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  • 1.
    Cruz-Crespo, Amado
    et al.
    Universidad Central "Marta Abreu" de Las Villas, Universidade Federal de Uberlandia.
    Gonzalez, Lorenzo Perdomo
    Anim Hlth & Vet Labs Agcy, VLA Lasswade Vet Labs Agcy Lasswade, King Abdulaziz University.
    Rafael, Quintana
    Universidad Central "Marta Abreu" de Las Villas.
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Universidade Federal de Uberlandia University West - Sweden Fed Univ Uberlandia UFU.
    Flux for Hardfacing by Submerged Arc Welding from Ferrochrome-manganese and Slag from the Simultaneous Reduction of Chromite and Pyrolusite2019Inngår i: Soldagem & Inspeção, ISSN 0104-9224, E-ISSN 1980-6973, Vol. 24, artikkel-id e2424Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The obtaining of a flux for hardfacing by Submerged Arc Welding (SAW), using ferrochrome-manganese and slag obtained from the simultaneous carbothermal reduction of chromite and pyrolusite is addressed. The ferrochrome-manganese and the slag were obtained, conceiving that both products satisfy the requirements of the components (alloy system and matrix) of an agglomerated flux for hardfacing. The fusion-reduction process to obtain the alloy and the slag was carried out in a direct current electric arc furnace. The pouring was carried out into water to facilitate the separation and grinding of the cast products. An experimental flux was manufactured, using the obtained alloy and slag. Deposits were obtained by SAW, which were characterized in terms of: chemical composition, microstructure and hardness. It was concluded that the flux obtained from ferrochrome-manganese and slag from the simultaneous carbothermal reduction of chromite and pyrolusite, allows to deposit an appropriate metal for work under abrasion conditions, characterized by significant carbon and chromium contents and a martensitic microstructure predominantly, with hardness of 63 HRc.

  • 2.
    da Silva, Leandro Joao
    et al.
    Center for Research and Development of Welding Processes (Laprosolda), Federal University of Uberlandia (UFU), Uberlândia (BRA).
    Teixeira, Felipe Ribeiro
    Center for Research and Development of Welding Processes (Laprosolda), Federal University of Uberlandia (UFU), Uberlândia (BRA).
    Araujo, Douglas Bezerra
    Center for Research and Development of Welding Processes (Laprosolda), Federal University of Uberlandia (UFU), Uberlândia (BRA).
    Reis, Ruham Pablo
    Center for Research and Development of Welding Processes (Laprosolda), Federal University of Uberlandia (UFU), Uberlândia (BRA).
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Center for Research and Development of Welding Processes (Laprosolda), Federal University of Uberlandia (UFU), Uberlândia (BRA).
    Work Envelope Expansion and Parametric Optimization in WAAM with Relative Density and Surface Aspect as Quality Constraints: The Case of Al5Mg Thin Walls with Active Cooling2021Inngår i: JOURNAL OF MANUFACTURING AND MATERIALS PROCESSING, E-ISSN 2504-4494, Vol. 5, nr 2Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The successful and efficient production of parts with specific features by Wire + Arc Additive Manufacturing (WAAM) strongly depends on the selection of proper and typically interrelated deposition parameters. This task might be particularly challenging in the making of thin walls, which might be highly impacted by processing conditions and heat accumulation. In this context, this study aims at expanding the work envelope and optimizing the parametric conditions in WAAM with relative density and surface aspects of the preforms as quality constraints. The experimental approach was based on the deposition of thin Al5Mg walls by the CMT process on its standard welding setup and with an active cooling technique to enhance the deposition robustness. Internal voids were estimated by Archimedes’ method. The surface quality of the walls was assessed through the visual aspect and the surface waviness by cross-section analysis. All the conditions presented relative density higher than 98%. The upgrade of the standard welding hardware to WAAM purposes through the addition of a supplementary shielding gas nozzle to the torch and the intensity of the heat sinking from the part significantly expanded the process work envelope, with its applicability being successfully demonstrated with multi-objective optimization. To sum up, a decision-making procedure is presented towards achieving intended preform quality.

    Fulltekst (pdf)
    fulltext
  • 3.
    da Silva, Leandro João
    et al.
    Center for Research and Development of Welding Processes (Laprosolda), Department of Mechanical Engineering, Federal University of Uberlandia (UFU), Uberlândia (BRA).
    Ferraresi, Henrique Nardon
    Center for Research and Development of Welding Processes (Laprosolda), Department of Mechanical Engineering, Federal University of Uberlandia (UFU), Uberlândia (BRA).
    Araújo, Douglas Bezerra
    Center for Research and Development of Welding Processes (Laprosolda), Department of Mechanical Engineering, Federal University of Uberlandia (UFU), Uberlândia (BRA).
    Reis, Reis Pablo
    Center for Research and Development of Welding Processes (Laprosolda), Department of Mechanical Engineering, Federal University of Uberlandia (UFU), Uberlândia (BRA).
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Center for Research and Development of Welding Processes (Laprosolda), Department of Mechanical Engineering, Federal University of Uberlandia (UFU), Uberlândia (BRA).
    Effect of thermal management approaches on geometry and productivity of thin-walled structures of er 5356 built by wire + arc additive manufacturing2021Inngår i: Coatings, ISSN 2079-6412, Vol. 11, nr 9Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The present paper aimed at assessing the effect of two thermal management approaches on geometry and productivity of thin-walled structures built by Wire + Arc Additive Manufacturing (WAAM). Thin-walls of ER 5356 (Al5Mg) with different lengths and the same number of layers were deposited via the gas metal arc (GMA) process with the aid of an active cooling technique (near-immersion active cooling-NIAC) under a fixed set of deposition parameters. Then, the same experiment was performed with natural cooling (NC) in air. To characterize the thermal management approaches, the interpass temperature (i.e., the temperature at which subsequent layers are deposited) were monitored by a trailing/leading infrared pyrometer during the deposition time. Finally, thin walls with a fixed length were deposited using the NC and NIAC approaches with equivalent interpass temperatures. As expected, the shorter the wall length the more intense the deposition concentration, heat accumulation, and, thus, geometric deviation. This behavior was more evident and premature for the NC strategy due to its lower heat sinking effectiveness. The main finding was that, regardless of the thermal management technique applied, if the same interpass temperature is selected and maintained, the geometry of the part being built tends to be stable and very similar. However, the total deposition time is somewhat shorter with the NIAC technique due its greater heat sinking advantage. Thus, the NIAC technique facilitates the non-stop manufacturing of small parts and details via WAAM. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

    Fulltekst (pdf)
    Coatings
  • 4.
    da Silva, Leandro João
    et al.
    SENAI Innovation Institute for Manufacturing Systems and Laser Processing, Joinville, SC, Brazil (BRA); Federal University of Uberlândia (UFU), Laprosolda – Center for Research and Development of Welding,Processes, Uberlandia, MG, Brazil (BRA).
    Souza, Danielle Monteiro
    Federal University of Uberlândia (UFU), Laprosolda – Center for Research and Development of Welding,Processes, Uberlandia, MG, Brazil (BRA).
    de Araújo, Douglas Bezerra
    Federal University of Uberlândia (UFU), Laprosolda – Center for Research and Development of Welding,Processes, Uberlandia, MG, Brazil (BRA).
    Reis, Ruham Pablo
    Federal University of Uberlândia (UFU), Laprosolda – Center for Research and Development of Welding,Processes, Uberlandia, MG, Brazil (BRA).
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Federal University of Uberlândia (UFU), Laprosolda – Center for Research and Development of Welding,Processes, Uberlandia, MG, Brazil (BRA).
    Concept and validation of an active cooling technique to mitigate heat accumulation in WAAM2020Inngår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 107, nr 5-6, s. 2513-2523Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This work aimed at introducing and exploring the potential of a thermal management technique, named as near-immersion active cooling (NIAC), to mitigate heat accumulation in Wire + Arc Additive Manufacturing (WAAM). According to this technique concept, the preform is deposited inside a work tank that is filled with water, whose level rises while the metal layers are deposited. For validation of the NIAC technique, Al5Mg single-pass multi-layer linear walls were deposited by the CMT® process under different thermal management approaches. During depositions, the temperature history of the preforms was measured. Porosity was assessed as a means of analyzing the potential negative effect of the water cooling in the NIAC technique. The preform geometry and mechanical properties were also assessed. The results showed that the NIAC technique was efficient to mitigate heat accumulation in WAAM of aluminum. The temperature of the preforms was kept low independently of its height. There was no measurable increase in porosity with the water cooling. In addition, the wall width was virtually constant, and the anisotropy of mechanical properties tends to be reduced, characterizing a preform quality improvement. Thus, the NIAC technique offers an efficient and low-cost thermal management approach to mitigate heat accumulation in WAAM and, consequently, also to cope with the deleterious issues related to such emerging alternative of additive manufacturing.

