Esta tese tem por objetivo determinar a estampabilidade de chapas de alumínio 5083 O processadas pelo processo de fricção e mistura (PFM). Para atingir os objetivos propostos o processo de fricção por mistura foi estudado e uma ferramenta de soldagem PFM construída, a verificação da qualidade da solda foi realizada com metalografia da região processada para verificar a presença de vazios, obtidas as melhores condições a superplasticidade através do processo PFM é estudada com os ensaios de tração a quente e de saltos. Ensaios de tração a frio foram realizados nos corpos de prova com o processamento e sem o processamento com o objetivo de obter a curva tensão versus deformação do material processado e sem processamento. Foi efetuado o ensaio de microdureza da região soldada. A estampabilidade das chapas foi verificada através do ensaio de expansão hidrostática e empregadas na determinação da conformabilidade das chapas processadas e sem processar. Os ensaios de expansão hidrostática foram realizados em software de elementos finitos com o objetivo de comparar os resultados práticos e teóricos. Este estudo simulou pelo método dos elementos finitos a determinação da curva limite de conformação de chapas de alumínio 5083 O processadas através do processo PFM. A simulação de elementos finitos implicou em utilizar o método não linear e os softwares MSC MARC e Abaqus para simulação. Determinou-se neste estudo que a resistência à tração de chapas após processo PFM é 30% maior do que sem processamento, a estampabilidade à frio das chapas manteve-se a mesma. Os testes práticos determinaram que os softwares Abaqus e MSC MARC possuem boa aproximação para o teste de expansão hidrostática à frio. O Software Abaqus apresentou dificuldades para convergir e tempo de processamento muito superior ao MSC MARC nos estudos de expansão hidrostática à frio e na condição superplástica. Através dos ensaios de saltos determinou-se que a condição 328 rpm e 65 mm/min possui coeficiente de sensibilidade à taxa de deformação m muito superior ao do alumínio 5083 O sem PFM, isto resultou em uma melhor distribuição de espessura da chapa após o ensaio de expansão hidrostática superplástico em software. / The aim of this study is to determine the sheet metal formability of 5083 O aluminum sheets after friction stir processing \"FSP\". To achieve the proposed objectives the friction stir processing was be reviewed and modeled in order to enable the design and manufacture of a proper FSP tool. The quality of the process was carried out through metallographic tests of the FSP region looking for the presence of voids. The best conditions for plasticity and superplastic forming after FSP was studied by means of an approach of jump steps in the hot tensile tests, looking for a coefficient of strain rate sensitivity. The micro hardness tests and tensile tests at room temperature were carried out for the specimens with and without FSP processing in order to characterize their material mechanical behavior. The formability of the FSP blanks was evaluated through Bulge tests. The results enable to plot Forming Limit Curves friction stir processed blanks after FSP and without FSP. The numerical simulation of the Free Bulge tests was carried out using a Finite Element Method model in order to compare the numerical theoretical and experimental practical results. The numerical simulation approach allows for the determination the forming limit curve of 5083 O aluminum sheets processed by the FSP process. The Finite Element Method modeling and simulation have employed two nonlinear FEM codes: the MSC MARC and Abaqus were compared as software for the simulations. The Yeld Strength of specimens with FSP increased 30% in comparison with specimens without FSP in cold tensile tests, the formability of shapes with and without FSP was de same. The practical tests showed that Abaqus and MSC MARC results has a good approach, the processing time in Abaqus was much greater than in MSC MARC, Abaqus had convergence problems when contact condition is applied. Through the jump tensile tests the 328 rpm and 65 mm/min condition showed a m factor much higher in comparison with condition without FSP in AA 5083 O, this results led in a better thickness distribution after the superplastic bulge test in software.

