Comparação dos métodos de análise de deslocamento por escaneamento a laser e por elementos finitos de perfis de aço estrutural soldados
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Data
2024-01-12
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Universidade Estadual Paulista (Unesp)
Resumo
Dentre os fatores inerentes ao processo fabril, duas variáveis significativas influenciam a qualidade do cordão de solda, na fabricação e montagem das estruturas metálicas e precisam manter baixa variabilidade com limites confiáveis: a distorção e a tensão residual. Assim, este trabalho focaliza o mapeamento dessas distorções e as tensões residuais oriundas do processo de soldagem MAG e causadas pela fonte de calor. Para isso, é importante ter um método de escaneamento a laser, para analisar o comportamento do aço estrutural, mediante a aplicação da soldagem, este método foi validado através do método de elementos finitos, simulando a situação real, isso permitirá assegurar a qualidade fabril necessária. Diante disso, os perfis de aço ASTM A36 na chapa dobrada tipo U 100 x 50 x 3,04 mm e U 100 x 50 x 2,65 mm, conformados no aço ARBL CSN Civil 300, foram submetidos ao processo de soldagem e o sistema acoplado ao braço robótico Motoman UP6, usando quatro tipos de juntas experimentais com e sem ponteamentos, dois tipos de arame-eletrodos, AWS ER70S-3 e AWS ER70S-6, proteção gasosa de 75% Ar - 25% CO2 e parâmetros de soldagem que mantêm a mesma corrente. A metodologia apresentada baseia-se no escaneamento a laser instantâneo das peças a serem unidas com sobreposição de nuvem de pontos, no mesmo referencial, assessorado pelo método de elementos finitos, com o software ANSYS 2021.R2, realizando a análise matemática tridimensional. O método de escaneamento a laser avaliou diretamente a distorção no perfil dobrado e a modelagem da fonte de calor em movimento, validado pelo método de elementos finitos, considerando a dupla elipsoide de Goldak, mapeando a distribuição térmica e, consequentemente, as tensões residuais e distorções provenientes da ação do calor. Na sequência, com o auxílio de termopares, verificaram-se as temperaturas alcançadas na soldagem, as quais serviram de base para o método de elementos finitos e conferência do aporte térmico, que promovem as tensões residuais. Essas tensões devido à soldagem MAG foram medidas por equipamento de difração de raio-X, para validação do modelo por elementos finitos. Contudo, a fim de nortear as respostas do escaneamento a laser, os corpos de prova foram analisados quanto à macroestrutura, microdureza, aos resultados de teste a tração e da análise química. Os resultados obtidos com a validação do modelo numérico, através do procedimento experimental por XRD, permitiram visualizar o comportamento dessas tensões e sua origem próxima ao cordão de solda, em função da conformação sofrida. Com o processo de soldagem robotizado bem-sucedido, o escaneamento a laser foi eficaz na determinação da distorção apresentada pelos corpos de prova e validado pelo método dos elementos finitos, com alto grau de assertividade, resultando em um procedimento que pode prever as distorções também em outras condições, ou mesmo em novo procedimento de soldagem de maior penetração, assim como propiciar melhorias nas especificações de soldagem e na automação do processo de soldagem.
