The sheet metal forming process basically involves the shaping of sheet metal of various thickness and material properties into the desired contours. This metal forming process has been extensively used by the automotive industry to manufacture both car panels and parts. Over the years numerous investigations have been conducted on various aspects of the manufacturing process with varied success. In recent years the requirements on the sheet metal forming industry have headed towards improved stability in the forming process while lowering environmental burdens. Therefore the overall aim of this research was to identify a technique for developing lubricant formulations that are insensitive to the sheet metal forming process. Due to the expense of running experiments on production presses and to improve time efficiency of the process the evaluation procedure was required to be performed in a laboratory. Preliminary investigations in the friction/lubricant system identified several laboratory tests capable of measuring lubricant performance and their interaction with process variables. However, little was found on the correlation between laboratory tests and production performance of lubricants. Therefore the focus of the research switched to identifying links between the performance of lubricants in a production environment and laboratory tests. To reduce the influence of external parameters all significant process variables were identified and included in the correlation study to ensure that lubricant formulations could be desensitised to all significant variables. The significant process variables were found to be sensitive to die position, for instance: contact pressure, blank coating of the strips and surface roughness of the dies were found significant for the flat areas of the die while no variables affected friction when polished drawbeads were used. The next phase was to identify the interaction between the significant variables and the main lubricant ingredient groups. Only the fatty material ingredient group (responsible for the formation of boundary lubricant regimes) was found to significantly influence friction with no interaction between the ingredient groups. The influence of varying this ingredient group was then investigated in a production part and compared to laboratory results. The correlation between production performance and laboratory tests was found to be test dependant. With both the Flat Face Friction test and the Drawbead Simulator unaffected by changes in the lubricant formulation, while the Flat Bottom Cup test showing similar results as the production trial. It is believed that the lack of correlation between the friction tests and the production performance of the lubricant is due to the absence of bulk plastic deformation of the strip. For this reason the Ohio State University (OSU) friction test was incorporated in the lubricant evaluation procedure along with a Flat Bottom Cup test. Finally, it is strongly believed that if the lubricant evaluation procedure highlighted in this research is followed then lubricant formulations can be developed confidently in the laboratory.

Sheet metal forming is used in a wide range of industrial processes ranging from tube manufacturing to automobile and aviation industry. It includes processes like stamping, bending, stretching, drawing and wheeling. In the past few years materials for sheet metal forming and, technology have improved a lot. The improved materials have higher strength and more ductility than conventional sheet steel and therefore they have to be worked differently. For such steels conventional methods can not be applied totally. So there is a need for constant improvement in technology. Trial and error method currently in use increases lead time and is not economic also. To overcome the problems, use of simulation software in metal forming processes has increased significantly. The rapid development of software technology accompanied with lower cost computer hardware have enabled many manufacturing operations to be modeled cost-effectively that only a few years ago would have been considered impractical. However there are some difficulties in simulation of sheet metal forming process. For example it is never an easy task to select the correct software for a particular process. Various authors ascribe different causes for the difficulties. Among them the prominent ones are lacunae in elasto-plastic modeling, material behaviour, involved complexities and a lack of good elements. Apart from that the demands of sheet metal processes are increasing both with respect to the tolerance requirements of the finished part and with regard to geometric complexity of the part to be formed. A few years ago finite elements have been developed using Papcovitch-Neuber solutions of the Navier equation for the displacement function. Among these elements PN5X1 has the abilities to predict both displacements and stresses accurately. And recently the element is extended to include material nonlinearity and is working well for the small deformation range. To use this element for sheet metal forming it is necessary that the element should predict correct results for large deformations. In the present work we have further extended this element for large displacements and large rotation. In the literature there are various algorithms recommended for use with large deformation. Among them we have selected a suitable algorithm and verified its usefulness. First we have taken a simple truss and applied loads to cause large deflection. We observe adequate convergence with the chosen algorithm and then we extend it to PN5X1. in large deformation analysis, equilibrium is computed about the deformed shape. In the chosen algorithm we apply incremental loading and within each load step loop we iterate for equilibrium. We ensure error free solution (equilibrium) before additional loading is introduced. With the help of flowchart these processes have been depicted. A computer program in C, based on the above incremental method and equilibrium check has been written. For the purpose of verification of the program, we have solved some benchmark tests. We start with linear cases and then attempt a number of geometric nonlinear problems like- cantilever subjected to end shear, pinched cylinder with open end etc. We have also included the classical benchmark problem of the cantilever subjected to end moment. The present algorithm gives solutions which are in excellent agreement with those reported in the literature. Finally, we look at some aspects of the problem which require further investigation.

