Sadek Crisostomo Absi Alfaro - Academia.edu (original) (raw)

Papers by Sadek Crisostomo Absi Alfaro

Sensors, Aug 13, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Direitos para esta edição cedidos à Atena Editora pelos autores. Open access publication by Atena... more Direitos para esta edição cedidos à Atena Editora pelos autores. Open access publication by Atena Editora Todo o conteúdo deste livro está licenciado sob uma Licença de Atribuição Creative Commons. Atribuição-Não-Comercial-NãoDerivativos 4.0 Internacional (CC BY-NC-ND 4.0). O conteúdo dos artigos e seus dados em sua forma, correção e confiabilidade são de responsabilidade exclusiva dos autores, inclusive não representam necessariamente a posição oficial da Atena Editora. Permitido o download da obra e o compartilhamento desde que sejam atribuídos créditos aos autores, mas sem a possibilidade de alterá-la de nenhuma forma ou utilizá-la para fins comerciais. Todos os manuscritos foram previamente submetidos à avaliação cega pelos pares, membros do Conselho Editorial desta Editora, tendo sido aprovados para a publicação com base em critérios de neutralidade e imparcialidade acadêmica. A Atena Editora é comprometida em garantir a integridade editorial em todas as etapas do processo de publicação, evitando plágio, dados ou resultados fraudulentos e impedindo que interesses financeiros comprometam os padrões éticos da publicação. Situações suspeitas de má conduta científica serão investigadas sob o mais alto padrão de rigor acadêmico e ético.

Proceedings of the ... International Congress of Mechanical Engineering, 2015

Sensors, Sep 15, 2016

Associated to the weld quality, the weld bead geometry is one of the most important parameters in... more Associated to the weld quality, the weld bead geometry is one of the most important parameters in welding processes. It is a significant requirement in a welding project, especially in automatic welding systems where a specific width, height, or penetration of weld bead is needed. This paper presents a novel technique for real-time measuring of the width and height of weld beads in gas metal arc welding (GMAW) using a single high-speed camera and a long-pass optical filter in a passive vision system. The measuring method is based on digital image processing techniques and the image calibration process is based on projective transformations. The measurement process takes less than 3 milliseconds per image, which allows a transfer rate of more than 300 frames per second. The proposed methodology can be used in any metal transfer mode of a gas metal arc welding process and does not have occlusion problems. The responses of the measurement system, presented here, are in a good agreement with off-line data collected by a common laser-based 3D scanner. Each measurement is compare using a statistical Welch's t-test of the null hypothesis, which, in any case, does not exceed the threshold of significance level α = 0.01, validating the results and the performance of the proposed vision system.

The Fifteenth International Offshore and Polar Engineering Conference, 2005

IntechOpen eBooks, Jan 14, 2021

Information contributes to the improvement of decision-making, process improvement, error detecti... more Information contributes to the improvement of decision-making, process improvement, error detection, and prevention. The new requirements of the coming Industry 4.0 will make these new information technologies help in the improvement and decision-making of industrial processes. In case of the welding processes, several techniques have been used. Welding processes can be analyzed as a stochastic system with several inputs and outputs. This allows a study with a data analysis perspective. Data mining processes, machine learning, deep learning, and reinforcement learning techniques have had good results in the analysis and control of systems as complex as the welding process. The increase of information acquisition and information quality by sensors developed at present, allows a large volume of data that benefits the analysis of these techniques. This research aims to make a bibliographic analysis of the techniques used in the welding area, the advantages that these new techniques can provide, and how some researchers are already using them. The chapter is organized according to some stages of the data mining process. This was defined with the objective of highlighting evolution and potential for each stage for welding processes.

This paper considers the identification problem of nonlinear systems based on single-hidden-layer... more This paper considers the identification problem of nonlinear systems based on single-hidden-layer neural networks (SHLNNs) and Lyapunov theory. A nonlinearly parameterized neural model, whose weights are adjusted by robust adaptive laws, which are designed via Lyapunov theory, is proposed for ensuring the convergence of the residual state error to an arbitrary neighborhood of zero. In addition, a scaling matrix is used to resize the unknown nonlinearities to be approximated by an SHLNN, which, in turn, provides a simple way to shape the residual state error. It is shown that all estimation errors are uniformly bounded and, in addition, that the residual state error is uniformly ultimately bounded with an ultimate bound that depends directly on some independent design parameters. To validate the theoretical results, the identification of a chaotic system and a comparison study with other work in the literature are performed.

