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Jager A.,Institute of Forming Technology and Lightweight Construction | Risch D.,Institute of Forming Technology and Lightweight Construction | Tekkaya A.E.,Institute of Forming Technology and Lightweight Construction
Journal of Materials Processing Technology | Year: 2011

In this paper, a strategy for the thermo-mechanical processing of aluminum profiles by subsequent electromagnetic forming and heat treatment is given. A tool coil for electromagnetic compression was positioned behind the die exit and coaxially to the extrudate in order to reduce the workpiece cross section locally. Additionally, a counter die in the shape of a mandrel was mounted to the mandrel of a porthole extrusion die which extended into the tool coil. Besides achieving a more defined geometry in comparison to a free forming operation, by this also the geometrical complexity of locally compressed areas can be achieved. © 2010 Elsevier B.V. All rights reserved. Source


Tekkaya A.E.,Institute of Forming Technology and Lightweight Construction | Hussain M.M.,Institute of Forming Technology and Lightweight Construction | Witulski J.,Institute of Forming Technology and Lightweight Construction
Production Engineering | Year: 2012

The polymer injection forming process is a recent invention for producing plastic-metal hybrids. It is a combination of injection molding and sheet metal hydroforming process in which polymer melt serves as a pressure medium. This paper presents the experimental investigations on the non-Newtonian nature of thermoplastic melt as pressure medium. The objective of this work is to identify the presence of non-hydrostatic pressure distribution within the cavity and its influence on the final shape of the formed sheet metal component. Experiments are conducted with center-gated injection mold under varying processing conditions. The development of localized cavity pressure during the process is recorded and evaluated against the final shape of formed sheet metal. It has been observed that higher injection rate, higher injection temperature, and higher melt flow index of the processed polymer is necessary for the uniform pressure distribution and subsequently uniform forming of the sheet metal. © 2012 German Academic Society for Production Engineering (WGP). Source


Tekkaya A.E.,Institute of Forming Technology and Lightweight Construction | Trompeter M.,Institute of Forming Technology and Lightweight Construction | Pham H.-D.,Institute of Forming Technology and Lightweight Construction
Production Engineering | Year: 2010

Organic coated sheet metals (OCSM) are widely used in many industrial applications such as the automobile industry or in electrical appliances because of their high corrosion resistance and satisfaction of ecological requirements. However, original functions of the very thin coating layer in OCSM products may change during forming, which leads to a reduction of the product's quality. This paper deals with the reduction of the gloss property of OCSM products. To this end, first a forming limit diagram (FLD) and a fracture limit diagram of the coating layer (FLDC) of OCSM are established by using Nakajima tests. Subsequently, the Nakajima tests are performed at a predefined strain in order to evaluate the change of the gloss property depending on the strain states. The loss of gloss as a function of plastic strain is used as a reference. For the verification of this reference, deep-drawing tests are carried out and the change of the gloss property on the surface is analyzed. The obtained results are in good agreement with the reference, so it can be applied for process design to predict the gloss reduction of OCSM products. © 2010 German Academic Society for Production Engineering (WGP). Source


Mennecart T.,Institute of Forming Technology and Lightweight Construction | Guner A.,Institute of Forming Technology and Lightweight Construction | Khalifa N.B.,Institute of Forming Technology and Lightweight Construction | Tekkaya A.E.,Institute of Forming Technology and Lightweight Construction
Key Engineering Materials | Year: 2014

Due to the increase of lightweight design in car bodies, there is a raise in use of tailored welded blanks (TWB). With these blanks it is possible to strengthen the car body where it is necessary. This can lead to less weight. In the case of TWB, there is a weld line, which influences the deep drawing behavior significantly during forming. In the presented results two different high strength steels (HCT980X and HCT600X) are welded together. One forming operation is performed, in which the weld line is positioned differently. The results show the influence of the weld line on the forming behavior which is realized by the comparison of deep drawn monolithic parts with the deep drawn tailored welded blanks. While the monolithic parts could be formed without failure, the forming of tailored welded blanks was accompanied by cracks in dependency to the weld line orientation and the applied load in this region. The results also show that the failure occurs in the base material and that the weld line is not damaged by the applied load. After the characterization of the base materials and the weld material, a numerical modelling of the whole TWB could be realized in this work. Two different ways of modelling techniques of the weld line are compared and the necessity of the consideration of the weld line properties is demonstrated. Furthermore, in consideration of the weld line properties in the FE-Model, it is possible to show that the weld line resists the forming operation without failure. © 2014 Trans Tech Publications, Switzerland. Source

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