Os processos de conformação de metais, apesar de sua extensa aplicação na indústria, tem seus projetos baseados principalmente em técnicas experimentais. Com o desenvolvimento e facilidade de acesso a computadores mais potentes, tornou-se viável a utilização de soluções numéricas como ferramentas de otimização das características do produto, do processo, bem como de seu custo. Um método numérico amplamente utilizado para simulação do processo de conformação é o Método dos Elementos Finitos, que permite a previsão do comportamento do fluxo de material durante a operação de conformação de chapas. Considera-se um blank com perfil ideal aquele onde a peça produzida a partir de sua conformação possua uma flange constante, minimizando ou eliminando a operação de retirada da rebarba. Com o objetivo de se obter o blank com perfil ideal para operação de conformação de chapas, desenvolveu-se uma metodologia de otimização geométrica da forma do blank, que trabalha integrada a um software comercial de análise pelo Método dos Elementos Finitos, o ANSYS/LS-Dyna3D. Apresentam-se os resultados aplicados à simulação da estampagem de uma peça prismática de base quadrada, como meio de validação da metodologia de otimização proposta. / The metal forming processes have extensive industrial application although their projects are based mainly in experimental techniques. With the development of more powerful computers, the use of numerical methods to design, simulate and optimize costs of such processes has become possible. Among the numerical methods, the Finite Element Method have large application in forming simulation, since it allows the prediction of the material flow during the sheet metal forming process. Ideal blank shape is that one which produces a part with constant flange, minimizing or eliminating trimming operations. In order to determine the ideal blank shape, this work developed a methodology to blank shape optimization. This optimization methodology has been integrated to a commercial Finite Element analysis software, the ANSYS/LS-Dyna3D. The results applied to a simulation of a square cup part are showed and discussed in order to validate the proposed optimization methodology.

A aplicação de chapas de aço como revestimento em matrizes de forjamento a quente tem sido estudada como uma alternativa inovadora, dentro de um projeto de cooperação internacional titulado “Evaluation of Sheet Metal Covers to Improve Tool Life in Forging”. Pesquisa realizada em parceria com a Alemanha pelo programa BRAGECRIM. Essas chapas serviriam como um metal de sacrifício em matrizes de forjamento a quente, que pretende substituir tratamentos superficiais de alto custo. As limitações geométricas e propriedades mecânicas das chapas garantiriam o sucesso ou não da gravura conforme o design exigido pela ferramenta, como também o número de ciclos de forjamento mantendo-se a integridade. Desta forma, o conhecimento das propriedades mecânicas em chapas e ductilidade torna-se fundamental para garantir os limites de aplicabilidade. Portanto, este trabalho tem como objetivo avaliar as propriedades mecânicas e os aspectos metalúrgicos em diferentes temperaturas de duas chapas de alta resistência DP600 e Hardox450®, os quais possuem diferentes microestruturas e ductilidade. Esta escolha se deve as diferentes aplicações que ambos os materiais possuem na indústria automobilística, devido as suas propriedades físicas, com a hipótese que influenciará na aplicação como máscaras que irão proteger as matrizes. Para isso foram realizados ensaios de dureza após ciclos de aquecimento e tração em diferentes temperaturas, com taxa de deformação controlada, simulando as condições térmicas que o material irá suportar durante o processo de forjamento. Para avaliar a ductilidade das chapas foi realizado o ensaio de estiramento biaxial. Uma análise pelo método de elementos finitos foi utilizada no ensaio de estiramento de punção esférico Erichsen, o qual foi possível pela análise de laboratório validar os experimentos e então a realização da simulação de estampagem de uma geometria bi radial em formato de copo. Os resultados de tração e dureza mostram que o DP600 possui considerável resistência mecânica em altas temperaturas com boa ductilidade, porém não maior que o Hardox450®, que perde em termos de ductilidade devido a fenômenos de fragilização em altas temperaturas. A simulação numérica permitiu avaliar como seria o produto estampado em uma geometria 3D, sobre os aspectos geométricos da chapa e os efeitos de anisotropia do DP600, como também suas tensões. / The application of sheet metal cover in hot forging dies has been studied as an innovative alternative, within an international project titled "Evaluation of sheet metal covers to improve tool life in forging". Research carried out in partnership with Germany under the BRAGECRIM program. The sheet metal would apply as a sacrificial membrane in the hot forging die, which intended to replace expensive surface treatments. The geometrical limitations and mechanical properties of the plates would guarantee the success or failure of the engraving according to the design required by the tool, as well as the number of forging cycles maintaining the integrity. In this way, the knowledge of the mechanical properties of the sheet metals and ductility becomes fundamental to guarantee the limits of applicability. Therefore, this work has as objective to evaluate the mechanical properties and the metallurgical aspects in different temperatures of two advanced High Strength Steel Sheets DP600 and Hardox450®, which have different microstructures and ductility. This choice is due to the different applications that both materials have in the automotive industry due to their properties, with the hypothesis that will influence the application as masks that will protect dies. Therefore, a hardness test has performed after heating cycles and tensile tests at different temperatures, with a controlled strain rate, simulating the thermal conditions that the material will withstand during the forging process. Biaxial stretching test to evaluate the ductility of the plates were performed. An inverse analysis by the finite element method was used in the Erichsen biaxial stretching test, in which it has been possible to validate the experiments and then to perform the stamping simulation of a bi-radial geometry in a cup format. The results show that the DP600 has considerable mechanical resistance at high temperatures with good ductility, but not higher than the Hardox450®, which is inferior in terms of ductility due to embrittlement phenomena at high temperatures. The numerical simulation allowed an evaluation of how the product can be stamped in a 3D geometry, the geometric aspects of the plate, the anisotropy effects of the DP600, as well as stress distributions.