  • 5.
    Dahat, Shubham
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Hurtig, Kjell
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    A Methodology to Parameterize Wire + Arc Additive Manufacturing: A Case Study for Wall Quality Analysis2020Inngår i: Journal of Manufacturing and Materials Processing, ISSN 2504-4494, Vol. 4, nr 1, artikkel-id 4010014Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The objective of this work was the development of a methodology to parametrize wire + arc additive manufacturing (WAAM), aiming dimension repeatability, and tolerances. Parametrization of WAAM is a difficult task, because multiple parameters are involved and parameters are inter-dependent on each other, making overall process complex. An approach to study WAAM would be through operational maps. The choice of current (Im) and travel speed (TS) for the desirable layer width (LW) determines a parametrization that leads to either more material or less material to be removed in post-operations, which is case study chosen for this work. The work development had four stages. First stage, named ‘mock design’, had the objective of visualizing the expected map and reduce further number of experiments. At the second stage, ‘pre-requisite for realistic operational map’, the objective was to determine the operating limits of TS and Im with the chosen consumables and equipment. Within the ‘realistic operational map’ stage, a design for the experiments was applied to cover a parametric area (working envelope) already defined in the previous stage and long and tall walls were additively manufactured. Actual values of LW (external and effective layer width) were measured and an actual operating envelope was reached. According to the geometry-oriented case study, a surface waviness index (SWindex) was defined, determined, and overlapped in the envelope. It was observed that the walls with parameters near the travel speed limits presented higher SWindex. This operational map was further validated (fourth stage) by selecting a target LW and finding corresponding three parametric set (covering the whole range of operational map) to produce walls on which geometry characterization was carried out. After geometry characterization, obtained LW was compared with the target LW (the maximum values were very tied, with deviations from +0.3 to 0.5 mm), with a SWindex deviation at the order of 0.05. Both results evidence high reproductivity of the process, validating the proposed methodology to parametrize WAAM.

    Fulltekst (pdf)
    fulltext
  • 6.
    de Souza Amaral, Thiago
    et al.
    CBMM, Araxá, MG, Brasil.
    Carboneri Carboni, Marcelo
    CBMM, São Paulo, SP, Brasil.
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Universidade Federal de Uberlândia – UFU, Uberlândia, MG, Bras.
    Avaliação da Aplicação de um Atlas de Soldagem de um Aço Bainítico Microligado ao Nióbio: Application Assessment of a Welding Atlas of a Niobium Microalloyed Bainitic Steel2017Inngår i: Soldagem & Inspeção, ISSN 0104-9224, E-ISSN 1980-6973, Vol. 22, nr 2, s. 163-173Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [pt]

    Os aços de alta resistência microligados ao nióbio têm mostrado ser uma boa opção para fabricação de perfis estruturais, utilizando os conceitos já desenvolvidos para a indústria de gás e óleo. Entretanto, a definição das reais necessidades em termos de soldagem desta família de aços não está bem descrita nas normas de soldagem mais utilizadas pelo setor. Este trabalho demonstra a construção e avaliação de um Atlas de Soldagem produzido através de simulações físicas (Gleeble e dilatometria) e ensaios mecânicos de amostras simuladas. O objetivo é que o atlas de soldagem seja uma ferramenta orientativa para melhor definição das faixas de parâmetros para soldagem desta classe de material. A metodologia proposta foi aplicada a um aço ARBL bainítico da classe 65 ksi. Foi possível determinar com mais segurança a faixa de energia de soldagem recomendada, inclusive quanto à necessidade ou não do uso de pré-aquecimento, e evidenciar que as simulações são comparáveis a soldas reais. Esta abordagem mostrou trazer benefícios, como redução de custos com processo de pré-aquecimento desnecessário.

  • 7.
    dos Santos Paes, Luiz Eduardo
    et al.
    Federal University of Santa Catarina, Department of Mechanical Engineering, Laboratory of Precision Engineering, Laser Division (LMP-Laser), Florianópolis, Brazil (BRA).
    Pereira, Milton
    Federal University of Santa Catarina, Department of Mechanical Engineering, Laboratory of Precision Engineering, Laser Division (LMP-Laser), Florianópolis, Brazil (BRA).
    Weingaertner, Walter Lindolfo
    Federal University of Santa Catarina, Department of Mechanical Engineering, Laboratory of Precision Engineering, Laser Division (LMP-Laser), Florianópolis, Brazil (BRA).
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Federal University of Uberlandia, Center for Research and Development of Welding Processes (Laprosolda), Uberlândia Brazil (BRA).
    Souza, Tiago
    Federal University of Santa Catarina, Department of Mechanical Engineering, Laboratory of Precision Engineering, Laser Division (LMP-Laser), Florianópolis, Brazil (BRA).
    Comparison of methods to correlate input parameters with depth of penetration in LASER welding2019Inngår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 101, nr 5-8, s. 1157-1169Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Despite the industrial relevance of LASER welding, determination of sustainable parameterization is still a challenge. Trial and error, or even not totally justified methodologies, are frequently applied on LASER welding parametrization. This approach potentially leads to a decrease of the process tolerance and, consequently, increasing the likelihood of imperfections, which means extra operational time and raising of the final cost. The present paper addresses a comparative discussion about five factors experimentally determined and frequently used to predict depth of penetration in LASER welding. The experiments were performed with a 10-kW fiber LASER. In a first batch, power was varied while welding speed was fixed at 1 m/min. In a second batch, welding speed was varied and power was kept at 10 kW. The first demonstrated concern on using these popular factors is the definition and quantification of LASER energy. For evidencing this aspect, two samples were processed with the same welding energy of 120 kJ/m, yet resulting in completely different penetrations. Eventually, an empirical model based on power as a factor allowed a more reliable prediction of the depth of penetration.

  • 8.
    dos Santos Paes, Luiz Eduardo
    et al.
    Federal University of Uberlândia, Faculty of Mechanical Engineering, Center for Research and Development of Welding Processes, Uberlândia, Minas Gerais, (BRA).
    Pereira, Milton
    Federal University of Santa Catarina, Department of Mechanical Engineering, Precision Engineering Laboratory, Laser Division, Florianópolis, Santa Catarina, (BRA).
    Xavier, Fábio Antônio
    Federal University of Santa Catarina, Department of Mechanical Engineering, Precision Engineering Laboratory, Laser Division, Florianópolis, Santa Catarina, (BRA).
    Weingaertner, Walter Lindolfo
    Federal University of Santa Catarina, Department of Mechanical Engineering, Precision Engineering Laboratory, Laser Division, Florianópolis, Santa Catarina, (BRA).
    D’Oliveira, Ana Sofia Clímaco Monteiro
    Federal University of Paraná, Department of Mechanical Engineering, Additive Manufacturing and Surface Engineering Laboratory, Curitiba, Paraná, (BRA).
    Costa, Erick Cardoso
    Federal University of Santa Catarina, Department of Mechanical Engineering, Precision Engineering Laboratory, Laser Division, Florianópolis, Santa Catarina, (BRA).
    Vilarinho, Louriel Oliveira
    Federal University of Uberlândia, Faculty of Mechanical Engineering, Center for Research and Development of Welding Processes, Uberlândia, Minas Gerais, (BRA).
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Federal University of Uberlândia, Faculty of Mechanical Engineering, Center for Research and Development of Welding Processes, Uberlândia, Minas Gerais, (BRA); Federal University of Paraná, Department of Mechanical Engineering, Additive Manufacturing and Surface Engineering Laboratory, Curitiba, Paraná, (BRA).
    Understanding the behavior of laser surface remelting after directed energy deposition additive manufacturing through comparing the use of iron and Inconel powders2021Inngår i: Journal of Manufacturing Processes, ISSN 1526-6125, Vol. 70, s. 494-507Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Laser directed energy deposition with powder (pDED-L) is one of the most popular techniques for additive manufacturing. However, for some applications, the resulting surface finish requires post-processing machining. Laser remelting processing has been cited as a means of decreasing machining needs in other applications. The objective of this study was to assess the performance and gain a better physical understanding of the laser remelting process as an alternative to the conventional post-processing techniques applied after pDED-L. pDED-L and remelting were performed using a 10 kW fiber laser source and iron and Inconel 625 powders as feedstock to compare the surface roughness and waviness under different processing conditions (three heat input levels). Through 2D and 3D surface measurements, as well as scanning electron microscopy (SEM), surface features were qualified and quantified. SEM and optical microscopy (OM) were also employed for metallurgical characterization of the roughness. The surface micro-notch effect was assessed through the stress concentration factor (kt). The results indicated attenuation of the average roughness (Ra) by around 30% for iron and 70% for Inconel when laser remelting was employed. In addition, kt presented a 31% reduction for iron and 29% reduction for Inconel. The performance varied according to the type of material used and was mainly related to differences in thermal diffusivity and electrical resistivity. It was concluded that laser remelting is a promising technology for coupling with pDED-L aimed at producing 3D metal components with superior quality while allowing a faster production rate in comparison to current practices.  