This thesis illustrates analysis of the influence of the non-machining processes on product quality by experimental design and statistical analysis. For the analysis objective / dishwasher production in Arcelik Dishwasher plant is examined. Sheet metal forming processes of dishwasher production constitutes the greatest portion of production cost and using the Pareto analysis technique / four pieces among twenty six pieces are determined to be investigated. These four pieces are the U Sheet, L Sheet, Inner Door and Side Panel of the dishwasher. By the help of the flow diagrams production process of the determined pieces are defined. Brainstorming technique and cause&amp / effect diagrams are used to determine which non-machining process parameters can cause pieces to be scrapped. These parameters are used as control factors in experimental design. Taguchi&amp / #8217 / s L16(215) orthogonal array, Taguchi&amp / #8217 / s L16(215) orthogonal array using S/N transformation and 28-4 fractional factorial design are used on purpose. With repetitions and confirmation experiments the effective parameters are determined and optimum level of these parameters are defined for the improvements on scrap quantity and quality of production.

The objective of the current study is the development of an optimization methodology for the energy efficiency of the cold roll forming process. Towards that target, a hybrid modeling approach, utilizing analytical and computational models, is proposed and developed. The energy efficiency indicator for the cold roll forming process is defined, as taking into account the cold roll forming process as a system with energy inputs and outputs. An analytical model was proposed and analyzed for the calculation of such energy efficiency indicator. Internal deformation work for longitudinal and bending strains and pulling frictional work were taking into account. Validation of the analytical model with experimental data and a sensitivity analysis for cold roll forming process variables are then presented. Furthermore a computational model for the cold roll forming process was proposed and analyzed. Simulation methods and modeling approach are analyzed for both forming and springback analysis. The computational model sections and variables are analyzed and results for longitudinal strains are validated with experimental data. The aforementioned modeling approaches were integrated within an optimization methodology, which consist of a robust design algorithm and a closed loop checking for quality constraints. A robust design algorithm implementation was proposed utilizing the analytical model, as taking into account the uncertainty of noise factors within computer experiments. Closed loop checking of quality constraints is implemented using computational model and specified process guidelines. The main outcome of this work is the complete method that was proposed and realized through analytical and computational models. The evaluation of the case study revealed the efficiency and practicality of the suggested approach towards energy efficiency optimization of the cold roll forming process. / Το αντικείμενο αυτής της διατριβής είναι η ανάπτυξη μιας μεθοδολογίας βελτιστοποίησης της ενεργειακής αποδοτικότητας της διεργασίας διαμόρφωσης με περιστρεφόμενους κυλίνδρους. Προς αυτόν τον στόχο, μια υβριδική προσέγγιση μοντελοποίησης, χρησιμοποιώντας αναλυτικό και υπολογιστικό μοντέλο, προτείνεται και αναπτύσσεται. Ο δείκτης ενεργειακής αποδοτικότητας για την διεργασία διαμόρφωσης με περιστρεφόμενους κυλίνδρους ορίζεται, λαμβάνοντας υπόψη τη διεργασία ως ένα σύστημα με ενεργειακές εισροές και εκροές. Ένα αναλυτικό μοντέλο προτείνεται και αναλύεται για τον υπολογισμό του δείκτη ενεργειακής αποδοτικότητας. Υπολογίζονται το εσωτερικό έργο παραμόρφωσης για διαμήκεις και κάμψης παραμορφώσεις, και έργο τριβής μέσω έλξης του υλικού. Το αναλυτικό μοντέλο επαληθεύεται με πειραματικές παρατηρήσεις και στην συνέχεια πραγματοποιείται μία ανάλυση ευαισθησίας για της μεταβλητές της διεργασίας διαμόρφωσης με περιστρεφόμενους κυλίνδρους. Επιπροσθέτως, ένα υπολογιστικό μοντέλο για την διεργασία διαμόρφωσης με περιστρεφόμενους κυλίνδρους προτείνεται και αναλύεται. Οι μέθοδοι προσομοίωσης και η προσέγγιση μοντελοποίησης αναλύονται για τις αναλύσεις διαμόρφωσης και επαναφοράς. Τα τμήματα του υπολογιστικού μοντέλου και οι μεταβλητές του αναλύονται καθώς και τα αποτελέσματα για τις διαμήκεις παραμορφώσεις επαληθεύονται με πειραματικά δεδομένα. Οι εν λόγω προσεγγίσεις μοντελοποίησης ενσωματώνονται σε μία μεθοδολογία βελτιστοποίησης, η οποία αποτελείται από έναν αλγόριθμο εύρωστου σχεδιασμού και έναν κλειστό βρόγχο για τον έλεγχο