Among the inherent factors in the manufacturing process, two significant variables influence the quality of the weld bead in the fabrication and assembly of metal structures and need to maintain low variability with reliable limits: distortion and residual stress. Thus, this work focuses on mapping these distortions and residual stresses resulting from the MAG welding process caused by the heat source. For this purpose, it is important to have a laser scanning method to analyze the behavior of structural steel upon welding; this method was validated through the finite element method, simulating the real situation, which will ensure the necessary manufacturing quality. In this context, ASTM A36 steel profiles in U-shaped bent plates 100 x 50 x 3.04 mm and 100 x 50 x 2.65 mm, formed in ARBL CSN Civil 300 steel, were subjected to the welding process with the system coupled to the Motoman UP6 robotic arm, using four types of experimental joints with and without tack welds, two types of wire-electrodes, AWS ER70S-3 and AWS ER70S-6, gas shield of 75% Ar - 25% CO2, and welding parameters maintaining the same current. The methodology presented is based on instantaneous laser scanning of the parts to be joined with point cloud overlay, in the same frame of reference, assisted by the finite element method, using ANSYS 2021.R2 software, performing threedimensional mathematical analysis. The laser scanning method directly assessed the distortion in the bent profile and the modeling of the moving heat source, validated by the finite element method, considering the Goldak double ellipsoid, mapping the temperature distribution and consequently, the residual stresses and distortions resulting from heat action. Subsequently, with the aid of thermocouples, the temperatures reached in welding were verified, which served as a basis for the finite element method and confirmation of the thermal input, which promote residual stresses. These welding-induced stresses were measured by X-ray diffraction equipment for finite element model validation. However, in order to guide the responses of laser scanning, the test specimens were analyzed for macrostructure, microhardness, tensile test results, and chemical analysis. The results obtained with the validation of the numerical model, through the experimental XRD procedure, allowed visualizing the behavior of these stresses and their origin near the weld bead, due to the undergone conformation. With the successful robotic welding process, laser scanning was effective in determining the distortion presented by the test specimens and validated by the finite element method, with a high degree of accuracy, resulting in a procedure that can predict distortions also under other conditions, or even in a new welding procedure with greater penetration, as well as provide improvements in welding specifications and automation of the welding process.
Among the inherent factors in the manufacturing process, two significant variables influence the quality of the weld bead in the fabrication and assembly of metal structures and need to maintain low variability with reliable limits: distortion and residual stress. Thus, this work focuses on mapping these distortions and residual stresses resulting from the MAG welding process caused by the heat source. For this purpose, it is important to have a laser scanning method to analyze the behavior of structural steel upon welding; this method was validated through the finite element method, simulating the real situation, which will ensure the necessary manufacturing quality. In this context, ASTM A36 steel profiles in U-shaped bent plates 100 x 50 x 3.04 mm and 100 x 50 x 2.65 mm, formed in ARBL CSN Civil 300 steel, were subjected to the welding process with the system coupled to the Motoman UP6 robotic arm, using four types of experimental joints with and without tack welds, two types of wire-electrodes, AWS ER70S-3 and AWS ER70S-6, gas shield of 75% Ar - 25% CO2, and welding parameters maintaining the same current. The methodology presented is based on instantaneous laser scanning of the parts to be joined with point cloud overlay, in the same frame of reference, assisted by the finite element method, using ANSYS 2021.R2 software, performing threedimensional mathematical analysis. The laser scanning method directly assessed the distortion in the bent profile and the modeling of the moving heat source, validated by the finite element method, considering the Goldak double ellipsoid, mapping the temperature distribution and consequently, the residual stresses and distortions resulting from heat action. Subsequently, with the aid of thermocouples, the temperatures reached in welding were verified, which served as a basis for the finite element method and confirmation of the thermal input, which promote residual stresses. These welding-induced stresses were measured by X-ray diffraction equipment for finite element model validation. However, in order to guide the responses of laser scanning, the test specimens were analyzed for macrostructure, microhardness, tensile test results, and chemical analysis. The results obtained with the validation of the numerical model, through the experimental XRD procedure, allowed visualizing the behavior of these stresses and their origin near the weld bead, due to the undergone conformation. With the successful robotic welding process, laser scanning was effective in determining the distortion presented by the test specimens and validated by the finite element method, with a high degree of accuracy, resulting in a procedure that can predict distortions also under other conditions, or even in a new welding procedure with greater penetration, as well as provide improvements in welding specifications and automation of the welding process.
Descrição
Palavras-chave
MEF, Soldagem MAG, Ciclo térmico, Distorção, Tensão Residual, FEM, MAG welding, Thermal cycle, Distortion, Residual Stress
Como citar
PEREIRA, J. P. Comparação dos métodos de análise de deslocamento por escaneamento a laser e por elementos finitos de perfis de aço estrutural soldados. Orientador: Edson A. Capello Sousa. 2024. 259 p. Tese (Doutorado em Engenharia Mecânica) - Faculdade de Engenharia, Universidade Estadual Paulista "Júlio de Mesquita Filho", Bauru, 2024. Disponível em: https://hdl.handle.net/11449/253439. Acesso em: 26 de fev. 2024.