  • 9.
    Ferreira, Guilherme Rezende Bessa
    et al.
    Faculty of Engineering, Federal University of Juiz de Fora, Juiz de Fora.
    Filho, Roberto Malheiros Moreira
    Faculty of Engineering, Federal University of Juiz de Fora, Juiz de Fora (BRA).
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Laprosolda, Center for Research and Development of Welding Processes, Federal University of Uberlandia, Uberlandia, Minas Gerais (BRA).
    Lagares, Moisés Luiz Jr.
    Faculty of Engineering, Federal University of Juiz de Fora, Juiz de Fora (BRA).
    Exploring a locus of maximum metal transfer stability of the short-circuiting GMAW process based on the reignition voltage peaks2021Inngår i: Journal of the Brazilian Society of Mechanical Sciences and Engineering, ISSN 1678-5878, E-ISSN 1806-3691, Vol. 43, nr 11Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The welding process stability is a critical factor regarding the quality of the manufactured products in the Industry. There are two approaches to assess the metal transfer stability based on droplet transfer period: scanning arc voltage or scanning wire feed speed. Studies based on each of the approaches can be found in current literature, but there are no reported studies evaluating the role of the arc reignition voltage peak (RiVP) on stability. Thus, this paper aimed to propose a novel method to assess the short-circuiting gas metal arc welding metal transfer stability based on arc reignition voltage peak distribution, via wire feed speed scanning route, and compare the effectiveness of the proposed method to the existing ones. First, the authors depicted the fundamentals of the ideal metal transfer (the most stable). A novel stability index based on the RiVP distribution was introduced. The results showed that the methodology was capable of defining a locus of maximum metal transfer stability through the arc RiVP regularity. It also demonstrated that, in a regular short-circuiting transfer mode, the RiVP obeys an expected distribution. Besides, the most regular arc reignition-related quantity was directly related to the most regular period-related characteristic. After validating the methodology, the proposed method was demonstrated to be, potentially, a novel manner to assess and seek the maximum stability of the short-circuiting gas metal arc welding process.

  • 10.
    Ferreira, Rafael Pereira
    et al.
    Federal Institute of Education, Science and Technology of Maranhão (IFMA), Campus Barra do Corda, Barra do Corda (BRA); Center for Research and Development of Welding Processes (Laprosolda), Federal University of Uberlândia (UFU), Uberlândia (BRA).
    Vilarinho, Louriel Oliviera
    Center for Research and Development of Welding Processes (Laprosolda), Federal University of Uberlândia (UFU), Uberlândia (BRA).
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Center for Research and Development of Welding Processes (Laprosolda), Federal University of Uberlândia (UFU), Uberlândia (BRA).
    Development and implementation of a software for wire arc additive manufacturing preprocessing planning: trajectory planning and machine code generation2022Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To overcome a shortage of flexible and low-cost solutions for wire arc additive manufacturing (WAAM) preprocessing, this work´s objective was to develop and validate an in-house computational programme in an open-source environment for WAAM preprocessing planning. Algorithms for reading STL (stereolithography) files and implementing rotation, slicing, trajectory planning, and machine code generation were elaborated and implemented in the Scilab environment (free and open-source). A graphical interface was developed to facilitate user interaction, with 5 options for path planning. The functionality of each work step is detailed. For validation of the software, single and multiple-layer prints, with different geometrical complexity and printing challenges, were built in a CNC table geared by the generated machine code. The validation criteria were deposition imperfection, morphological, and dimensional tolerances. The outputs showed that the parts were successfully printed. Therefore, this work demonstrates that Scilab provides the necessary resources for companies and universities to implement and/or develop algorithms for planning and generating trajectories for WAAM. Moreover, emerging ideas can be reasonably easily implemented in such software, not always possible in commercial packages. 

    Fulltekst (pdf)
    Springer
  • 11.
    Hurtig, Kjell
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Choquet, Isabelle
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Svensson, Lars-Erik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    A critical analysis of weld heat input measurement through a water-cooled stationary anode calorimeter2015Inngår i: Proceedings of JOM 18 International conference on joining materials, Helsingör, Danmark, april 26-29, 2015, JOM-institute , 2015, s. 1-19Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A comprehensive model on heat transfer in welded plates is able to calculate the amount of heat losses from the surfaces. A model demands as input parameter the amount of heat delivered to the plate, independently of any loss (called here gross heat input for clarity). However, the great discrepancies among the results of calorimetric measurements have left many researchers skeptical about using this parameter in modeling as absolute term. The objective of this work was to assess the use of a water-cooled stationary anode calorimeter to obtain not only arc efficiency, but also gross heat input. A series of tests was carried out to determine the effect of current, material type and water flow rate on the calorimeter performance, as well as to evaluate some measures for reducing the calorimeter intrinsic errors. Finally, a sensitivity test was conducted to estimate the effect of measurement inaccuracies on the absorbed heat and arc efficiency values. The results showed that this calorimetric approach is a simple way for measuring gross heat inputs in arc welding. Nevertheless some improvement to reduce heat losses from the top surface and boost heat sinking from the opposite surface of the test coupon must be applied. This calorimeter is, on the other hand, highly sensitive to the parameter measurements, leading to errors up to ± 0.09 in arc efficiency determination if the instrument is not properly calibrated and installed.

  • 12.
    Hurtig, Kjell
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Choquet, Isabelle
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap, Avd för maskinteknik.
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Svensson, Lars-Erik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    A critical analysis of weld heat input measurement through a water-cooled stationary anode calorimeter2016Inngår i: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, Vol. 21, nr 5, s. 339-350Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Comprehensive models of heat transfer require specification of the total amount of heat received by the workpiece. The objective of this work was to critically examine the use of a water-cooled stationary anode calorimeter to obtain both arc efficiency and total heat input into the workpiece. For simplicity and clarity, this last quantity is called the gross heat input. The effects of current, material type and water flow rate on the calorimeter performance were determined experimentally. Some measures for reducing errors in calorimetry were evaluated. Improvements were made to reduce heat losses from the top surface of the test coupon and boost heat removal from the opposite surface. A sensitivity test was conducted to estimate the effect of measurement inaccuracies. The results demonstrate the effectiveness of calorimetry for measuring gross heat input in arc welding.

  • 13.
    Högström, Mats
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Fadaei, Amirhosein
    Högskolan Väst, Institutionen för ingenjörsvetenskap.
    Rahimi, Amin
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Li, Peigang
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Igestrand, Mattias
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Proposal and Assessment of a Multiple Cycle-Continuous Cooling Transformation (MC-CCT) Diagram for Wire Arc Additive Manufacturing of Thin Walls2023Inngår i: Metals, ISSN 2075-4701, Vol. 13, nr 9, artikkel-id 1533Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Continuous cooling transformation (CCT) diagrams of base metals are common in welding. They can be built using physical or numerical simulations, each with advantages and limitations. However, those are not usual for weld metal, considering its variable composition due to the dilution of the weld into the base metal. Wire Arc Additive Manufacturing (WAAM) is a distinctive casein which the interest in materials comparable with weld composition raises attention to estimating their mechanical properties. Notwithstanding, this concept is still not used in WAAM. Therefore, the aim of this work was to address a methodology to raise MC-CCT (Multiple Cycle ContinuousCooling Transformation) diagrams for WAAM by combining physical and numerical simulations. A high-strength low-alloy steel (HSLA) feedstock (a combination of a wire and a shielding gas) was used as a case study. To keep CCT as representative as possible, the typical multiple thermal cycles for additive manufacturing thin walls were determined and replicated in physical simulations (Gleeble dilatometry). The start and end transformations were determined by the differential linear variation approach for each thermal cycle. Microstructure analyses and hardness were used to characterise the product after the multiple cycles. The same CCT diagram was raised by a commercial numerical simulation package to determine the shape of the transformation curves. A range of austenitic grain sizes was scanned for the curve position matching the experimental results. Combining the experimental data and numerically simulated curves made estimating the final CCT diagram possible.

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  • 14.
    Jorge, Vinicius Lemes
    et al.
    Universidade Federal de Uberlândia – UFU, Centro para Pesquisa e Desenvolvimento de Processos de Soldagem – Laprosolda, Uberlândia, MG, Brasil.
    Alves Santos, Cesar Henrique
    Universidade Federal de Uberlândia – UFU, Centro para Pesquisa e Desenvolvimento de Processos de Soldagem – Laprosolda, Uberlândia, MG, Brasil.
    Scotti, Fernando Matos
    Universidade Federal de Uberlândia – UFU, Centro para Pesquisa e Desenvolvimento de Processos de Soldagem – Laprosolda, Uberlândia, MG, Brasil.
    Larquer, Thiago Resende
    Universidade Federal de Uberlândia – UFU, Centro para Pesquisa e Desenvolvimento de Processos de Soldagem – Laprosolda, Uberlândia, MG, Brasil.
    Mota, Carolina Pimenta
    Instituto Federal de Educação, Ciência e Tecnologia do Triângulo Mineiro – IFTM, Patos de Minas, MG, Brasil.
    Reis, Ruham Pablo
    Universidade Federal de Uberlândia – UFU, Centro para Pesquisa e Desenvolvimento de Processos de Soldagem – Laprosolda, Uberlândia, MG, Brasil.
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Universidade Federal de Uberlândia – UFU, Centro para Pesquisa e Desenvolvimento de Processos de Soldagem – Laprosolda, Uberlândia, MG, Brasil.
    Development and Evaluation of Wire Feeding Pulsing Techniques for Arc Welding: Desenvolvimento e Avaliação de Técnicas para Pulsação da Alimentação de Arame em Soldagem a Arco2018Inngår i: Soldagem & Inspeção, ISSN 0104-9224, E-ISSN 1980-6973, Vol. 23, nr 3, s. 326-339Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Applying pulsed wire feeding techniques is one of the new approaches for welding, such as for GTAW and GMAW. However, these techniques invariably require specific feeders and/or welding torches, limiting its implementation due to the high costs of the equipment. Thus, the current work aims to introduce and exploratorily evaluate techniques to pulse the wire feeding that works independently from the feeder and/or torch. The first technique is electromechanically driven, and the second one based on electromagnetics. The effects of amplitude and frequency of the pulsed feeding were evaluated in terms of weld bead formation over plates and of the corresponding electric signals. For GTAW, the pulsed wire feeding is capable of modifying the weld bead and make the metal transfer from the wire to the pool more regular. For GMAW, it was found that the pulsing of the wire feeding can interfere with the process, being capable of turning an irregular globular metal transfer into a regular one, while decreasing the mean current and affecting the bead formation. Overall, it is concluded that pulsed wire feeding can affect the processes, even when made independently from the feeder and torch, opening a field for development of derivative welding technologies.