των ποιοτικών περιορισμών. Η υλοποίηση του αλγόριθμου εύρωστου σχεδιασμού προτείνεται με χρήση του αναλυτικού μοντέλου, παίρνοντας υπόψη την αβεβαιότητα των μεταβλητών θορύβου σε πειράματα με Η/Υ. Ο κλειστός βρόγχος για τον έλεγχο των ποιοτικών περιορισμών χρησιμοποιεί το υπολογιστικό μοντέλο και συγκεκριμένες οδηγίες διεργασίας. Το κύριο αποτέλεσμα αυτής της εργασίας είναι η πλήρης μεθοδολογία που προτείνεται και πραγματοποιείται μέσω αναλυτικού και υπολογιστικού μοντέλων. Η αξιολόγηση της εφαρμογής της μεθοδολογίας σε βιομηχανικό προϊόν αποκάλυψε την αποτελεσματικότητα και την πρακτικότητα της προτεινόμενης προσέγγισης για την βελτιστοποίηση της ενεργειακής αποδοτικότητας της διεργασίας διαμόρφωσης με περιστρεφόμενους κυλίνδρους.

O atrito na interface entre a peça e a ferramenta tem considerável importância em operações de estampagem de chapas, são necessários conhecimentos precisos sobre processos de conformação de chapas para a análise e projeto de novas peças e ferramentas, assim como para validação de uma simulação numérica. Este trabalho usa o método de determinação do coeficiente de atrito em estampagem através do ensaio de dobramento sob tensão e avalia sua precisão com o uso do software de elementos finitos LS-DYNAFORM, específico para esse processo de fabricação. Como existem seis equações que calculam o coeficiente de atrito para o mesmo ensaio de dobramento sob tensão, foram testadas todas as equações com o objetivo de verificar se existe variação entre os resultados. O material de estudo foi o alumínio comercialmente puro, liga AA1100. Os resultados indicam que há certa variação para cada equação usada, principalmente para aquelas que consideram o torque no pino. É observada também uma tendência do software a se distanciar dos resultados práticos por considerar o atrito como uma constante ao longo do processo. A pressão de contato entre o pino e a chapa no ensaio de dobramento sob tensão também foi avaliada através de um filme que tem a capacidade de registrar a pressão aplicada juntamente com a medição da força vertical aplicada ao pino. Os resultados indicam que a força vertical é mais precisa para se definir a pressão de contato ao uso de equações pré-estabelecidas e que a área de atuação da chapa no pino é sempre menor que a área calculada geometricamente. Por fim, para se saber qual é o comportamento do atrito para altas pressões, o ensaio de dobramento sob tensão foi feito com força variável e constatou-se que o atrito diminui com o aumento das pressões. No entanto, os valores iniciais da curva de atrito versus pressão de contato não foram obtidos pois nesse caso seria necessário usar uma máquina diferente da usada nesse estudo, ou seja, que não use pressão de óleo para acionamento e movimentação da chapa. / Friction at the interface of workpiece and tooling has a considerably importance in sheet metal forming operations. It is necessary an accurate knowledge for the analysis and design of new workpieces and tooling, as well as for the validation of a numeric simulation. This work uses the bending under tension test to determining the friction coefficient in sheet metal forming and evaluates its accuracy using the finite element software LS-DYNAFORM, specific to this manufacturing process. Since there are six equations that calculate the coefficient of friction for the same bending under tension test, all equations were tested in order to verify if there is much variation between the results. The material used in these work was pure commercial aluminum alloy AA1100. The results indicate that there is some variation for each equation used, especially for those that consider the torque on the pin. It was also observed a tendency for software to distance themselves from practical results considering friction as a constant throughout the process. It is also observed a tendency for the software to generate curves away from the tests as the friction increases. The contact pressure between the pin and the sheet in the bending under tension test was also evaluated through a film that has the ability to measure the pressure applied, together with the measurement of the vertical force applied to the pin. The results indicate that the vertical force is more accurate to define the contact pressure than equations previously established for this and that the contact area between the sheet and the pin is always smaller than the area calculated geometrically. Finally, to know the behavior of the friction at high pressures, the bending under tension test was done with variable forces and it was found that the friction decreases with increasing the pressure, which is in full agreement with the theory.

