Die vorliegende Arbeit hat die Untersuchung des Einlaufverhaltens beim Tiefziehen von Papier und Karton zum Ziel. Genauer wird das Materialversagen, welches durch Risse der Ziehteilzarge definiert ist, während der Umformung untersucht und quantifiziert. Das auftretende Verhalten des Materialversagens wird anhand einer gezielten Analyse der Systemdaten rekonstruiert und nachvollzogen. Dabei erweist sich die Reibarbeit, welche beim Transport des Ziehteiles durch die Ziehbüchse verrichtet werden muss, als signifikante Kenngröße zur Beschreibung des Materialversagens. Basierend auf dieser Ersatzkenngröße wird ein Modellentwurf zur Erkennung von fehlerhaften Ziehteilen durch Analyse der Systemdaten entwickelt. Zudem werden Versuchsreihen zur Ermittlung der Spezifikation der beim Umformen von Papier und Karton relevanten Materialeigenschaften durchgeführt, welche Anhaltspunkte bei Beschreibung der Versagensursachen geben. Weiterhin erfolgt die Untersuchung der auf den Ziehprozess einflussnehmenden Eigenschaften der Materialfeuchte und -temperatur. Des Weiteren wird ein Modell zur Quantifizierung von Ziehteileigenschaften entwickelt, anhand dessen qualitätsmindernde Eigenschaften reproduzierbar beschrieben werden können. Der Scherpunkt liegt dabei in der Untergliederung von maßgeblichen Eigenschaften in Formhaltigkeit und Faltenbild. / This thesis aims the investigation of the infeed behaviour of card board material during board pressing process. In addition, the material failure, which is defined as the breaking of the architrave of a pressing, will be examined and quantified in detail. The occurrence of material failure is reconstructed and simulated by using analysis system data. The work of friction, which must be executed during the transport of pressing through the implement, is a significant characteristic to describe that process. Based on that specification, an abstract model to detect defectives by monitoring the system data, is developed. Another focus of investigation is the process of an experimental series, developing the specification of the beard material, which is used as foundation to describe the causation of the material breakdown. Furthermore, a model of quantifying pressing qualities is developed focusing subdivision in dimensional accuracy and the quality of the crinkles.

Gegenstand dieser Arbeit ist die Entwicklung eines Verfahrens zum ultraschallunterstützten Ziehen von Karton. Beim Ziehen wird ein Kartonzuschnitt mit einem Stempel durch eine Matrize gezogen und so ein einseitig offener Hohlkörper hergestellt, ähnlich wie beim Tiefziehen von Metall. Die Ziehwerkzeuge sind üblicherweise beheizt, um die Umformeigenschaften des Kartons durch Wärmeeintrag zu verbessern. In dieser Arbeit werden die Werkzeuge jedoch als Ultraschallsonotroden ausgeführt, da beim Metalltiefziehen durch Ultraschallwerkzeuge Verbesserungen der Prozessführung und des Tiefziehteils erreicht wurden. Die Erkenntnisse aus dem Metallbereich können jedoch nicht ohne weitere Forschung übernommen werden. Vor der Entwicklung der Ultraschallwerkzeuge werden in dieser Arbeit daher zunächst Lücken im Stand der Wissenschaft und Technik geschlossen bezüglich der Wirkungen von Ultraschallschwingungen auf Karton. Hierzu wird der Druck im Spalt zwischen den Ziehwerkzeugen ermittelt. Anhand der Druckmessung wird ein Beitrag geleistet zur Ermittlung der Erwärmung von Karton in Kontakt mit Ultraschallsonotroden, der Glättung der Oberfläche von Ziehteilen durch Ultraschall und der Beeinflussung der Stabilität von Ziehteilen durch Ultraschall. Mithilfe dieser Forschungsergebnisse werden die Werkzeugsonotroden ausgelegt und ein Versuchsträger entwickelt, mit dem die Erforschung des Prozesses in einem breiten Parameterraum möglich ist. Die Ergebnisse beim Ziehen mit beiden Werkzeugvarianten werden anhand von Kenngrößen der hergestellten Ziehteile verglichen. Dabei handelt es sich um die maximal erreichbare Ziehteilhöhe, die erreichbare Stabilität gegen axiale Stauchbelastung, die erreichbare Oberflächenrauheit und die erreichbare minimale Formabweichung. Für die Bestimmung der Formabweichung wird auf ein bekanntes Verfahren zurückgegriffen und für die übrigen Kenngrößen werden in dieser Arbeit neue Messverfahren entwickelt. Zusammenfassend lässt sich feststellen, dass mit Ultraschallunterstützung qualitativ hochwertige Formteile herstellbar sind, wobei besonders die erreichbare Oberflächenglätte hervorzuheben ist. / The subject of this work is the development of a process for ultrasonic assisted deep-drawing of cardboard. In deep-drawing, a cardboard blank is drawn through a die with a punch, thus producing a hollow body open on one side, similar to the deep-drawing of metal. The drawing dies are usually heated to improve the forming properties of the cardboard by heat input. In this work, however, the dies are ultrasonic sonotrodes because improvements in process control and drawn part have been achieved in metal deep-drawing using ultrasonic tools. Nevertheless, the knowledge gained in the metal field cannot be adopted without further research. Therefore, prior to the development of ultrasonic tools, this work first closes gaps in the state of science and technology regarding the effects of ultrasonic vibrations on cardboard. For this purpose, the pressure in the gap between the drawing dies is determined. Based on the pressure measurement, statements can be made on the heating of cardboard in contact with ultrasonic sonotrodes, the smoothing of the surface of drawn parts by ultrasound and the influence of ultrasound on the stability of drawn parts. Based on these research results, the tool sonotrodes are designed and a teststand is developed, which allows the process to be explored in a wide parameter space. The results of drawing with both toolvariants are compared on the basis of parameters of the produced drawn parts. These are the maximum achievable drawn part height, the achievable stability against axial compression, the achievable surface roughness and the achievable minimum form deviation. For the determination of the form deviation, a known method is used, and for the other parameters, new measurement methods are developed in this work. In summary, it can be stated that ultrasonic vibrations can be used to produce high-quality molded parts, with particular emphasis on the achievable surface smoothness.