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  • 15.
    Jorge, Vinicius Lemes
    et al.
    University of Uberlandia, Center for Research and Development of Welding Processes of the Federal, Uberlandia, Brazil.
    Gohrs, Raul
    IMC Soldagem, Palhoça, Brazil.
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Active power measurement in arc welding and its role in heat transfer to the plate2017Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 61, nr 4, s. 847-856Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A contemporary paper claimed that a method using the resistance of impedance (active power) for arc power calculation is more accurate than the conventional approach, with consequences on the actual heat transfer to the plate. However, despite the comprehensive reasoning, no heat-related results are shown in this intriguing paper to support the claim. Thus, the aim of this work was to apply the proposed method for determining the weight of active power in the total arc power. A series of weldments was carried out, by using GTAW in constant and pulsed current modes and short-circuiting GMAW with different inductance settings. The effect of the active power on the heat transfers to the plate was assessed by both bead cross-section geometries and calorimetry. The results showed that even a significant fraction of active power of the total power was reached, no changes in bead geometry or heat input were found. A review of the assumptions used in the primal paper showed that an arc is better represented by an ER circuit than by an RLC circuit. As a conclusion, the arc as a reactance-free load presents no component such as non-active power and the conventional approaches are accurate methods to measure arc power, representing the actual active power. © 2017, The Author(s).

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  • 16.
    Jorge, Vinicius Lemes
    et al.
    Federal University of Uberlandia (UFU), Center for Research and Development of Welding Processes (Laprosolda), Uberlândia, MG, Brazil (BRA).
    Scotti, Fernando Matos
    Federal University of Uberlandia (UFU), Center for Research and Development of Welding Processes (Laprosolda),Uberlândia, MG, Brazil (BRA).
    Reis, Ruham Pablo
    Federal University of Uberlandia (UFU), Center for Research and Development of Welding Processes (Laprosolda),Uberlândia, MG, Brazil (BRA).
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Federal University of Uberlandia (UFU), Center for Research and Development of Welding Processes (Laprosolda),Uberlândia, MG, Brazil (BRA); Federal University of Parana (UFPR), Graduate Program in Materials Science and Engineering, Curitiba, PR, Brazil (BRA).
    The potential of wire feed pulsation to influence factors that govern weld penetration in GMA welding2020Inngår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 110, s. 2685-2701Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Derivative welding processes are in many cases capable of altering phenomena that determine fundamental aspects of weld bead formation. Some of these evolutions act over the wire feed dynamics. However, in this scenario, the effects of the wire feed pulsation on the weld bead formation governing factors have not been fully explored yet. Therefore, this work aimed at examining how a wire feed pulsation approach affects the droplet transfer in gas metal arc welding and how its interaction with the molten pool defines the weld bead penetration. Bead-on-plate weldments were produced by varying the wire feed pulsation frequency, yet keeping the same levels of arc energy and wire feed speed, with the power source operating in constant voltage and current modes. To assess the droplet transfer behavior, high-speed imaging was used. The geometry of the weld beads was compared in terms of fusion penetration. The results showed that an increase in the wire feed pulsation frequency intensifies the detachment frequency of the droplets, being possible to accomplish a stable metal transfer with them straightly projected toward the weld pool, which contributed to a centralized-increased penetration profile. Based on a descriptive model, it was demonstrated that the increase in droplet momentum or kinetic energy, due to the wire feed pulsation, was not enough to justify the penetration enhancement. It was concluded that the wire feed dynamics can also stimulate surface tension variations in the weld pool and therefore disrupt the behavior of its mass and heat convection, supporting fusion penetration.

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  • 17.
    Jorge, Vinicius Lemes
    et al.
    Federal University of Uberlandia (UFU), Center for Research (BRA)and Development of Welding Processes (Laprosolda), Uberlândia, MG .
    Scotti, Fernando Matos
    Federal University of Uberlandia (UFU), Center for Research and Development of Welding Processes (Laprosolda), Uberlândia, MG (BRA).
    Reis, Ruham Pablo
    Federal University of Uberlandia (UFU), Center for Research and Development of Welding Processes (Laprosolda), Uberlândia, MG (BRA).
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Federal University of Uberlandia (UFU), Center for Research and Development of Welding Processes (Laprosolda), Uberlândia, MG (BRA), Federal University of Parana (UFPR), Graduate Program in Materials Science and Engineering, Curitiba, PR, (BRA).
    Wire feed pulsation as a means of inducing surface tension metal transfer in Gas Metal Arc Welding2021Inngår i: JOURNAL OF MANUFACTURING PROCESSES, ISSN 1526-6125, Vol. 62, s. 655-669Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Gas Metal Arc Welding (GMAW) derivative processes have gained attention due to their capacity to perform specific functions, such as reducing spattering during short-circuiting. However, the short-circuiting transfer nature allows devising other features, such as to work with low current yet with high voltage. Although this arrangement is typical of globular transfer when applied in GMAW, the assistance of wire feed pulsation by itself could make the use of this combination doable. Therefore, this work aimed at exploring the technical feasibility of short-circuiting GMAW with higher voltage level with the aid of a wire feed pulsation technique, rather than relying on current waveform control strategies. In this case, a home-developed device that superimposes a pulsation linear movement to the wire over its continuous movement was employed. To prove the concept, wire pulsation and long arc length during arcing were applied in experiments with the power source operating either in constant voltage or constant current modes. In order to quantify and validate the approach, a range of pulsation frequencies was explored and compared with conditions with continuous feeding. The metal transfer regularity was evaluated following the Laprosolda Metal Transfer Regularity Criterion, and geometric parameters of the weld beads were compared as complement. To assess the metallic transfer behavior, high-speed imaging was also used. A reasoning in terms of arc length was successfully applied to different conditions based on the melting rate equation and misleading voltage usage in short-circuiting for this purpose was demonstrated. The results showed that the wire feed pulsation approach is adequate to improve metal transfer regularity in shortcircuiting GMAW, as long as the power source is set to operate in current constant mode. Furthermore, the actual arc length plays a significant role in the wire feed pulsation process performance.

  • 18.
    Jorge, Vinicius Lemes
    et al.
    Center for Research and Development of Welding Processes (Laprosolda), Federal University of Uberlandia (UFU), Uberlândia (BRA).
    Teixeira, Felipe Ribeiro
    Center for Research and Development of Welding Processes (Laprosolda), Federal University of Uberlandia (UFU), Uberlândia (BRA).
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Center for Research and Development of Welding Processes (Laprosolda), Federal University of Uberlandia (UFU), Uberlândia (BRA).
    Pyrometrical Interlayer Temperature Measurement in WAAM of Thin Wall: Strategies, Limitations and Functionality2022Inngår i: Metals, ISSN 2075-4701, Vol. 12, nr 5, s. 1-17Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Significant efforts have been spent determining or monitoring interlayer temperatures (IT) to increase quality in Wire Arc Additive Manufacturing (WAAM). However, an uneven thermal profile in the wall and a temperature gradient along the layer length are expected after a thin wall layer deposition, questioning the effectiveness of IT and its measuring approaches. After identifying the holistic meaning of IT, this work aimed at confronting two strategies using infrared pyrometers, elucidating their advantages and limitations for both open and closed‐loop control. The proposed Upper and Sideward Pyrometer strategies were presented in detail and then assessed at different distances from the heat source. A calibration procedure was proposed. The results confirmed the existence of a natural temperature gradient along the wall. In addition, they showed how differently the arc heat affects the measured points (in intensity and steadiness) according to the strategy. Therefore, the interlayer temperature measured at a specific point on a part manufactured by WAAM should be taken as a reference and not an absolute value; the absolute value changes according to the measuring approach, sensor positioning and calibration. Using a temperature reference, both strategies can be used in open‐loop control to reach repeatability (geometrical and metallurgical) between layers. However, the Sideward Pyrometer strategy is more recommended for feedback control of production, despite being less flexible. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

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  • 19.
    Jorge, Vinicius Lemes
    et al.
    Federal University of Uberlandia, Center for Research and Development of Welding Processes, Uberlandia (BRA).
    Teixeira, Felipe Ribeiro
    Federal University of Uberlandia, Center for Research and Development of Welding Processes, Uberlandia (BRA).
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Federal University of Uberlandia, Center for Research and Development of Welding Processes, Uberlandia (BRA).
    Scotti, Fernando Matos
    Linde GmbH, Linde Technologies, Department of Arc Technologies, Unterschleißheim (DEU).
    Siewert, Erwan
    Linde GmbH, Linde Technologies, Department of Arc Technologies, Unterschleißheim (DEU).
    The significance of supplementary shielding in WAAM of aluminium thin walls2023Inngår i: Journal of Manufacturing Processes, ISSN 1526-6125, Vol. 106, s. 520-536Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    WAAM (wire arc additive manufacturing) of aluminium requires special operational care to avoid problems such as instabilities, contamination or porosities. This work aims at verifying whether supplementary shielding gas can affect the WAAM performance when building Al alloy thin walls, in terms of metal transfer, porosity, superficial finishing, and geometrical and metallurgical features. Thin walls were manufactured with and without supplementary shielding (ultra-pure Ar). A dedicated nozzle was designed in-house to provide additional protection against the reaction with surrounding atmospheric gases. Pure Ar and two Ar-based commercial shielding gases with different additives were employed to make the conclusions more sustainable. It was possible to conclude that supplementary shielding leads to better metal transfer regularity, cleaner lateral and surface, a shinier top layer appearance, and a slight trend to higher microhardness. On the other hand, it does not affect porosity after layer depositions, wall geometry (the total and effective layer width, layer height, and surface waviness of the walls), and microstructures. Finally, regarding the performance of shielding gases, there is no evidence of any effect from the supplementary shielding, since this approach improved the process operationality with the three different shielding gases but did not change their individual tendencies. 