Esta tese tem por objetivo determinar a estampabilidade de chapas de alumínio 5083 O processadas pelo processo de fricção e mistura (PFM). Para atingir os objetivos propostos o processo de fricção por mistura foi estudado e uma ferramenta de soldagem PFM construída, a verificação da qualidade da solda foi realizada com metalografia da região processada para verificar a presença de vazios, obtidas as melhores condições a superplasticidade através do processo PFM é estudada com os ensaios de tração a quente e de saltos. Ensaios de tração a frio foram realizados nos corpos de prova com o processamento e sem o processamento com o objetivo de obter a curva tensão versus deformação do material processado e sem processamento. Foi efetuado o ensaio de microdureza da região soldada. A estampabilidade das chapas foi verificada através do ensaio de expansão hidrostática e empregadas na determinação da conformabilidade das chapas processadas e sem processar. Os ensaios de expansão hidrostática foram realizados em software de elementos finitos com o objetivo de comparar os resultados práticos e teóricos. Este estudo simulou pelo método dos elementos finitos a determinação da curva limite de conformação de chapas de alumínio 5083 O processadas através do processo PFM. A simulação de elementos finitos implicou em utilizar o método não linear e os softwares MSC MARC e Abaqus para simulação. Determinou-se neste estudo que a resistência à tração de chapas após processo PFM é 30% maior do que sem processamento, a estampabilidade à frio das chapas manteve-se a mesma. Os testes práticos determinaram que os softwares Abaqus e MSC MARC possuem boa aproximação para o teste de expansão hidrostática à frio. O Software Abaqus apresentou dificuldades para convergir e tempo de processamento muito superior ao MSC MARC nos estudos de expansão hidrostática à frio e na condição superplástica. Através dos ensaios de saltos determinou-se que a condição 328 rpm e 65 mm/min possui coeficiente de sensibilidade à taxa de deformação m muito superior ao do alumínio 5083 O sem PFM, isto resultou em uma melhor distribuição de espessura da chapa após o ensaio de expansão hidrostática superplástico em software. / The aim of this study is to determine the sheet metal formability of 5083 O aluminum sheets after friction stir processing \"FSP\". To achieve the proposed objectives the friction stir processing was be reviewed and modeled in order to enable the design and manufacture of a proper FSP tool. The quality of the process was carried out through metallographic tests of the FSP region looking for the presence of voids. The best conditions for plasticity and superplastic forming after FSP was studied by means of an approach of jump steps in the hot tensile tests, looking for a coefficient of strain rate sensitivity. The micro hardness tests and tensile tests at room temperature were carried out for the specimens with and without FSP processing in order to characterize their material mechanical behavior. The formability of the FSP blanks was evaluated through Bulge tests. The results enable to plot Forming Limit Curves friction stir processed blanks after FSP and without FSP. The numerical simulation of the Free Bulge tests was carried out using a Finite Element Method model in order to compare the numerical theoretical and experimental practical results. The numerical simulation approach allows for the determination the forming limit curve of 5083 O aluminum sheets processed by the FSP process. The Finite Element Method modeling and simulation have employed two nonlinear FEM codes: the MSC MARC and Abaqus were compared as software for the simulations. The Yeld Strength of specimens with FSP increased 30% in comparison with specimens without FSP in cold tensile tests, the formability of shapes with and without FSP was de same. The practical tests showed that Abaqus and MSC MARC results has a good approach, the processing time in Abaqus was much greater than in MSC MARC, Abaqus had convergence problems when contact condition is applied. Through the jump tensile tests the 328 rpm and 65 mm/min condition showed a m factor much higher in comparison with condition without FSP in AA 5083 O, this results led in a better thickness distribution after the superplastic bulge test in software.