No description available.

The dissertation deals with a suggestion of the production of an oil pan into the car with a deep drawing. The part will be produced out of a deep drawed steel plate – class 11 305 (DC04). On the basis of a calculation and the study of the corresponding literature about the deep drawing a reverse drawing in a convention tools with a blank holder has been suggested. The part of the machine will be also an upper ejector for the fall of a sticking of a drawn part in the die. As a semi-product a blank has been chosen, which is burned out from the piece of plate with the dimension of 2500 x 12500 mm and thickness 1 mm with the help of the laser. The production quantity is 30 000 per one year. As a forming machine a universal hydraulic presser CTH 250 from the Czech company Žďas a.s. with the nominal power 2500 kN has been chosen.

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.

This study focuses on the effects of different constitutive models in sheet metal forming operations by considering the cylindrical and square cup drawing and V-bending simulations. Simulations are performed using eight different constitutive models / elastic plastic constitutive model with isotropic hardening, elastic plastic constitutive model with kinematic hardening, elastic plastic constitutive model with combined hardening, power law isotropic plasticity, piecewise linear isotropic plasticity, Barlatthree-parameter, cyclic elastoplastic and Hill&rsquo / 48 model.The numerical analyses are accomplished by using three different 1 mm thick sheet materials / St12 steel, Al-5182 aluminum and stainless steel 409 Ni. An explicit finite element code is used in the simulations. For square cup drawing, three different blank holder forces / 2 kN, 4 kN and 5 kN are considered for St12 steel, whereas only 5 kN blank holder force is applied for stainless steel 409 Ni and Al-5182 aluminum. A number of experiments are carried out and analytical calculations are utilized to evaluate the results of simulations. In cylindrical cup drawing, simulation results of different constitutive models show good agreement with analytical calculations for thickness strain and effective stress distributions. In square cup drawing, simulation results of all the models displayed good agreement with the experimental results for edge contour comparisons, although the distributions of effective stress vary for different models within the cup. The numerically and experimentally obtained springback amounts are also in good agreement. The simulation results obtained for piecewise linear isotropic plasticity and power law isotropic plasticity models show better agreement with the analytical solutions and experiments.