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  • 20.
    Jorge, Vinius Lemes
    et al.
    Federal University of Uberlandia, Uberlândia, MG, Brazil (BRA).
    Scotti, Fernando Matos
    Federal University of Uberlandia, Uberlândia, MG, Brazil (BRA).
    Reis, Ruham Pablo
    Federal University of Uberlandia, Uberlândia, MG, Brazil (BRA).
    Scotti, Américo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    The effect of pulsed cold-wire feeding on the performanceof spray GMAW2020Inngår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 107, s. 3485-3498Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The application of pulsed cold-wire (P-CW) feeding has been one of the new approaches for arc welding over the past years. Such technique applied to GTAW shows that it can influence the process performance. However, P-CW feeding in GMAW has not been explored yet. Thus, the current work aimed at introducing and evaluating the effects of P-CW on the performance of GMAW, particularly with the spray metal transfer. The P-CW pulsing frequency and the angle between the cold-wire and the plate were varied in bead-on-plate and V-groove weldments. The effects of the P-CW on the weld bead geometry and metallurgical texture were, then, examined through cross-sections. The metal transfer from the wire tip to the weld pool and the arc behavior during wire feeding were analyzed backed by high-speed imaging. A thermal camera was used to monitor the back of the plates to examine the heat behavior with both the P-CW and non-pulsed feeding conditions. On the one hand, the results revealed that, although the pulsation affects the arc and the electric signal behavior and the metal transfer, no sensitive influence could be noticed regarding the weld bead geometries. On the other hand, the pulsed cold-wire feeding interfered in the thermal profile outside the weld pool. For the highest frequency explored, regardless the feeding angle, less heat was transferred to the plate. The smaller heat input in these cases limited grain growth, reducing the coarse grain HAZ area and resulting in a more refined microstructure. Therefore, P-CW showed to interfere in the GMAW process performance.

  • 21.
    Li, Peigang
    et al.
    ESAB AB, Gothenburg, Sweden.
    Hurtig, Kjell
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Högström, Mats
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Svensson, Lars-Erik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    A contribution to the study of negative polarity in GMA welding2018Inngår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 95, nr 5-8, s. 2543-2553Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    GMAW using the electrode with negative polarity (DCEN) has been frequently suggested as a potential means of increasing production capacity. The objective of this work was to further study the performance of negative polarity in GMAW of carbon steels. In this project phase, bead-on-plate welds were carried out in flat position to assess the effect of different potential shielding gas compositions on bead geometry, finishing and spattering. The characteristics were compared with DCEP at the same current, but depositing the same volume of material per unit of length (more industrial related comparison). The arc length was kept the same by adjusting voltage to reach shortest arcs, yet with suitable non short-circuiting metal transfer mode. An approach to measure bead convexity was also proposed and assessed. The results showed that DCEN is feasible as a means of increasing GMAW production capacity. However, to become DCEN applicable with GMAW, the results suggest an Ar based blend with around 6.5 % of O2 is the most appropriate shielding gas, as much as that there is a demand for a standard electronic controlled power source able to work in constant current mode. 

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  • 22.
    Lippold, John C.
    et al.
    Welding Engineering Program, Department of Materials Science and Engineering, Ohio State University, Columbus, OH, (USA).
    Bollinghaus, Ing Thomas
    Department of Component Safety (Dpt.9), Bundesanstalt für Materialforschung und –prüfung, Berlin, (DEU).
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Welding in the world-update 20212021Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 65, nr 2, s. 167-169Artikkel i tidsskrift (Annet vitenskapelig)
  • 23.
    Liskevych, Olga
    et al.
    Center for Research and Development of Welding Processes of Federal University of Uberlandia (Laprosolda), Brazil.
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Influence of the CO2 Content on Operational Performance of Short-Circuit GMAW2015Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 59, nr 2, s. 217-224Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    CO2 blended with Ar is the most common shielding gas used for short-circuit GMAW. There has been some technical knowledge devised from the process application over the years (personal opinion and results from practice) on the selection of the gas blend composition. However, there is still lack of more scientific data to explain the performance of the mixtures. This paper presents a systematic study of the influence that CO2 content in mixture with Argon has on the operational performance of the short-circuit GMAW. The objective of this study was to describe, to quantify and to explain the alterations in the metal transfer behavior, spatter generation, weld bead geometry and bead finish due to the different CO2 contents in the shielding gas. Carbon steel plates were welded in adequate parametric conditions for each CO2+Ar shielding gas composition (CO2 ranging from 2% to 100%). These parametric conditions were found by applying a metal transfer regularity index over welds carried out at different voltage settings for each gas blend. A target of 130 A was applied as base for comparison. Laser shadowgraphy with high speed filming and current and voltage oscillograms were used as analysis tools. The results showed (and confirmed) that the increase of the CO2 content deteriorates metal transfer regularity, leading to excessive spatter generation and uneven bead appearance, but increases the penetration and the fusion area of the weld beads and improves bead convexity. In general, the CO2 content should neither be lower than 10% (unless for thin plates) nor higher than 30%.

  • 24.
    Mishchenko, Andrii
    et al.
    Universidade Federal de Uberlândia – UFU, Grupo Centro para Pesquisa e Desenvolvimento de Processo de Soldagem – Laprosolda, Uberlândia, MG, Brasil.
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Universidade Federal de Uberlândia – UFU, Grupo Centro para Pesquisa e Desenvolvimento de Processo de Soldagem – Laprosolda, Uberlândia, MG, Brasil.
    Residual Stresses in Arc Welding: A Holistic Vision2018Inngår i: Soldagem & Inspeção, ISSN 0104-9224, E-ISSN 1980-6973, Vol. 23, nr 1, s. 93-112Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    There are several examples in current literature where assumptions regarding residual stresses are made, yet rarely confirmed in practice. To validate this statement, this work presents a critical view on the subject through a bibliographic review. A series of conflicting results were found when researchers attempted, both experimentally and by simulation, to define, quantify, or even qualify, the individual effect of each factor on residual stress generation. It was concluded that the reason for this would be the lack of a holistic view to study the subject. Therefore, a diagram is proposed, which lists and classifies as primary and secondary the governing factors related to the generation of residual stresses, to facilitate the understanding of the effect of each factor. It was also observed a lack of harmonization in publications, both in symbology and in terminology, of the residual stress axes and components. Therefore, a symbology and terminology proposal, with the intention of facilitating the comprehension and transportability of results, is presented. Eventually, from this work is therefore expected a better understanding of the reasons for the literature assumptions to be not always confirmed in practice.

  • 25.
    Mishchenko, Andrii
    et al.
    Federal University of Uberlandia (UFU), Laprosolda-Center for Research and Development of Welding Processes, Uberlândia, MG, Brazil.
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Federal University of Parana (UFPR), Graduate Program in Materials Science and Engineering, Curitiba, PR, Brazil.
    Welding thermal stress diagrams as a means of assessing material proneness to residual stresses2021Inngår i: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 56, nr 2, s. 1694-1712Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, the proposal and appraisal of a method to describe in a quantitative manner the phenomenon of thermal stresses formation in welding at different heat-affected zone (HAZ) regions and under different cooling rates, by means of physical simulation, are explained. Under the denomination of welding thermal stress diagrams (WTSD), initially the concept and experimental arrangements needed to use the idea, based on a Gleeble simulator, are revealed. An approach to determine more realistic thermal cycles (peak temperature and heating/cooling rates) is introduced and applied. The method assessment was carried out by using specimens of a HSLA quenchable steel subjected to different cooling rates (covering a wide range of typical welding heat inputs) and peak temperatures (representing regions progressively farther away from the fusion line). The different thermal stress (TS) curves proved the concept based on the justification of the results. In addition, it was physically demonstrated that TS curves are governed mainly by two complex concurrent phenomena, namely contraction under restriction of heated areas and the expansibility of phase transformation. It was concluded that due to this balance, the highest residual stress (RS) does not occur either at slowest cooling rate or at fastest cooling rate. Nevertheless, the highest RS may not occur at the coarse grain zone either. TS progressively drops along the HAZ regions away from critical regions, and even at sub-critical regions there is tensile RS. Complementarily, it was also concluded that WTSD by physical simulation allows one to determine the deformation behaviour of a material as a function of temperature. This information can be used as input or calibration in modelling for thermal stress generation in steels.