Deformation and annealing texture in the cold rolled low carbon steels is important for sheet metal forming operations and service performance. The aim of this study is to non-destructively investigate the effect of texture on magnetic anisotropy. Various samples having different textures and residual stress states, due to different % reduction in thickness, annealing and stress relieving treatment, were prepared. Texture maps were obtained by Magnetic Barkhausen noise measurements performed with 100 steps between the ranges of 00-3600 on the surface. Microstructure investigation by optical &amp / scanning electron microscopy / hardness and tension tests were performed / and texture was determined by X-Ray diffraction method. The results were compared, evaluated and discussed to establish relationship between texture and magnetic Barkhausen Noise emission.

In this thesis the sheet metal forming effects such as plastic strain and thickness changes in the crash have been investigated by numerical analysis. The sheet metal forming histories of the components of the load path that absorbs the highest energy during a frontal crash have been considered. To find out the particular load path, the frontal crash analysis of Ford F250 Pickup has been performed at 56 kph into a rigid wall with finite element analysis without considering the forming history. The sheet metal forming simulations have been realized for each structural component building up the particular load path. After forming histories have been acquired, plastic strain and thickness distributions have been transferred to the frontal crash analysis. The frontal crash analysis of Ford F250 Pickup has been repeated by including these to introduce the effect of forming on crash response of the vehicle. The results of the simulations with and without forming effect have been compared with the physical crash test results to evaluate the sheet metal forming effect on the overall crash response. The results showed that with forming history the crash response of the vehicle and deformations of the particular components have been changed and the maximum deceleration pulse transferred to the passenger compartment has decreased. It has seen that a good agreement with physical test results has been achieved.

Deep drawing operations are crucial for metal forming operations and manufacturing. Obtaining a defect free final product with the desired mechanical properties is very important for fulfilling the customer expectations and market competitions. Wrinkling is one of the fatal and most frequent defects that must be prevented. This study focuses on understanding the phenomenon of wrinkling and probable precautions that can be applied. In this study, dynamic &ndash / explicit commercial finite element code is used to simulate deep drawing process. The numerical experiments are compared with NUMISHEET benchmarks in order to verify the reliability of the finite element code and analysis parameters. In order to understand plastic wrinkling, the effect of blank holder force is investigated. Axisymmetrical numerical models of a cup are investigated with different blank holder forces. Wrinkling instability is illustrated in energy diagrams of the process. Effect of anisotropy on wrinkling is also discussed by comparing isotropic and anisotropic numerical experiments with the material as steel. Different drawbead models, both equivalent and physical, are implied to the problem and results are discussed. Besides numerical analysis, experimental verification is also conducted as conventional deep drawing operation by a hydraulic press. This yields to the ability to understand the effect of blank thickness on wrinkling formation through numerical and experimental analyses. The wave formations of different sized blanks with four different thicknesses are illustrated.

The Forming Limit Diagram (FLD) is a widely used concept to represent the formability of thin metallic sheets. In sheet metal forming processes, plastic instability may occur, leading to defective products. In order to manufacture defect free products, the prediction of the forming limits of sheet metals is a very important issue. FLD&rsquo / s can be obtained by several experimental, empirical and theoretical methods. However, the suitability and the accuracy of these methods for a given material may vary. In this study, FLD&rsquo / s are predicted by simulating Nakazima test using finite element software Pam-Stamp 2G. Strain propagation phenomenon is used to evaluate the limit strains from the finite element simulations. Two different anisotropic materials, AA2024-O and SAE 1006, are considered throughout the study and for each material, 7 different specimen geometries are analyzed. Furthermore, FLD&rsquo / s are predicted by theoretical approaches namely / Keeler&rsquo / s model, maximum load criteria, Swift-Hill model and Storen-Rice model. At the end of the study, the obtained FLD&rsquo / s are compared with the experimental results. It has been found that strain propagation phenomenon results for SAE 1006 are in a good agreement with the experimental results / however it is not for AA2024-O. In addition, theoretical models show some variations depending on the material considered. It has been observed that forming limit prediction using strain propagation phenomena with FE method can substantially reduce the time and cost for experimental work and trial and error process.

COMPUTER AIDED MODELING OF WRINKLING AND ITS PREVENTION PiSKiN, Mehmet Ali M.S., Department of Mechanical Engineering Supervisor: Prof. Dr. Bilgin KAFTANOgLU September 2005, 111 Pages Deep-drawing operations are performed widely in industrial applications. It is very important for efficiency to achieve parts with no defects. Wrinkling is a kind of defect caused by stresses in the flange part of the blank during metal forming operations. It is required that the flange of a workpiece in deep drawing operation should deform in its plane without wrinkling otherwise it will impair the quality of the product. To avoid wrinkling appropriate blank-holder force or drawbead can be applied. In this work, finite element method is used to obtain the wrinkling behavior. A four nodded five degree of freedom shell element is formulated. Isotropic elasto-plastic material model with Von Mises yield criterion is used. By using this shell element, the developed code can predict the bending behavior of workpiece besides membrane behavior. Simulations are carried out with four different element sizes and two different shapes (circular and rectangular). The thickness strain and nodal displacement values obtained are compared with results of a commercial finite element program and results of previously conducted experiments.