O atrito na interface entre a peça e a ferramenta tem considerável importância em operações de estampagem de chapas, são necessários conhecimentos precisos sobre processos de conformação de chapas para a análise e projeto de novas peças e ferramentas, assim como para validação de uma simulação numérica. Este trabalho usa o método de determinação do coeficiente de atrito em estampagem através do ensaio de dobramento sob tensão e avalia sua precisão com o uso do software de elementos finitos LS-DYNAFORM, específico para esse processo de fabricação. Como existem seis equações que calculam o coeficiente de atrito para o mesmo ensaio de dobramento sob tensão, foram testadas todas as equações com o objetivo de verificar se existe variação entre os resultados. O material de estudo foi o alumínio comercialmente puro, liga AA1100. Os resultados indicam que há certa variação para cada equação usada, principalmente para aquelas que consideram o torque no pino. É observada também uma tendência do software a se distanciar dos resultados práticos por considerar o atrito como uma constante ao longo do processo. A pressão de contato entre o pino e a chapa no ensaio de dobramento sob tensão também foi avaliada através de um filme que tem a capacidade de registrar a pressão aplicada juntamente com a medição da força vertical aplicada ao pino. Os resultados indicam que a força vertical é mais precisa para se definir a pressão de contato ao uso de equações pré-estabelecidas e que a área de atuação da chapa no pino é sempre menor que a área calculada geometricamente. Por fim, para se saber qual é o comportamento do atrito para altas pressões, o ensaio de dobramento sob tensão foi feito com força variável e constatou-se que o atrito diminui com o aumento das pressões. No entanto, os valores iniciais da curva de atrito versus pressão de contato não foram obtidos pois nesse caso seria necessário usar uma máquina diferente da usada nesse estudo, ou seja, que não use pressão de óleo para acionamento e movimentação da chapa. / Friction at the interface of workpiece and tooling has a considerably importance in sheet metal forming operations. It is necessary an accurate knowledge for the analysis and design of new workpieces and tooling, as well as for the validation of a numeric simulation. This work uses the bending under tension test to determining the friction coefficient in sheet metal forming and evaluates its accuracy using the finite element software LS-DYNAFORM, specific to this manufacturing process. Since there are six equations that calculate the coefficient of friction for the same bending under tension test, all equations were tested in order to verify if there is much variation between the results. The material used in these work was pure commercial aluminum alloy AA1100. The results indicate that there is some variation for each equation used, especially for those that consider the torque on the pin. It was also observed a tendency for software to distance themselves from practical results considering friction as a constant throughout the process. It is also observed a tendency for the software to generate curves away from the tests as the friction increases. The contact pressure between the pin and the sheet in the bending under tension test was also evaluated through a film that has the ability to measure the pressure applied, together with the measurement of the vertical force applied to the pin. The results indicate that the vertical force is more accurate to define the contact pressure than equations previously established for this and that the contact area between the sheet and the pin is always smaller than the area calculated geometrically. Finally, to know the behavior of the friction at high pressures, the bending under tension test was done with variable forces and it was found that the friction decreases with increasing the pressure, which is in full agreement with the theory.