  • 26.
    Mishchenko, Andrii
    et al.
    Federal University of Uberlandia (UFU),Laprosolda-Center for Research and Development of Welding Processes, Uberlândia, Brazil.
    Wu, Leonardo
    Brazilian Nanotechnology National Laboratory (LNNano), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil.
    da Silva, Vanessa K.
    Brazilian Nanotechnology National Laboratory (LNNano), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil.
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Federal University of Uberlandia (UFU),Laprosolda-Center for Research and Development of Welding Processes, Uberlândia, Brazil.
    Analysis of residual stresses resulting from the surface preparation for X-ray diffraction measurement2018Inngår i: Journal of the Brazilian Society of Mechanical Sciences and Engineering, ISSN 1678-5878, E-ISSN 1806-3691, Vol. 40, nr 2, artikkel-id 94Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    There is no consensus in the literature on the need to remove preprocessing layers from the material prior to the measurement of residual stresses by X-ray diffractometer. Thus, the purpose of this work was to evaluate the residual stresses induced by material preprocessing and its evolution during the preparation of the surface by electrolytic removal. Sample surfaces were pre-processed by grinding and sandblasting and the resulting residual stresses were measured by X-ray diffractometry. At each removal stage, the evolution of residual stresses, hardness and microstructure of the surface were verified. It was concluded that different preprocessing methods can induce surface residual stresses of either tension or compression, reaching different depths. Removal by electrolytic method of the modified layer has shown itself capable of reducing significantly the magnitude of the residual stresses induced by preprocessing. On the other hand, the depth of deformed grains or surface hardness proved to be incapable of predicting the depth of induced residual stresses. Finally, it was discussed whether or not the layers removed by this method reveal the subsurface stresses and if the removal should take place before or after a second processing.

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  • 27.
    Pablo Reis, Ruham
    et al.
    Universidade Federal de Uberlândia—UFU, Centro Para Pesquisa e Desenvolvimento de Processos de Soldagem—LAPROSOLDA, Uberlândia, Brazil.
    Skhabovskyi, Iaroslav
    Universidade Federal de Uberlândia—UFU, Centro Para Pesquisa e Desenvolvimento de Processos de Soldagem—LAPROSOLDA, Uberlândia, Brazil.
    Lima Santos, Alberto
    Universidade Estadual Paulista—UNESP, Departamento de Tecnologias e Materiais, Guaratinguetá, Brazil.
    Sanches, Leonardo
    Universidade Federal de Uberlândia—UFU, Centro Para Pesquisa e Desenvolvimento de Processos de Soldagem—LAPROSOLDA, Uberlândia, Brazil.
    Cocchieri Botelho, Edson
    Universidade Estadual Paulista—UNESP, Departamento de Tecnologias e Materiais, Guaratinguetá, Brazil.
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Universidade Federal de Uberlândia—UFU, Centro Para Pesquisa e Desenvolvimento de Processos de Soldagem—LAPROSOLDA, Uberlândia, Brazil.
    Fiber-metal laminate panels reinforced with metal pins2018Inngår i: Optimum Composite Structures / [ed] Maalawi. Karam, London: IntechOpen , 2018, s. 93-120Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    Fiber-metal laminates (FMLs) are key to modern composite structures and metal-compositecoupling is crucial to improve their effectiveness. Cold-metal transfer (CMT) PIN welding,in correlated efforts, has been successfully explored as a metal-composite hybrid joiningapproach. This work proposes a novel development on FMLs, which consists of introducingmetal pins welded by CMT PIN for anchoring their metal and composite layers together.Thus, miniaturized FML panels with different pin deposition spacing and patterns are evaluatedwith emphasis in drop-weight testing followed by buckling and by means of Iosipescushear test as complement. They are also subjected to cosmetic and preliminary modal analyses.Besides not adding significant weight, the pins does not make the panels more brittleand their distribution does not imply significant effect in the capacity that the panels have todissipate impact. The panels with pins exhibit a less catastrophic trend, indicating damagetolerance improvement as significantly higher loads at longer axial displacements in bucklingtest after impact are achieved. The anchoring effect of the pins is confirmed throughoutthe shear test results. The pins also significantly increase the damping factor of the panelsand the changes in their metal surfaces by the CMT PIN process are considered as irrelevant.

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  • 28.
    Pereira Ferreira, Rafael
    et al.
    Federal Institute of Maranhão, Department of Mechanic, Barra do Corda (BRA) ; Federal University of Uberlandia, Uberlândia ( BRA).
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Federal University of Uberlandia, Center for Research and Development of Welding Processes, Uberlândia (BRA).
    Concept of a Novel Path Planning Strategy for Wire + Arc Additive Manufacturing of Bulky Parts : Pixel2021Inngår i: Metals, E-ISSN 2075-4701, Vol. 11, nr 3, s. 1-20, artikkel-id 498Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An innovative trajectory strategy was proposed and accessed for wire arc additive manufacturing (WAAM), applicable to different and more complex geometries, rather than being a single solution. This strategy, named Pixel, can be defined as a complex multitask procedure to carry out optimized path planning, whose operation is made through computational algorithms (heuristics), with accessible computational resources and tolerable computational time. The model layers are fractioned in squared grids, and a set of dots is systematically generated and distributed inside the sliced outlines, resembling pixels on a screen, over which the trajectory is planned. The Pixel strategy was based on creating trajectories from the technique travelling salesman problem (TSP). Unlike existing algorithms, the Pixel strategy uses an adapted greedy randomized adaptive search procedure (GRASP) metaheuristic, aided by four concurrent trajectory planning heuristics, developed by the authors. Interactions provide successive trajectories from randomized initial solutions (global search) and subsequent iterative improvements (local search). After all recurrent loops, a trajectory is defined and written in machine code. Computational evaluation was implemented to demonstrate the effectof each of the heuristics on the final trajectory. An experimental evaluation was eventually carried out using two different not easily printable shapes to demonstrate the practical feasibility of the proposed strategy.

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  • 29.
    Scotti, Americo
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Center for Research and Development of Welding Processes (Laprosolda), Federal University of Uberlandia (UFU), Uberlândia, MG (BRA).
    Batista, Márcio Andrade
    Department of Food Engineering, Federal University of Mato Grosso (UFMT), Cuiabá (BRA).
    Eshagh, Mehdi
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för Matematik, Data- och Lantmäteriteknik.
    Inaccuracy in arc power calculation through a product of voltage and current averages2022Inngår i: Journal of the Brazilian Society of Mechanical Sciences and Engineering, ISSN 1678-5878, E-ISSN 1806-3691, Vol. 44, nr 1, s. 1-9, artikkel-id 11Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    Power is an indirect measurand, determined by processing voltage and current analogue signals through calculations. Using arc welding as a case study, the objective of this work was to bring up subsidies for power calculation. Based on the defnitions of correlation and covariance in statistics, a mathematical demonstration was developed to point out the diference between the product of two averages (e.g. P=UxI) and the average of the products (e.g. P=(UxI). Complementarily, a brief on U and I waveform distortion sources were discussed, emphasising the diference between signal standard deviations and measurement errors. It was demonstrated that the product of two averages is not the same as the average of the products, unless in specifc conditions (when the variables are fully correlated). It was concluded that the statistical correlation can easily fag the interrelation, but if assisted by covariance, these statistics quantify the inaccuracy between approaches. Finally, although the statistics' determination is easy to implement, it is proposed that power should always be calculated as the average of the instantaneous U and I products. It is also proposed that measurement error sources should be observed and mitigated, since they predictably interfere in power calculation accuracy.

  • 30.
    Scotti, Fernando Matos
    et al.
    Federal University of Uberlandia (UFU), Center for Research and Development of Welding Processes (LAPROSOLDA), Uberlândia (BRA).
    da Silva, Leandro João
    Federal University of Uberlandia (UFU), Center for Research and Development of Welding Processes (LAPROSOLDA), Uberlândia (BRA).
    Fernandes, Diandro Bailoni
    Federal University of Uberlandia (UFU), Center for Research and Development of Welding Processes (LAPROSOLDA), Uberlândia (BRA).
    Reis, Ruham Pablo
    Federal University of Uberlandia (UFU), Center for Research and Development of Welding Processes (LAPROSOLDA), Uberlândia (BRA).
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Federal University of Uberlandia (UFU), Center for Research and Development of Welding Processes (LAPROSOLDA), Uberlândia (BRA); Federal University of Parana (UFPR), Graduate Program in Materials Science and Engineering, Curitiba, PR (BRA).
    Effect of O2 content in argon-based shielding gas on arc wandering in WAAM of aluminum thin walls2021Inngår i: CIRP - Journal of Manufacturing Science and Technology, ISSN 1755-5817, E-ISSN 1878-0016, Vol. 32, s. 338-345Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The present work aimed at evaluating the effect of O2 content in argon-based shielding gases over the arc cathodic emission behavior (which can lead to arc wandering) in wire + arc additive manufacturing (WAAM) of thin aluminum walls and its consequences over layer formation. The effect of O2 content on arc wandering was assessed by analyzing cathodic spot behavior through high-speed videography during Gas metal arc (GMA-AM) depositions. Superficial and geometric aspects were analyzed, as well as the sputtering zone width on the wall sides. Through a proposed model, a parallel effect of wire-introduced oxides was weighted to explain arc wandering, searching for oxides in the wall sides (deviating from its action only on the pool). The main finding was that no influence of O2 from the shielding gas was observed on arc wandering, consequently on layer formation, when its content was up to 200 ppm. When an O2 content of 20,000 ppm was employed, oxide searching by the arc in the wall sides was no longer perceived due to enough oxide availability from the shielding gas. However, this favorable condition to layer formation entailed excessive layer oxidation. From the cathodic emission point of view, it can be said that high-purity shielding gases or special mixtures with small additions of O2 (up to 200 ppm) provide no significant advantages for WAAM of aluminum thin walls, at least for the hereby tested alloy and parameters. 