A aplicação de chapas de aço como revestimento em matrizes de forjamento a quente tem sido estudada como uma alternativa inovadora, dentro de um projeto de cooperação internacional titulado “Evaluation of Sheet Metal Covers to Improve Tool Life in Forging”. Pesquisa realizada em parceria com a Alemanha pelo programa BRAGECRIM. Essas chapas serviriam como um metal de sacrifício em matrizes de forjamento a quente, que pretende substituir tratamentos superficiais de alto custo. As limitações geométricas e propriedades mecânicas das chapas garantiriam o sucesso ou não da gravura conforme o design exigido pela ferramenta, como também o número de ciclos de forjamento mantendo-se a integridade. Desta forma, o conhecimento das propriedades mecânicas em chapas e ductilidade torna-se fundamental para garantir os limites de aplicabilidade. Portanto, este trabalho tem como objetivo avaliar as propriedades mecânicas e os aspectos metalúrgicos em diferentes temperaturas de duas chapas de alta resistência DP600 e Hardox450®, os quais possuem diferentes microestruturas e ductilidade. Esta escolha se deve as diferentes aplicações que ambos os materiais possuem na indústria automobilística, devido as suas propriedades físicas, com a hipótese que influenciará na aplicação como máscaras que irão proteger as matrizes. Para isso foram realizados ensaios de dureza após ciclos de aquecimento e tração em diferentes temperaturas, com taxa de deformação controlada, simulando as condições térmicas que o material irá suportar durante o processo de forjamento. Para avaliar a ductilidade das chapas foi realizado o ensaio de estiramento biaxial. Uma análise pelo método de elementos finitos foi utilizada no ensaio de estiramento de punção esférico Erichsen, o qual foi possível pela análise de laboratório validar os experimentos e então a realização da simulação de estampagem de uma geometria bi radial em formato de copo. Os resultados de tração e dureza mostram que o DP600 possui considerável resistência mecânica em altas temperaturas com boa ductilidade, porém não maior que o Hardox450®, que perde em termos de ductilidade devido a fenômenos de fragilização em altas temperaturas. A simulação numérica permitiu avaliar como seria o produto estampado em uma geometria 3D, sobre os aspectos geométricos da chapa e os efeitos de anisotropia do DP600, como também suas tensões. / The application of sheet metal cover in hot forging dies has been studied as an innovative alternative, within an international project titled "Evaluation of sheet metal covers to improve tool life in forging". Research carried out in partnership with Germany under the BRAGECRIM program. The sheet metal would apply as a sacrificial membrane in the hot forging die, which intended to replace expensive surface treatments. The geometrical limitations and mechanical properties of the plates would guarantee the success or failure of the engraving according to the design required by the tool, as well as the number of forging cycles maintaining the integrity. In this way, the knowledge of the mechanical properties of the sheet metals and ductility becomes fundamental to guarantee the limits of applicability. Therefore, this work has as objective to evaluate the mechanical properties and the metallurgical aspects in different temperatures of two advanced High Strength Steel Sheets DP600 and Hardox450®, which have different microstructures and ductility. This choice is due to the different applications that both materials have in the automotive industry due to their properties, with the hypothesis that will influence the application as masks that will protect dies. Therefore, a hardness test has performed after heating cycles and tensile tests at different temperatures, with a controlled strain rate, simulating the thermal conditions that the material will withstand during the forging process. Biaxial stretching test to evaluate the ductility of the plates were performed. An inverse analysis by the finite element method was used in the Erichsen biaxial stretching test, in which it has been possible to validate the experiments and then to perform the stamping simulation of a bi-radial geometry in a cup format. The results show that the DP600 has considerable mechanical resistance at high temperatures with good ductility, but not higher than the Hardox450®, which is inferior in terms of ductility due to embrittlement phenomena at high temperatures. The numerical simulation allowed an evaluation of how the product can be stamped in a 3D geometry, the geometric aspects of the plate, the anisotropy effects of the DP600, as well as stress distributions.