Journal of The Brazilian Society of Mechanical Sciences and Engineering, Feb 28, 2018

In a recent research related to technological application in monitoring and control of welding, t... more In a recent research related to technological application in monitoring and control of welding, the use of various approaches to improve the productivity and quality through the development of techniques and automatic control systems is observed. This paper presents a methodology for modelling and control of the weld height reinforcement, allowing adjusting the process parameters, which can be implemented in the field of research or, in certain cases, in the industrial sector as an approach to the control of weld bead geometries. This was developed for the geometric characteristic studied in an integrated system of images acquisition, modelling and control system. The weld bead formation is measured through an acquisition system and processing of images using a low-cost web cam. The wire feed speed, the welding speed and voltage are predicted using an artificial neural network based on the desired weld height reinforcement. The control system is based on fuzzy logic. Keywords Gas metal arc welding (GMAW) Á Digital image processing Á Artificial neural networks Á Fuzzy logic

InTech eBooks, Dec 16, 2011

The International Journal of Advanced Manufacturing Technology, Nov 17, 2022

Gas metal arc welding (GMAW) process is one of the most important in the industry, so different e... more Gas metal arc welding (GMAW) process is one of the most important in the industry, so different efforts have been made to anticipate the parameters to convert this process into a stable one capable of joining parts with minimum human interference. In this sense, controlling is essential for automated applications because properties such as the weld mechanical strength are defined by the metal composition, the microstructure, and the weld bead geometry. Nevertheless, performing this automatic control to guarantee quality characteristics similar to a human expert's in mechanized welding systems is still tricky. Nowadays, although various sensors have been used in the monitoring for control, it is still hard to detect effective options to realtime identify geometry characteristics in the formation process of the welds. Furthermore, even today, a process much more complex is to control more than one parameter simultaneously or control the weld penetration using a single sensor. Then, this research describes two intelligence systems for real-time control of the weld bead geometry in the GMAW process. The first is a passive vision system with sensor fusion that controls the width and height; the second is an active vision system that controls the penetration. Results indicate that the proposed methodology can be applied to simultaneously control external geometrical parameters without a predefined model of the welding process. In the case of penetration, a fuzzy controller and a neural network-based model help the system adapt to input parameter variations throughout the welding process, thus correcting instabilities under changing operating conditions.

This paper proposes a scheme for secure telecommunication based on chaotic oscillators and Lyapun... more This paper proposes a scheme for secure telecommunication based on chaotic oscillators and Lyapunov theory. The presence of internal and external disturbances to increase the robustness of the method is considered in Lyapunov design. Another advantage of the proposed approach lies in that only one control input is required for synchronization of the master system with the slave system, making it relatively easy for application. Additionally, implementation via analog circuits of the proposed model is performed to validate the theoretical analysis.

Computers in Industry, Oct 1, 2019

Publisher: Elsevier NOTICE: this is the author's version of a work that was accepted for publicat... more Publisher: Elsevier NOTICE: this is the author's version of a work that was accepted for publication in Computers in Industry. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Computers in Industry, 111, (2019)

Electric arc welding is widely used in industrial processes, but its automation is limited by the... more Electric arc welding is widely used in industrial processes, but its automation is limited by the adverse environmental conditions in the periphery of the arc, which makes it difficult to measure the dimensions of the weld bead to close the control loop. Under these conditions, it is not possible to use conventional measuring systems. In this work, we describe a set of algorithms and hardware-software tools developed to obtain the data that allows to measure and estimate the geometry of the weld bead in this type of process. A data acquisition and open loop control system, a laser scanner and an algorithm to measure penetration using macrographic images of longitudinal cuts of the weld bead are developed. Most of these tools are characterized by their low cost, allowing their use in research and academic activities. The measurements are used to obtaining dynamic models of the weld bead geometry, using sensor fusion, in a conventional GMAW process with a constant voltage power source.

Journal of achievements in materials and manufacturing engineering, 2012

Purpose: The present research work has as purpose detecting perturbations, measuring and assessin... more Purpose: The present research work has as purpose detecting perturbations, measuring and assessing the welding stability in GMAW process in short circuit mode named hereafter as GMAW-S process. Design/methodology/approach: Welding trials were performed with a set of optimal input welding parameters. During experiments were induced some perturbations on the welding trajectory. It causes alteration on the stability of welding resulting as consequence geometrical shape deformations. During each experiments, acoustic emission signal coming from electric arc as well as arc voltage and welding current were acquired aided by a card acquisition and virtual instrumentation software. A heuristic model was performed as knowledge base rules of a fuzzy logic system. This system has two inputs and one output. Some additional welding trials were performed for assessing its performance. Findings: It was performed a welding stability assessment system based on fuzzy logic. As well as, this system is based on non-contact sensing what reduces the loading effects on the welding process. Research limitations/implications: In the present work was monitored just the acoustic emissions coming from arc. Although that, the results were satisfactory, an approach on data fusion of sensors including electromagnetic emission sensors could improve the quality assessments system. Originality/value: The non-contact welding stability assessment methods have reduces loading effects and a heuristic approach on the relations between arc emissions and welding stability allows quantifying nonlinear variables such as knowledge and experience of skilled welders, such that, it is possible to represent linguistic terms numerically what could be used as an on-line monitoring system of welding processes.

