iv Sheet metal forming technologies are challenged especially by the improvements in the automotive industry in the last decades. To fulfill the customer expectations, safety requirements and market competitions, new production technologies have been implemented. This study focuses on the assessment of conventional and new sheet metal forming technologies by performing a systematic analysis. A geometry spectrum consisting of six different circular, elliptic, quad cross-sections are selected for the assessment of conventional deep drawing, hydro-mechanical deep drawing and high-pressure sheet metal forming. Within each cross-section, three different equivalent drawing ratios are used as a variant. More than 200 numerical experiments are performed to predict the forming limits of three competing processes. St14 stainless steel is used as the material throughout the assessment study. The deformation behavior is described by an elasto-plastic material model and all numerical simulations are carried out by using dynamic-explicit commercial The process validation is done by interpreting the strain results of numerical experiment. Therefore, the reliability of predictions in the assessment study highly depends on the quality of simulations. The precision of numerical experiments are verified by comparing to NUMISHEET benchmarks, analytical formulation, and experiments to increase the assets of the assessment study. The analyses revealed that depending on the workpiece geometry and dimensional properties certain processes are more preferable for obtaining satisfactory products. The process limits for each process are established based on the analyzed crosssections of the spectrum. This data is expected to be useful for predicting the formability limits and for selecting the appropriate production process according to a given workpiece geometry.Dynamic-explicit FEM, Deep drawing, Hydroforming, Forming limits, Process evaluation

Recycling of plastics always plays an important role in keeping our environment better and safe. With the rise in usage of plastics and industrialization, the need for recycling the plastics has become a big business and is getting bigger. This thesis work was done for a company called Rapid Granulator AB, which works with the recycling of plastics as a big trade in Sweden. Like all the industries across the globe are trying to be economical in every way, Rapid Granulator AB wanted to develop an economical design of their high quality granulating knife. For achieving the economical design, they wanted to study the behaviour of the rotating knife during the process of producing plastic granules. The granulator cutting process was simulated and numerical analysis was done on the rotating knife of a plastic granulator machine by using the finite element code ABAQUS with 3D stress elements to find out the critical stresses and forces acting on the rotating knife. The bolt preload was applied by Abaqus/Standard, and the results of implicit analysis were imported to Abaqus/Explicit for the impact analysis where the flow of stresses on the rotating knife during the impact with materials were simulated and studied. The study was done on knife models of different thickness to see if the thickness of the current knife model can be reduced. Analysis were done also on a knife model assembly with a double sided cutting edge knife to see if the knife model can be used to its full extent. The simulation models and analysis results were given to the company to develop a more economical knife model.

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.

A park lock is a mechanism used to prevent unintentional movement of the vehicle. A failure in the proper function of this mechanism can lead to the safety concerns of an automobile. The main focus of this thesis is to understand the reason behind the failure of the park lock mechanism by FEM analysis in ANSA. For this, temperature build up during the park lock engagement has been studied in a dynamic explicit analysis. The FE results are compared to results from experiments on park lock. The modelling has been done in ANSA, ABAQUS was used as a solver for simulation and the results have been studied in META. The results indicate that there is a rise in the temperature. This is due to the friction between the contact surfaces and the oscillations generated in the vehicle. Based on the observations, discussions and conclusions are formulated and the research questions are answered.