Sheet metal forming processes, especially deep drawing processes give diverse results by various materials. Extreme differences occur between steel sheets and aluminum sheets. The main causes of this variance are anisotropy, elastic modulus and microscopic material properties. The aim of this thesis is to evaluate the deep drawing properties and also to develop suitable process parameters for aluminum and steel sheets by finite element simulation. In the simulation, the commercial dynamic-explicit code PAM-STAMP has been used. The reliability of the finite element package was verified by a comparison with the NUMISHEET 2002 benchmarks. Additionally, a commercial part is numerically simulated for experimental verification. The results of the simulations have been compared with several experiments that were performed in Metallurgical and Materials Engineering and Mechanical Engineering Departments. Finally, the simulation results are compared with analytical expressions for verification of results. The materials investigated for the deep drawability comparison is a deep drawing quality mild steel and an aluminum alloy designated as 6111-T4. For experimental verification St4 steel is used. Results are in agreement with the fact that aluminum and steel materials behave differently upon deep drawing in terms of the onset of failure, wrinkling and final shape. Aluminum is found to be less formable than steel for cup drawing operations.

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.

In this publication, the ultrasonic-assisted deep-drawing of fiber-based materials, whose implementation was presented in Löwe et al. (2016), was studied in detail. Methods were developed for measuring the properties of deep-drawn cups, including cup stability, shape deviation, and surface quality. The relationship between these properties and the process parameters were determined with a design of experiment, which allows the user to adjust the cup properties in order to optimize them.

Made available in DSpace on 2016-12-08T17:19:33Z (GMT). No. of bitstreams: 1 Capa.pdf: 100296 bytes, checksum: 85da33d7d5aa32b41734416b7ba82f1a (MD5) Previous issue date: 2009-09-16 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Numerical simulation of metal forming processes requires a constitutive model, which depends upon adequate material parameters. A direct determination of material parameters usually admits homogeneous stress and strain states in the specimen, thereby narrowing the application range to moderate deformations or even compromising accuracy in some industrial applications. Therefore, a combined experimental and numerical technique based on optimisation strategies is recommended. Such method is generally known as parameter identification and produces stress states close to those to be verified in industrial operations. In this work, a parameter identification technique based upon deep drawing experiments is presented. Sensitivity analysis is performed using a modified finite difference method, and the optimization itself is developed using quadratic programming. Sensitivity results using the classical and the modified finite difference methods are studied and compared, especially with respect to the application of automatic or imposed step increments. It is observed that the modified method yields a more effective behaviour with respect to the automatic time step strategy, allowing use of a wider range of penalization factors and attaining greater efficiency. Several identification problems are presented showing qualitative agreement with related research in the literature. Difficulties arise in the simultaneous determination of multiple material parameters, due to typical flat regions or to the presence of local minima in the design space, suggesting future combination of the presented approach with evolutionary algorithms. / Toda simulação numérica de um processo de conformação mecânica requer um modelo constitutivo, que depende de parâmetros materiais adequados. Muitas vezes a determinação direta dos parâmetros materiais admite um estado homogêneo de tensão e deformação no corpo de prova, provocando um estreitamento na sua faixa de aplicação as situações onde ocorrem deformações moderadas ou então comprometendo a precisão dos resultados em algumas aplicações industriais. Portanto, uma combinação entre as técnicas numérica e experimental utilizando técnicas de otimização é recomendada. Esta estratégia é geralmente conhecida como identificação de parâmetros e produz estados de tensão próximos ao verificado nas operações industriais. Neste trabalho é apresentada a técnica de identificação de parâmetros baseado num processo de estampagem profunda. A análise de sensibilidade é avaliada utilizando um método de diferenças finitas modificado e o processo de otimização utiliza programação quadrática seqüencial. Estudam-se os resultados de análise de sensibilidade utilizando os métodos de diferenças finitas tradicional e modificado, sujeitos a incrementos de tempo automático e imposto. Observa-se que a aplicação do método modificado fornece maior eficácia na aplicação da estratégia de incremento de tempo automática, além de permitir o uso de uma faixa mais ampla de fatores de penalização para o contato e de resultar em maior eficiência numérica. Vários problemas de identificação são apresentados, mostrando concordância qualitativa com os resultados disponíveis em publicações da literatura correlata. Dificuldades são encontradas na determinação simultânea de vários parâmetros devido à presença de regiões planas ou de mínimos locais no espaço de projeto, sugerindo a futura combinação da abordagem proposta neste trabalho com algoritmos evolucionários.