Entre os processos de fabricação mecânicos atuais destacam-se os processos de conformação de chapas metálicas devido à sua produtividade e confiabilidade e a seus baixos custos de produção, baixo consumo de material e produtos nos formatos bem próximos dos esperados nas fases de projeto. Isto só é possível se todas as variáveis do projeto e do processo estiverem conforme as especificações prévias, exigidas principalmente em setores da indústria tais como o aeronáutico e o automobilístico. Um recurso útil para se alcançar estas expectativas é o estudo da estricção e da conformabilidade em chapas metálicas, representadas em diagramas de limite de conformação (DLC), os quais, aliados à análise numérica através do Método dos Elementos Finitos, permitem predições a respeito das variáveis de projeto. Este trabalho tem como objetivos rever e aplicar conceitos relativos a estes aspectos. O objetivo principal deste trabalho é de dispor uma metodologia de avaliação e otimização para o processo de estampagem, utilizando-se elementos finitos e DLC. Uma modificação no método de Marciniak-Kuczynski é utilizada para a obtenção do DLC. Busca-se com isto uma contribuição para a redução de custos em aplicações industriais com o uso desta metodologia através da diminuição das fases de tentativas e erros em projeto e reforma de estampos (try-outs). / Nowadays, sheet metal forming processes have an important role amongst the mechanical manufacturing processes, because they are characterized by high productivity and reliability at low cost, low material waste and near net shapes from design. This is achieved by controlling the design and process parameters according to initial constraints. This scenario is common at aeronautic and at automobilistic productions . These results are obtained by studies of necking and formability in sheet metals and by the use of forming limit diagrams (FLD) and finite element numerical analysis to predict design parameters. This work reviews these concepts and presents a methodology for optimization of deep drawing processes, by using finite element method and FLD. A modification of the Marciniak-Kuczynski method has been introduced to obtain the FLD. Once this methodology has been performed, it can be possible to reduce try-outs in sheet metal dies and costs reduction can also be obtained.

Em anos recentes, os processos de conformação de chapas automotivas têm sido drasticamente modificados. A utilização de equipamentos de medição metrológicos óticos sem contato e respectivos softwares baseados em fotogrametria, bem como o uso de programas de simulação de estampagem baseados no Método dos Elementos Finitos (FEM), estão se tornando uma rotina no desenvolvimento de ferramentais de estampagem, visto que a confiabilidade, precisão de resultados e facilidade de uso em relação à topologia superficial do ferramental, representou um grande salto tecnológico. Entretanto, por maior que tenha sido o avanço, persistem ainda problemas relacionados ao custo benefício quanto à adoção de certas técnicas e a possibilidade de utilizar ambos os sistemas de forma a um complementar o outro. Neste sentido, o objetivo desta tese é analisar o processo de conformação de chapas utilizando simulação computacional e engenharia reversa como ferramentas integradas no desenvolvimento e construção de estampos automotivos. São descritos casos industriais, cujos resultados demonstram que novas técnicas podem ser aplicadas na definição e modelagem do processo de estampagem de chapas metálicas, utilizando a metrologia ótica, engenharia reversa e a simulação computacional baseada no Método dos Elementos Finitos. / In recently years, sheet metal forming processes used in automotive industry have been drastically modified. The use of non-contact measurement devices based on optical metrology and respective software based on photogrammetry, and the use of stamping simulation programs based on Finite Element Method (FEM), are becoming a routine in the development of tools for stamping, visa that reliability, accuracy of results and ease of use, in relation to the tooling surface topology, was a major technology leap. However, although this advancement, there are still remaining problems related to the cost benefit of the adoption of certain techniques, and the possibility of the use of both systems, in order to complement one another. In this sense, the aims of this thesis is to analyze the sheet metal forming process using computer simulation and reverse engineering as integrated tools in design and construction of automotive dies. Industry cases are described, whose results show that new techniques can be applied in definition and modeling of stamping metal sheets process, using optical metrology, reverse engineering and computer simulation based on Finite Element Method.