  • 31.
    Scotti, Fernando Matos
    et al.
    Federal University of Uberlandia, Center for Research and Development of Welding Processes, Uberlândia, MG, Brazil (BRA).
    Teixeira, Felipe Ribiero
    Federal University of Uberlandia, Center for Research and Development of Welding Processes, Uberlândia, MG, Brazil (BRA).
    da Silva, Landro Joao
    Federal University of Uberlandia, Center for Research and Development of Welding Processes, Uberlândia, MG, Brazil (BRA).
    de Araújo, Douglas Bezerra
    Federal University of Uberlandia, Center for Research and Development of Welding Processes, Uberlândia, MG, Brazil (BRA).
    Reis, Ruham Pablo
    Federal University of Uberlandia, Center for Research and Development of Welding Processes, Uberlândia, MG, Brazil (BRA).
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Federal University of Uberlandia, Center for Research and Development of Welding Processes, Uberlândia, MG, Brazil (BRA).
    Thermal management in WAAM through the CMT Advanced process and an active cooling technique2020Inngår i: Journal of Manufacturing Processes, ISSN 1526-6125, Vol. 57, s. 23-35Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thermal management is a key factor in wire + arc additive manufacturing (WAAM) in order to mitigate heat accumulation and cope with limitations regarding deposition cycle, geometry issues, and mechanical property anisotropies. From the process point of view, the variable polarity Cold Metal Transfer process, a variant of the Gas Metal Arc (GMA) deposition process named as CMT Advanced, stands out as a prominent option to reduce the heat transferred to the layers under deposition, without dropping the deposition rate. In another front, thermally managing the component by employing a technique called Near Immersion Active Cooling (NIAC) throughout all the deposition time has shown to be a promising tool to remove heat from the part under construction. Thus, the current work proposes an evaluation of the CMT Advanced process combined with the NIAC technique for WAAM. The deposition of Al alloy wall-like preforms was made by varying the positive and negative polarity ratio (EP/EN) in the CMT Advanced process and the layer edge to water distance (LEWD) in the NIAC technique. Comparative runs were made with natural cooling instead of the NIAC technique. Electric signals and porosity were quantified to verify the constancy of the process. Thermal cycles of a fixed point of the walls and some of their geometrical features were measured to see the effect of the EP/EN and LEWD parameters in terms of thermal management performance. For the deposition circumstances applied, minor lack of coalescence between layers and also adjacent discontinuities appeared in the waviness valleys of the walls. Such occurrences justified optical and scanning electron microscopy examinations at these locations as complement analyses. Even so, the results clearly showed that the EP/EN parameter is more influential in the control of the layer dimensions and of the preform surface waviness. The LEWD parameter has more effect on reducing the heat accumulation and, consequently, assuring no wall widening as the number of deposited layers is increased. Finally, it was inferred that the possibility of affecting the thermal cycles and geometries of the resultant preforms with two independent thermal management tools expands the windows for finding optimal deposition parameters in WAAM. © 2020 The Society of Manufacturing Engineers

  • 32.
    Skhabovskyi, Iaroslav
    et al.
    Universidade Federal de Uberlândia (UFU), Laprosolda – Center for Research and Development of Welding Processes, Faculty of Mechanical Engineering, Uberlândia, Brazil.
    Batista, Natassia Lona
    Universidade Estadual Paulista (UNESP), Materials and Technology Department, School of Engineering, Guaratinguetá, Brazil.
    Damato, Cesar Augusto
    ALLTEC Materiais Compostos, São José dos Campos, Brazil.
    Reis, Ruham Pablo
    Universidade Federal de Uberlândia (UFU), Laprosolda – Center for Research and Development of Welding Processes, Faculty of Mechanical Engineering, Uberlândia, Brazil.
    Botelho, Edson Cocchieri
    Universidade Estadual Paulista (UNESP), Materials and Technology Department, School of Engineering, Guaratinguetá, Brazil.
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Laprosolda – Center for Research and Development of Welding Processes, Faculty of Mechanical Engineering, Universidade Federal de Uberlândia (UFU), Uberlândia, Brazil.
    Appraisal of fiber-metal laminate panels reinforced with metal pins deposited by CMT welding2017Inngår i: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 180, nr Supplement C, s. 263-275Artikkel i tidsskrift (Fagfellevurdert)
  • 33.
    Teixeira, Felipe Ribeiro
    et al.
    Federal University of Pará, Department of Mechanical Engineering/PPGEM, 1 Augusto Corrêa St., Guamá, Belém, PA, 66075-110, Brazil.
    Mota, Carlos Alberto Mendes
    Federal University of Pará, Department of Mechanical Engineering/PPGEM, 1 Augusto Corrêa St., Guamá, Belém, PA, 66075-110, Brazil.
    Almeida, Hélio Antônio Lameira
    Federal Institute of Education, Science and Technology of Pará, Mechanics, 1155 Alm. Barroso Ave., Marco, Belém, PA, 66093-020, Brazil.
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Federal University of Uberlandia, Laprosolda (Center for Research and Development of Welding Processes), 2121 João Naves de Ávila Ave., Santa Mônica, Uberlandia, MG, 38400-902, Brazil.
    Operational behavior of the switchback GMAW process using a mechanized rig for arc movement2019Inngår i: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 269, s. 135-149Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Switchback Gas Metal Arc Welding (GMAW) consists of a forward and backward periodic oscillation of the welding torch in the longitudinal direction of the joint. The present work has two objectives, to evaluate the use of a simple and practical device proposed for the switchback manipulation of the torch and to analyze the effect of the switchback parameters on the operational characteristic of the process. Two series of bead-on-plate depositions were planned, using the GMAW process with or without the switchback technique. To find an operational envelope, two levels of equivalent welding speeds were used for covering ranges of oscillation frequency and amplitude. A Ni superalloy was employed as deposition material, aiming at simulating weld overlays. Wire feeding speed, set voltage and contact tip-to-work distance (CTWD) were kept constant. The proposed device was evaluated and proved to be able to make the overlays with all combinations of planned parameters. It was demonstrated that if the backward length (B) is larger than half of the forward's (F), the torch passes more often over the same point of the deposit, and the oftener the torch passes over the same point, the lower the incidence of intermittent narrowing of the bead. By evaluating the surface aspect of the beads, the greater the F, the higher the likelihood of this irregularity. Penetration is shallower with switchback (reason demonstrated based on the fraction of stroke length that the arc is over the subtract), yet the bead surface presents more ripples. Another incident non-geometric conformity is the "dragon back" aspect of the bead, which is favored by faster equivalent welding speeds and high values of forward and backward speeds. The found operational envelope for the GMAW process with switchback was stablished with low-values of speeds and lengths of forward and backward strokes.

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  • 34.
    Teixeira, Felipe Ribeiro
    et al.
    Center for Research and Development of Welding Processes, Federal University of Uberlandia, Uberlândia (BRA).
    Scotti, Fernando Matos
    Center for Research and Development of Welding Processes, Federal University of Uberlandia, Uberlândia, MG, (BRA).
    Jorge, Vinicius Lemes
    Center for Research and Development of Welding Processes, Federal University of Uberlandia, Uberlândia, MG (BRA).
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Center for Research and Development of Welding Processes, Federal University of Uberlandia, Uberlândia, MG (BRA).
    Combined effect of the interlayer temperature with travel speed on features of thin wall WAAM under two cooling approaches2023Inngår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 126, s. 273-289Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This work presents the evaluation of the interlayer temperature (IT) with travel speed (TS) combined effect for a given wire feed speed (WFS) on operational, geometrical, and metallurgical features of thin walls with the same width deposited by wire arc additive manufacturing (WAAM) with a low alloy steel, using or not active cooling. A preliminary experimental design was carried out to define a range of IT that could prevent the molten pool from running down and, then, be used in the main experimental design. The main tests were planned and performed to find different IT and TS combinations for a given WFS capable of depositing walls with the same target effective wall width. After selecting the parameters, six walls were deposited, three under natural cooling (NC) and three under near immersion active cooling (NIAC). A more significant temperature variability along the layer length (ΔT/ΔLL) is observed in increasing IT-TS combination and under NIAC. Regardless of the cooling approach, a worse surface aspect was observed with lower IT and TS. However, NC or NIAC do not affect the wall width (effective or external) or the layer height. On the other hand, they are affected by the IT with TS combination. A shorter production time was obtained on the walls with NIAC and higher IT-TS. No marked microstructural differences were observed comparing the walls, regardless of the cooling approach. However, microstructure tempering (hardness reduction) was observed in the walls deposited with NC using higher IT levels.  

