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.

The design as well as the subsequent analysis of a deep drawing and in-process electromagnetic sheet metal forming calibration will be described in this paper. Due to the quite different forming processes concerning the occurred strain rates, an investigation on the microstructure of the formed workpieces will be pointed out. Furthermore, the design steps regarding the integrated tool coil will be presented and the resulting examples discussed. Finally, the setup of the integrated process as well as the feasibility will be shown on an exemplary semi-industrial workpiece.

Electromagnetic forming is an impulse or high-speed forming technology using pulsed magnetic field to apply Lorentz' forces to workpieces preferably made of a highly electrically conductive material without mechanical contact and without a working medium. Thus hollow profiles can be compressed or expanded and flat or three-dimensionally preformed sheet metal can be shaped and joined as well as cutting operations can be performed. Due to extremely high velocities and strain rates in comparison to conventional quasistatic processes, forming limits can be extended for several materials. In this article, the state of the art of electromagnetic forming is reviewed considering:. basic research work regarding the process principle, significant parameters on the acting loads, the resulting workpiece deformation, and their interactions, and the energy transfer during the process:. application-oriented research work and applications in the field of forming, joining, cutting, and process combinations including electromagnetic forming incorporated into conventional forming technologies.Moreover, research on the material behavior at the process specific high strain rates and on the equipment applied for electromagnetic forming is regarded. On the basis of this survey it is described why electromagnetic forming has not been widely initiated in industrial manufacturing processes up to now. Fields and topics where further research is required are identified and prospects for future industrial implementation of the process are given. (C) 2010 Elsevier B.V. All rights reserved.

A drop-weight high-speed tensile testing instrument was developed, in which the acting force and the specimen elongation can be obtained by measuring the displacement of the drop-weight by means of an opto-electronic transducer. The system was used to obtain the flow curves of AA5754 at strain rates up to 2,200 s−1. The flow curves were verified with the help of finite element calculations by comparing the displacement and full-field strain measurement results. The developed instrument provides satisfying flow curves, in addition to being simple and cheap.

Due to the high forming velocities during electromagnetic sheet metal forming processes, a high impact force acts between workpiece and die. Here, the die surface sustains high damages shown by high wear and galling of the workpiece on the die surface. To enhance the die lifetime, a novel coating concept based on the PVD (physical vapour deposition) process was developed. In doing so, the hardness and the toughness of the designed layers were varied and adjusted to the demands of AlMg-sheet forming process.

Three high speed tensile tests of the aluminum alloy AlMg3 and finite element (FE) simula-tions of these tests were performed. The strain rate dependency parameters for the Cowper-Symonds material model, which minimize the difference between measured and simulated displacement results, were deter-mined. The verification of the determined parameters by means of strain distribution comparisons between an additional experiment and its simulation revealed the necessity for further consideration of the parameters.

Within the electromagnetic sheet metal forming process, workpiece velocities of more than 300m/s can occur, causing typical effects when forming into a die, which will be described and discussed in the present paper. These effects make numerous demands regarding the die design. In order to analyze these requirements, experimental as well as numerical investigations have been carried out. Thereby, special focus is put on the possibilities to accomplish these requirements, which are discussed in the following.

The electromagnetic forming (EMF) is a process for forming sheet metals or thin metal tubes with a high electrical conductivity such as Al-alloys. Extremely high forming velocities can be achieved by employing this process based on pulsed electro-magnetic fields. To exploit the advantages of this process in forming sheet materials with a limited electrical conductivity thermal spraying methods have been applied. The essential requirement is based on the design and development of an electrically conductive layer system, which can act as a “driver“ for materials to be formed. Therefore, the layer has to fulfil high demands on its density as well as on the adhesion to the substrate. In this contribution a new coating concept for thin sheets to be electromagnetically formed is presented. The influences of pre-cleaning processes, coating parameters, layer properties and sheet thickness on the deformation are scrutinized. Accompanying metallographic, mechanical and microscopic investigations of the coated layers help to understand the mechanisms of materials behaviour during EMF processes.

Over the past few years, various papers have been published in the field of high speed forming processes. The focus was mainly on the technological aspects of metal forming, however. Therefore, the present contribution puts an emphasis on transmission electron microscopy analyses. The present research work describes the effects of the two forming processes upon the aluminum microstructure and their influence on the material properties. The objective is to characterise the micro processes determining the plastic deformation with both forming velocities – the electromagnetic high speed forming process with strain rates of 10,000 s and the bulge test, having deformation rates of less than 0.1 s as a quasistatic process. In this article sheet metals out of technical pure aluminum 99.5% with a thickness of 1 mm were investigated. To this end, sample specimens were taken from manufactured workpieces along the radius at various distances from the center. Because of the similarity of the forming paths, two places on the specimens manufactured at different forming rates were evaluated and compared to each other: immediately next to the blankholder and from the area of maximum strain. Metallographic tests of the structures, the sheet thickness, and the micro hardness distribution of the initial state and the formed sheet metals were executed in advance.

Electromagnetic forming is a high-speed process using pulsed magnetic fields to apply a magnetic pressure to the workpiece surface. In order to guarantee a high durability of the tool, an innovative hybrid material design has been developed, which benefits from a functional separation. Thereby, a copper layer of high electri- cal conductivity has been deposited on a substrate made of steel. For the deposi- tion, the arc spraying process was employed. Novel air nozzles have been designed to focus the air jet. These nozzles have been compared to commercially available nozzles regarding the spraying jet and coating quality. Additional heat-treatment has been investigated to achieve a high electrical conductivity. The feasibility of this concept was proved and first design aspects are investigated using experimental and numerical methods.