1. Scope of the Study<BR> ---------------------<BR> In the modern engineering world, technological advancements drive the product design process. Increasingly powerful CAD programs make more complex product designs possible, which in turn boost the demand for more complex prototypes. At the same time, fast-moving competitive markets require frequent design changes, shorter lead times, and tighter budgets. In short, prototyping must be faster, better, and less expensive.<BR> <BR> Within this context, rapid prototyping in sheet metal is highly desirable because the manufacturing of functional prototypes speeds up the time to market. While the market is well developed when it comes to rapid prototyping for plastic parts, the options for prototyping geometrically complicated sheet metal components are more limited and extremely expensive, because all the methods available require expensive tooling, machinery or manual labor.<BR> <BR> Unlike many other sheet metal forming processes, incremental forming does not require any dedicated dies or punches to form a complex shape. Instead, the process uses a standard smooth-end tool, the diameter of which is far smaller than the part being made, mounted on a three-axis CNC milling machine.<BR> <BR> The sheet metal blank is clamped around its edges using a blank-holder. During the forming process, the tool moves along a succession of contours, which follow the final geometry of the part, and deforms the sheet into its desired shape incrementally.<BR> <BR> 2. Context of the Research<BR> --------------------------<BR> The work presented in this thesis was started in October 2003 in the framework of the SeMPeR project (Sheet Metal oriented Prototyping and Rapid manufacturing). This was a four-year-long project, whose purpose was to develop a research platform that would support an in-depth analysis of the incremental forming and laser forming processes. This platform supported experimental, numerical, and analytical research activities, the interaction between which was expected to lead to the design of new and improved process variants and the identification of effective process planning and control strategies.<BR> <BR> Four research partners from three different universities were involved in the project, covering the various academic disciplines required. As project leader, the PMA Department of the Catholic University of Leuven (KUL) provided extensive background knowledge in numerically controlled sheet metal forming processes, as well as long-term experience of experimental hardware development and process planning. This department was in charge of the experimental study of the processes. The MTM Department from the same university studied the processes in detail using accurate finite element models. The MEMC Department of the Free University of Brussels (VUB) provided expertise in in-process strain and displacement measurement, and material characterization by means of inverse method techniques. Finally, the ArGEnCo Department of the University of Liège (ULg), to which the present author is affiliated, undertook the task of developing a finite element code adapted to the incremental forming process.<BR> <BR> Because of its promising outcome, the project held wide industrial interest: several companies assisted in ensuring the ultimate industrial relevance of the research and provided logistical support in terms of hardware, materials, and specific data.<BR> <BR> 3. Objective of the Thesis<BR> --------------------------<BR> Although the SeMPeR project aimed at studying two rapid prototyping processes, the present work focused only on one of those: incremental forming. The goal of the team at the University of Liège was to adapt a department-made finite element code, Lagamine, to the incremental forming process. In particular, the computation time had to be reduced as much as possible while maintaining a sufficient level of accuracy.<BR> <BR> 4. Outline of the Thesis<BR> ------------------------<BR> The body of the text is divided into three parts.<BR> <BR> The first part contains two chapters. The first of these provides a literature review in the field of incremental forming. More specifically, it introduces the process, presents an overview of its practical implementation and experimental setup requirements, and shows its benefits and limitations. Then, the chapter focuses on the latest developments in terms of finite element modeling and analytical computations.<BR> <BR> The second chapter presents the numerical tools used throughout this research. This consists mainly of the finite element code, the elements, and the constitutive laws. Then, this chapter gives an overview of the experimental setup and measuring devices used during the experimental tests performed in Leuven. The second part focuses on dynamic explicit simulations of incremental forming and contains four chapters. The first justifies the use of a dynamic explicit strategy. The second presents the new features added to the finite element code in order to be able to model incremental forming with such a strategy. The third explains the computation of the mass matrix of the shell element used throughout this part of the thesis and justifies this computation. Finally, the fourth chapter analyzes the overall performance of the dynamic explicit simulations both in terms of accuracy and computation time.<BR> <BR> The third part of this thesis contains an in-depth analysis of the incremental forming process using more classic implicit finite element simulations. This analysis is performed in two steps. In a first chapter, the influence of using a partial mesh for the simulations is evaluated in terms of accuracy and computation time. Then, in a second and final chapter, a detailed analysis of the deformation mechanism occurring during this forming process is carried out.<BR> <BR> Finally, this thesis ends with the major conclusions drawn from the research and perspectives on possible means of further improving the simulation tool.<BR> <BR> 5. Original Contributions<BR> -------------------------<BR> Through this research, several major contributions were achieved.<BR> <BR> First, a comprehensive literature review of the incremental forming process was carried out. In particular, the review focused on original articles concerning the limitations of the process and possible ways of bypassing them; on the most recent explanations for the increased formability observed during the process; and on the state of the art in finite element simulations of incremental forming. Understanding the concepts and difficulties inherent in these publications was made possible particularly by the SeMPeR project thanks to the discussions held and the monthly follow-ups on research performed by its members.<BR> <BR> Secondly, Lagamine's shell element was corrected and its mass matrix modified to enable its use with an explicit strategy. Following this, a new approach for modeling the contact between an element and the forming tool during simulations in a dynamic explicit strategy was developed and thoroughly tested. A detailed comparison of the influence of various finite element parameters on the simulations' results was performed, in particular regarding the choice between using the implicit and explicit strategies and the use of mass scaling to reduce the computation time.<BR> <BR> In addition, many simulations were validated thanks to experimental results.<BR> <BR> Moreover, the computation time required for simulations of the forming of parts with rotational symmetry was radically reduced by using a partial model with a new type of boundary conditions.<BR> <BR> Finally, the material behavior occurring during incremental forming was analyzed.