Search

A new process combining incremental sheet forming and the use of an active medium to produce concave-convex geometrical parts is introduced. Both, experiments and finite element modeling, pursue the objective of explaining the basic forming mechanism and of discussing the influence of the active medium pressure on the overall process feasibility. Results show that the active medium, in this case gas, acts as an active supplementary tool under controlled pressure, thus enabling the manufacture of concave–convex parts which could not be easily produced by conventional incremental sheet forming.

Finite elemente analysis (FEA) allows to reduce development time during the die design stage as well as costly extrusion trials with prototypes. Therefore, it is essential that FEA computation provides reliable results. Among other output quantities such as temperature, load, or die stress, the prediction of material flow is one of the most essential ones. Especially in porthole dies, the material flow can be very complex and thus the position of the seam welds in the profile may be uncertain. In this study the particle tracing method was utilized to determine and finally adjust the seam weld positions in a double hollow profile with varying wall thicknesses over the cross section. The seam weld positions resulting from the original die design were determined by Eulerian FEA computation in the first step. Subsequently, the seam weld positions were adjusted by changing the die geometry. The simulation results were verified by means of extrusion tests, which were conducted under industrial conditions. In addition, Lagrangian and Eulerian FEA was utilized to analyze the evolution of the seam weld positions by evaluation of material flow as well as pressure distribution during the transient initial stage and the steady-state stage of the extrusion process. It was demonstrated that steady state process simulation and the particle tracing method can be used for the prediction of seam weld positions in complex hollow cross sections.

During electromagnetic forming, excessive bending of the specimen takes place due to high velocities and inertia. We show that the excessive bending can be prevented by optimizing the coil geometry in case of uniaxial tension. The process is simulated with various coil geometries, and the resulting amount of bending is compared to the case of standard Nakajima Test. The comparison shows that the bending can be minimised to acceptable levels to be able to call the method a decent way of determining forming limits. The results should be verified experimentally.

The incremental procedure of sheet-bulk metal forming was classified into two different forming sequences, the discrete and the continuous. Based on these two groups, a movement matrix was developed, which captures required kinematic motions to manufacture a variety of functional components. With the objective of producing near-net-shape workpiece geometries within the Collaborative Research Centre TR73 - sheet-bulk metal forming, the required positioning accuracies of conventional metal forming machines exceed the current state of the art. Therefore, a suitable machine concept was developed and realized. This new machine represents a unique prototype for a flexible application of bulk forming operations to 2 - 3 mm sheets with five motion axes. During continuous forming, such as rolling, and also during simultaneous operations, increased lateral forces prevail. The machine was provided with a high stiffness. That enables a positioning accuracy which, also under load and at rest, correlates the high demands of the sheetbulk metal forming within a range of ±0.01 mm.

The accurate simulation and the optimization of extrusion processes can be a helpful technique to ensure producibility of complex aluminum profiles, for example for the automobile industry. Currently, the die designing is based on expert's knowledge and cost-intensive prototyping. The paper deals with numerical investigations based on finite element simulations as well as experimental investigations of an industrial extrusion process. A newly developed method for longitudinal seam weld prediction is applied to analyze the position of the longitudinal welding line and the welding quality.

Three innovative extrusion processes are presented: Extrusion of profiles with variable shapes, 3D curved profile extrusion for the manufacture of profiles with complex contours, and helical profile extrusion for the manufacture of twisted profiles. All these processes are based on influencing the material flow inside and behind the extrusion die. These procedures profit from the fact that only a very low load is needed to deflect the material flow in order to produce complex variable geometries. The results of experimental as well as numerical investigations are presented. The process limits and examples of extruded parts are also shown. © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The 4th International Conference on Extrusion and Benchmark (ICEB 2011) will be held in Bologna, Italy from October 3-5, 2011. A large number of extruders, die makers, software houses, and researchers will gather at the event to discuss the core technology of light metal extrusion. More than 50 abstracts have been accepted on light alloy extrusion processing and the first day will be dedicated to these sessions. Papers will be also presented on ultra light alloys and new applications for extruded profiles. Process optimization and solutions to extrusion related issues will be analyzed thoroughly by several contributors. The second day of the event will be mainly dedicated to the benchmark experiment and participant results where the results of two monitored experiments will be discussed. The Scientific Benchmark will focus on the different strategies for balancing the material flow in porthole dies and its die design will deal with issues of hollow profile production, such as seam welding mechanism and material flow. The 4th International Conference on Extrusion and Benchmark (ICEB 2011) will be held in Bologna, Italy from October 3-5, 2011. A large number of extruders, die makers, software houses, and researchers will gather at the event to discuss the core technology of light metal extrusion. More than 50 abstracts have been accepted on light alloy extrusion processing and the first day will be dedicated to these sessions. Papers will be also presented on ultra light alloys and new applications for extruded profiles. Process optimization and solutions to extrusion related issues will be analyzed thoroughly by several contributors. The second day of the event will be mainly dedicated to the benchmark experiment and participant results where the results of two monitored experiments will be discussed. The Scientific Benchmark will focus on the different strategies for balancing the material flow in porthole dies and its die design will deal with issues of hollow profile production, such as seam welding mechanism and material flow.

In contrast to conventional extrusion processes, where a lot of research is done on in the welding quality, in composite extrusion, research is investigated into the welding line positioning. As a result of the process principle, the reinforcing elements are embedded into the longitudinal welding line. Hence, an undefined material flow inside the welding chamber induces reinforcement deflection, which can lead to reduced mechanical properties, as momentum of inertia. Therefore and to reduce costly experimental investigations, a new method of an automated numerical welding line prediction was developed. The results form HyperXtrude finite element calculations are used for special particle tracing simulations to predict the welding line in the profile cross section accurately. The procedures of segmentation and characteristic extraction are presented to approximate the welding line by cubic spline functions. The method was fully programmed in the Java program language, and works well for all HyperXtrude process models consisting of tetrahedral elements.

A method for the numerical estimation of the final hardness distribution of heat treated aluminum alloys was developed and implemented into a commercial finite element (FE) tool. Jominy end-quench tests were carried out in order to determine the quench sensitivity of the aluminum alloy EN AW-6082. The hardness distribution of the alloy after end-quenching was related to the corresponding cooling rates. The derived relation was tested for an industrial application by investigating the local heat treatment of a prototype crash absorbing structure. Numerical estimations were validated with experimental measurements. Effectiveness of the derived method and possible improvements were discussed.

The current investigation is concerned with the grain structure evolution in an Al-Zn alloy (EN AW-7020) during the hot forward extrusion process. In order to analyze that, a miniature hot forward extrusion setup was designed which allows the quenching of the extrusion butt immediately after extrusion. In order to gain a better understanding of the process, the shape of the deformed grains was analyzed and the process was simulated. The shape of these grains was indentified in two directions in the different grain zones, e.g. dead metal zone and shear zone. The FE simulations showing the different grain zones were also illustrated. Simulation results and the micrographs were quite promising to find parameters for simulation models in order to predict grain sizes with the method presented in the current research work.