This work was aimed at establishing a model capable of being used in the selection of parameters ... more This work was aimed at establishing a model capable of being used in the selection of parameters for welding of butt joints up to 80mm thick with 10mm gap, using standard submerged arc welding equipment without oscillation. By studying the literature, undertaking some trial welds and analysing these welds, the initial range of parameters was obtained and used for modelling. Relationships between the welding parameters and the dimensions of the weld bead were found using such techniques as Factorial Design, Response Surface, Multiple Regression, Numerical Integration Techniques and Graphics Software Systems. Main and interactive effects of the welding parameters are calculated, allowing an estimation of the general weld bead geometric characteristics in narrow gap welding as a function of welding parameters such as current, voltage, welding speed, stand off, wire diameter and gap. Problems such as lack of fusion, removal of solidified slag and undercutting of the sidewall have been overcome. Sound wells in 50mm thick steel were obtained and conditions for welds in 70mm thick steel delineated.

Journal of achievements in materials and manufacturing engineering, 2007

ABSTRACT Purpose: In this work it will be carried through the filming of the formation and growth... more ABSTRACT Purpose: In this work it will be carried through the filming of the formation and growth of the nugget in resistance spot welding executed in AC and MF. A comparison for same times in both the processes will be carried through to verify which of the used processes offers better conditions, control and results as well as will help for one better understanding of the process aiming at the otimização.Design/methodology/approach: Two different spot welding machine (AC and MF-DC) had been used, and a digital high-speed camera. The weld points had been carried through in 3 galvanized steel different plate configurations. The electrodes had been truncated to obtain one better visualization for the weld nugget formation. The comparison of the formation and development between the weld point of each process (AC and MF) is shown in 7 pictures in the same values of time.Findings: For currents below 2 kA, no nugget was observed. and the formation of same after 10º cycle for bigger current of 3 kA. The MF-DC welding offers the possibility of obtaining nuggets more uniforms within shorter times (depending on the plate configuration).Research limitations/implications: In this work the AC machine is limited by the values of current of welding and pressure of the electrodes: (2 - 6) kA e (87 - 261) kgf respectively. Other materials: aluminum, stainless steel or material exactly dissimilar could be used following the line of this research. Bigger currents levels can also be used.Originality/value: The idea to compare resulted for the same process of welding under different conditions (equipment, materials and or parameters) makes possible the choice of these better conditions used to the otimização of the process.

Journal of achievements in materials and manufacturing engineering, 2011

Purpose: Show the relationship between geometric characteristics of the weld bead and the optical... more Purpose: Show the relationship between geometric characteristics of the weld bead and the optical-acoustic emissions from electric arc during welding in the GMAW-S process. Design/methodology/approach: Bead on plate welding experiments was carried out setting different process parameters. Every welding parameter group was set aiming to reach a high stability level what guarantee a geometrical uniformity in the weld beads. In each experiment was simultaneously acquired arc voltage, welding current, infrared and acoustic emissions; from them were computed parameters as arc power, acoustic peaks rate and infrared radiation rate. It was used a tri-dimensional LASER scanner for to acquire geometrical information from the weld beads surface as width and height of the bead. Depth penetration was measured from sectional cross cutting of weld beads. Findings: Previous analysis showed that the arc emission parameters reach a stationary state with different characteristic for each experiment group which means that there is some correlation level between them. Posterior analysis showed that from infrared parameter is possible to monitoring external weld bead geometry and principally its penetration depth. From acoustic parameter is possible to monitoring principally the external weld bead geometry. Therefore is concluded that there is a close relation between the arc emissions and the weld bead geometry and that them could be used to measuring the welding geometrical parameters. Research limitations/implications: After analysis it was noticed that the infrared sensing has a better performance than acoustic sensing in the depth penetration monitoring. Infrared sensing also sources some information about external geometric parameters that in conjunction with the acoustic sensing is possible to have reliable information about weld bead geometry. This method of sensing geometric parameters could be applied in other welding processes, but is necessary to have visibility of the arc, it means that for example this method cannot be used in the submerged arc welding-SAW process. Originality/value: The using two or more sensors for monitoring welding parameters increases the performance and reliability of the measurements. In this case, the monitoring of the weld bead geometric parameters could be possible from sensing arc emission and potentially it could be used as an on-line monitor, avoiding any complex electric connections of sensors into the welding process.

Welding - Materials, Fabrication Processes, and Industry 4.0 [Working Title]

Gas metal arc welding (GMAW) processes need to guarantee the quality of the parts produced from t... more Gas metal arc welding (GMAW) processes need to guarantee the quality of the parts produced from this stability in the manufacture of a single bead. In addition to the visual inspection and subsequent characterization with the cutting of the samples, which consists of destructive analysis, it is possible to monitor the entire process and the quality of the part in a non-destructive way. Therefore, this work aims to develop a methodology for the analysis of non-destructive and online weld beads using high-speed cameras, thermal cameras, profilometer and algorithms in MatLab for data processing. The high-speed cameras allow the capture of images of the electric arc and the metallic transfer mode. The thermal cameras, on the other hand, allow the visualization of the melt pool and the temperatures reached during the deposition. Finally, the laser profilometer allows you to make a point cloud of the part and measure its geometry (height, width, height-to-width ratio, wetting angle) onlin...