Dentre os principais problemas que ocorrem na estampagem de chapas metálicas estão a fratura, e estricção (necking) e o enrugamento (wrinkling). Este último pode fazer com que a peça fabricada seja rejeitada por problemas que vão desde motivos estéticos até dificuldades de montagem destas peças e desgaste excessivo da ferramenta. Diversos pesquisadores tem estudado o problema de instabilidade à compressão que origina o fenômeno de enrugamento. Pretende-se estudar os principais métodos para predição do enrugamento, a saber, a teoria da bifurcação, a introdução de uma falha induzida e a aplicação do indicador proposto por Nordlund e Häggblad (coeficiente NH). O método escolhido será implementado junto a um programa de análise por elementos finitos de modo a obter diagramas limite de estabilidade, para então ser aplicado a peças mais genéricas. O procedimento é aplicado a peças de geometria relevante para serem ensaiadas experimentalmente de modo a validar as simulações numéricas propostas. / Among the main problems in sheet metal forming processes are the fracture, the necking and the wrinkling behavior of the material. The last one can produce rejected parts due difficulties in the assembly of these parts or excessive wear of the tooling. Many researchers have been studied the problem of the compression instability phenomenon that origins the wrinkling behavior. The objective of this work is the study of the main available methods to the wrinkling prediction, as the bifurcation theory, the induced defect and an indicator proposed by Nordlund and Häggblad (NH coefficient). The more suitable method is implemented into a finite element analysis software in order to obtain the stability limit diagrams that can be used in the design of generic shape parts. Experimental studies will be done in parts subjected to compressive forming loads in order to validate the numerical simulations.

O atrito na interface entre a peça e a ferramenta tem considerável importância em operações de estampagem de chapas, são necessários conhecimentos precisos sobre processos de conformação de chapas para a análise e projeto de novas peças e ferramentas, assim como para validação de uma simulação numérica. Este trabalho usa o método de determinação do coeficiente de atrito em estampagem através do ensaio de dobramento sob tensão e avalia sua precisão com o uso do software de elementos finitos LS-DYNAFORM, específico para esse processo de fabricação. Como existem seis equações que calculam o coeficiente de atrito para o mesmo ensaio de dobramento sob tensão, foram testadas todas as equações com o objetivo de verificar se existe variação entre os resultados. O material de estudo foi o alumínio comercialmente puro, liga AA1100. Os resultados indicam que há certa variação para cada equação usada, principalmente para aquelas que consideram o torque no pino. É observada também uma tendência do software a se distanciar dos resultados práticos por considerar o atrito como uma constante ao longo do processo. A pressão de contato entre o pino e a chapa no ensaio de dobramento sob tensão também foi avaliada através de um filme que tem a capacidade de registrar a pressão aplicada juntamente com a medição da força vertical aplicada ao pino. Os resultados indicam que a força vertical é mais precisa para se definir a pressão de contato ao uso de equações pré-estabelecidas e que a área de atuação da chapa no pino é sempre menor que a área calculada geometricamente. Por fim, para se saber qual é o comportamento do atrito para altas pressões, o ensaio de dobramento sob tensão foi feito com força variável e constatou-se que o atrito diminui com o aumento das pressões. No entanto, os valores iniciais da curva de atrito versus pressão de contato não foram obtidos pois nesse caso seria necessário usar uma máquina diferente da usada nesse estudo, ou seja, que não use pressão de óleo para acionamento e movimentação da chapa. / Friction at the interface of workpiece and tooling has a considerably importance in sheet metal forming operations. It is necessary an accurate knowledge for the analysis and design of new workpieces and tooling, as well as for the validation of a numeric simulation. This work uses the bending under tension test to determining the friction coefficient in sheet metal forming and evaluates its accuracy using the finite element software LS-DYNAFORM, specific to this manufacturing process. Since there are six equations that calculate the coefficient of friction for the same bending under tension test, all equations were tested in order to verify if there is much variation between the results. The material used in these work was pure commercial aluminum alloy AA1100. The results indicate that there is some variation for each equation used, especially for those that consider the torque on the pin. It was also observed a tendency for software to distance themselves from practical results considering friction as a constant throughout the process. It is also observed a tendency for the software to generate curves away from the tests as the friction increases. The contact pressure between the pin and the sheet in the bending under tension test was also evaluated through a film that has the ability to measure the pressure applied, together with the measurement of the vertical force applied to the pin. The results indicate that the vertical force is more accurate to define the contact pressure than equations previously established for this and that the contact area between the sheet and the pin is always smaller than the area calculated geometrically. Finally, to know the behavior of the friction at high pressures, the bending under tension test was done with variable forces and it was found that the friction decreases with increasing the pressure, which is in full agreement with the theory.