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  • 35.
    Teixeira, Felipe Ribeiro
    et al.
    Federal University of Uberlandia (UFU), Center for Research and Development of Welding Processes (LAPROSOLDA), Uberlândia, MG (BRA).
    Scotti, Fernando Matos
    Federal University of Uberlandia (UFU), Center for Research and Development of Welding Processes (LAPROSOLDA), Uberlândia, MG (BRA).
    Reis, Ruham Pablo
    Federal University of Uberlandia (UFU), Center for Research and Development of Welding Processes (LAPROSOLDA), Uberlândia, MG (BRA).
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Federal University of Uberlandia (UFU), Center for Research and Development of Welding Processes (LAPROSOLDA), Uberlândia, MG (BRA); Federal University of Parana (UFPR), Graduate Program in Materials Science and Engineering, Curitiba, PR (BRA).
    Effect of the CMT advanced process combined with an active cooling technique on macro and microstructural aspects of aluminum WAAM2021Inngår i: Rapid prototyping journal, ISSN 1355-2546, E-ISSN 1758-7670, Vol. 27, nr 6, s. 1206-1219Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose: This paper aims to assess the combined effect of the Cold Metal Transfer (CMT) advanced process and of a thermal management technique (near immersion active cooling [NIAC]) on the macro and microstructure of Al wall-like preforms built by wire arc additive manufacturing (WAAM). As specific objective, it sought to provide information on the effects of the electrode-positive/electrode-negative (EP/EN) parameter in the CMT advanced process fundamental characteristics. Design/methodology/approach: Initially, bead-on-plate deposits were produced with different EP/EN ratios, still keeping the same deposition rate, and the outcomes on the electrical signal traces and bead formation were analyzed. In a second stage, the EP/EN parameter and the layer edge to water distance (LEWD) parameter from the NIAC technique were systematically varied and the resultant macro and microstructures compared with those formed by applying natural cooling. Findings: Constraints of EP/EN setting range were uncovered and discussed. The use of the NIAC technique favors the formation of finer grains. For a given EP/EN value, a variation in the NIAC intensity (LEWD value) showed marginal effect on grain size. When the EP/EN parameter effect is isolated, i.e. for a given LEWD setting, it was observed that an increase in the EP/EN level favors coarser grains. Originality/value: Both the EP/EN parameter and the use of an active cooling technique (NIAC) might be used, even in combination, as effective tools for achieving proper macro and microstructure in WAAM of thin wall builds. 

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  • 36.
    Teixeira, Felipe Ribeiro
    et al.
    Center for Research and Development of Welding Processes, Federal University of Uberlandia, Uberlândia, MG(BRA).
    Scotti, Fernando Matos
    Center for Research and Development of Welding Processes, Federal University of Uberlandia, Uberlândia, MG (BRA).
    Vilarinho, Louriel Oliveira
    Center for Research and Development of Welding Processes, Federal University of Uberlandia, Uberlândia, MG (BRA).
    da Mota, Carlos Alberto Mendes
    Department of Mechanical Engineering, Federal University of Pará, Belém, PA (BRA).
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Center for Research and Development of Welding Processes, Federal University of Uberlandia, Uberlândia, MG (BRA).
    Transferability of the working envelope approach for parameter selection and optimization in thin wall WAAM2021Inngår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 119, nr 1-2, s. 969-989Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This work aims to propose and assess a methodology for parameterization for WAAM of thin walls based on a previously existing working envelope built for a basic material (parameter transferability). This work also aimed at investigating whether the working envelope approach can be used to optimize the parameterization for a target wall width in terms of arc energy (which governs microstructure and microhardness), surface finish and active deposition time. To reach the main objective, first, a reference working envelope was developed through a series of deposited walls with a plain C-Mn steel wire. Wire feed speed (WFS) and travel speed (TS) were treated as independent variables, while the geometric wall features were considered dependent variables. After validation, three combinations of WFS and TS capable of achieving the same effective wall width were deposited with a 2.25Cr-1Mo steel wire. To evaluate the parameter transferability between the two materials, the geometric features of these walls were measured and compared with the predicted values. The results showed minor deviations between the predicted and measured values. As a result, WAAM parameter selection for another material showed to be feasible after only fewer experiments (shorter time and lower resource consumption) from a working envelope previously developed. The usage of the approach to optimize parameterization was also demonstrated. For this case, lower values of WFS and TS were capable of achieving a better surface finish. However, higher WFS and TS are advantageous in terms of production time. As long as the same wall width is maintained, variations in WFS and TS do not significantly affect microstructure and microhardness.

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  • 37.
    Valiente Bermejo, María Asunción
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Eynian, Mahdi
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Malmsköld, Lennart
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    University-industry collaboration in curriculum design and delivery: A model and its application in manufacturing engineering courses2021Inngår i: Industry & higher education, ISSN 0950-4222, E-ISSN 2043-6858, Vol. 36, nr 5Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The advantages and importance of university-industry collaboration, particularly in curriculum design and delivery, are well-known. However, although curriculum development models are available in the literature, very few are sufficiently concrete to be applicable in practice or are generalizable beyond their discipline of origin. In this paper, a co-operative model based on the Plan-Do-Study-Act cycle is presented and described. An example of its application in the curriculum design of two courses in welding within a Manufacturing Engineering Master's program is detailed. The model was found successful based on the evaluation of the courses by students, teachers, and the industrial representatives involved. Therefore, it proved to be an effective tool for bridging the gap between industrial needs and academia in the field of Manufacturing Engineering education. At the same time, the methodology is generalizable and is applicable to any field of education.

    Fulltekst (pdf)
    Sage
  • 38.
    Yehorov, Yuri
    et al.
    Center for Research and Development of Welding Processes, Federal University of Uberlandia, Uberlândia, Brazil.
    da Silva, Leandro João
    Center for Research and Development of Welding Processes, Federal University of Uberlandia, Uberlândia, Brazil.
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Center for Research and Development of Welding Processes, Federal University of Uberlandia, Uberlândia, Brazil.
    Balancing WAAM Production Costs and Wall Surface Quality through Parameter Selection: A Case Study of an Al-Mg5 Alloy Multilayer-Non-Oscillated Single Pass Wall2019Inngår i: Journal of Manufacturing and Materials Processing, E-ISSN 2504-4494, Vol. 3, nr 2, s. 1-19Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The purpose of the study was to propose a strategy to assess the potential reduction of the production cost during wire+arc additive manufacturing (WAAM) based on the combination of wire feed speed (related to deposition rate) and travel speed (related to deposition time). A series of experiments, using a multilayer-non-oscillated single pass wall made of an Al-Mg alloy, was conducted. The quality of the wall was assessed through the lateral surface waviness and top layer undulation. The concepts of Surface Waviness and Buy-to-Apply indices were introduced. Initially, the range of travel speed (TS) that provided layers with acceptable quality was determined for a given wire feed speed (WFS), corresponding to a constant current. Then, the effect of the increase of production capacity of the process (though current raising, yet maintaining the ratio WFS/TS constant) on the wall quality for a given condition within the TS range was assessed. The results showed that the useful range of TS prevents too rough a waving surface below the lower limit and top surface undulation over the higher limit. However, inside the range, there is little quality variation for the case under study. Finally, simulations of deposition time were developed to demonstrate the weight of the TS on the final deposition time and wall quality as a function of a target wall width. This respective weight showed the existence of a complex and unpredictable, yet determined, power of a combination of TS, target wall geometry, and dead time between subsequent layers. It was verified to be possible to find optimized TS as a function of different target geometries. 

    Fulltekst (pdf)
    BalancingWAAM
  • 39.
    Yehorov, Yurii
    et al.
    Federal University of Uberlandia (UFU),Center for Research and Development of Welding Processes, Laprosolda, Uberlândia, MG 38408-100, Brazil.
    da Silva, Leandro João
    Federal University of Uberlandia (UFU),Center for Research and Development of Welding Processes, Laprosolda, Uberlândia, MG 38408-100, Brazil.
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Federal University of Uberlandia (UFU),Center for Research and Development of Welding Processes, Laprosolda, Uberlândia, MG 38408-100, Brazil.
    Exploring the use of switchback for mitigating homoepitaxial unidirectional grain growth and porosity in WAAM of aluminium alloys2019Inngår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 104, nr 1-4, s. 1581-1592Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, an alternative approach to prevent unidirectional grain growth in wire + arc additive manufacturing (WAAM) is proposed and assessed, by moving cyclically the torch forward and backward, likewise the welding technique known as switchback. A series of tests were planned with CMT (cold metal transfer) process to compare three wall-like build-ups, which uses different deposition patterns, namely, in one-way direction, reverse direction, and switchback. The same equivalent travel speed and number of deposited layers were kept among them. Longitudinal sections were taken to identify the grain growth behaviour. Finally, samples were removed from the walls for porosity evaluation. The results confirmed the characteristics of unidirectional grain growth, when one-way direction condition was employed, and the break of growth direction between layers, when reverse direction was used, yet a zig-zag pattern became present. Differently, the application of switchback showed no preferential or unidirectional grain growth, suggesting less anisotropy of mechanical properties. In addition, switchback reduced porosity. © 2019, The Author(s).

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