effect of the welding angle on the porosity of underwater wet welds performed in overhead position at different simulated depths

Luis Edmundo Ramírez Luna

Alexandre Queiroz Bracarense

Ezequiel Pessoa

Patricia Sheilla Costa

Gerardo Altamirano Guerrero

Antonio Enrique Salas Reyes

1 June 2010 in Soldagem & Inspeção

Journal Article

Efeito do teor de carbono do metal de base e da alma do eletrodo revestido sobre a porosidade em soldas molhadas

Luciano G. D. Andrade

Weslley C. Dias

Leandro F. Ribeiro

Alexandre Q. Bracarense

Ezequiel Pessoa

Stephen Liu

Porosidade é um defeito comum em soldagem subaquática molhada. Vários estudos têm sido realizados com o objetivo de avaliar os mecanismos que controlam sua formação e assim encontrar soluções para minimizá-la ou eliminá-la. Este trabalho tem como objetivo avaliar o efeito da variação dos teores de carbono do metal de base e da alma do eletrodo sobre a porosidade do metal de solda. Dois diferentes metais de base, com variações apenas no teor de carbono (C2 - 0,1% e C7 - 0,7%), foram utilizados para deposição das soldas feitas à 50 metros de profundidade, utilizando eletrodos comerciais E6013 com diferentes teores de carbono na alma (E2 - 0,002% e E6 -0,6%), em polaridade direta (DCEN). O método macrográfico de análise de imagens foi utilizado para a quantificação da porosidade. Utilizando os metais de base C2 e C7, observou-se que a porosidade aumentou significativamente com o aumento do teor de carbono da alma do eletrodo. Em contrapartida, observou-se uma redução da porosidade com o aumento do teor de carbono do metal de base utilizando-se os eletrodos E2 e E6.

1 January 2020 in Soldagem & Inspeção

Journal Article

Efeito da Técnica de Esmerilhamento do Cordão na Dureza da ZTA de Soldas Multipasses Subaquáticas Molhadas

Gabriel Mendes de Almeida Carvalho

Alexandre Queiroz Bracarense

Ezequiel Pessoa

Caroline Nazaré Gonçalves

Resumo: A Soldagem Subaquática Molhada com Eletrodo Revestido (SMER) tem sido vastamente utilizada devido ao seu baixo custo em relação a outros processos aplicados debaixo d'água e por alcançar resultados de boa qualidade. Um dos principais problemas encontrados é a perda de ductilidade na Zona Termicamente Afetada (ZTA) devido ao rápido resfriamento. Uma opção para a redução da dureza e consequente aumento da ductilidade é a aplicação de um Tratamento Térmico Pós-Soldagem (TTPS). Entretanto, sua utilização por vezes se torna impraticável no ambiente subaquático. Uma alternativa é a utilização do próprio calor proveniente de passes subsequentes, promovendo o revenimento de regiões endurecidas (técnica do passe de revenimento). Neste trabalho foi estudado o efeito do esmerilhamento do cordão de solda após cada passe, visando otimizar o calor de passes subsequentes e controlar a dureza da ZTA no processo de soldagem molhada. Todas as soldas foram realizadas em um tanque hiperbárico simulando a profundidade de 10 m. Os resultados demonstraram que quando utilizada a técnica do esmerilhamento, o calor do passe subsequente é melhor utilizado e o revenimento promove o amaciamento de toda a extensão da ZTA, alcançando menores valores de dureza em relação ao processo convencional e dentro dos limites estabelecidos por normas reguladoras.

1 January 2010

Conference Paper

Evaluation and Development of Electrodes for Wet Welding of Structural Ship Steels

Valter R. Santos

Mauri´cio J. Monteiro

Fernando C. R. Assunc¸a¯o

Alexandre Q. Bracarense

Ezequiel Pessoa

Leonardo A. Vieira

To better understand the behavior of some commercial wet welding electrodes down to 20 m equivalent water depth as well as to develop a new electrode, a research program was initiated in 2007. This depth is considered the maximum expected in the in situ repair of structural parts of floating production units. The weld metal evaluation was done by microstructural characterization, Vickers hardness, Charpy and tensile tests, chemical analysis, and diffusible hydrogen measurement. The influences of pressure on the mechanical properties of the weld metal are presented and discussed on the basis of chemical composition, microstructure and porosity. The electrode under development showed promising results concerning the possibility to broaden the range of qualified welding procedures. This expectation is based on the good results of diffusible hydrogen, porosity, impact toughness and ductility down to 20 m equivalent water depth. The susceptibility of hydrogen cracking in weld metal and in heat affected zone was estimated comparatively. The presence of hydrogen cracks is discussed as an important limiting factor for the qualification of welding procedures in the class A of the AWS D3.6M:1999 specification.

About Me

Ezequiel Pessoa is a full-time Professor in the Department of Welding/Materials Joining Engineering at LeTourneau University, where he has been since 2019. During 2018 he was a Visiting Professor at Colorado School of Mines, Golden, Colorado. From 2007 to 2018 he worked as full-time Tenured Professor at Federal Institute of Minas Gerais (IFMG), Minas Gerais, Brazil. During 2006-2007 he was a Laboratory Engineer at Laboratório de Robótica, Soldagem e Simulação of Federal University of Minas Gerais (UFMG) in Brazil. He received a B.S. from Federal University of Minas Gerais in 2001, and an M.S. and Ph.D. in Mechanical Engineering from the same University (UFMG) in 2003 and 2007 respectively. During 2006 he was a research fellow at Center for Welding Joining and Coatings Research (CWJCR) of Colorado School of Mines, Golden, Colorado. His research interests span both applied welding procedure development and welding consumables development. Much of his work has been on underwater wet welding (UWW) field, mainly through the application of special equipment, welder training technics and also Shielded Metal Arc Welding consumable development. In the welding procedure development, he has worked on the application of welding technics and parameters in order to achieve Class A (structural) welding. He has explored the effects of welding technics, special equipment application and parameters on welding defects, such porosity and cracks, and mechanical properties.

Prof. Ezequiel Pessoa

Prof. Ezequiel Pessoa

Research Focus & Metrics

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