Wspólnotowy Serwis Informacyjny Badan i Rozwoju - CORDIS

FP5

EMF Streszczenie raportu

Project ID: G3RD-CT-2002-00798
Źródło dofinansowania: FP5-GROWTH
Kraj: Switzerland

Report on influence of material and process parameters on part quality

An important precondition for the valuation and optimization of the electromagnetic preforming operation is the knowledge of significant process parameters and their influence on the forming process as well as on the forming result.

In the project, two different kinds of the EM-forming process are investigated: the compression of tubular workpieces and the forming of sheet metal.

The investigation of the EM-compression of tubular workpieces is carried out assuming that it is one production step in the process chain bending - electromagnetic compression hydroforming. This means that the final product of the electromagnetic compression is the semi-finished part for the hydroforming process.

This has to be considered for the choice of material and process parameters.
By considering the pressure course and its distribution, which affect the load on the workpiece, the influence of tool coil and characteristics of the forming machine are excluded. The pressure course and its distribution give rise to reactions on the tube in terms of radial deformation and deformation velocity, which affect the final geometric properties.

For the tube compression process the following process parameters have been defined and their correlations and interactions have been investigated:
- Current pulse
- Pressure course characterized by pressure maximum and pressure rise time
- Pressure distribution
- Radial deformation
- Forming velocity/ strain rate
- Geometric properties characterized by roundness and contour and for the sequential forming using sequential forming steps additionally
- Movement of the tube relative to the tool coil between two forming steps

The current pulse is one important aspect affecting the process. It is influenced by properties of the tool coil, the forming machine, and the charging energy of the capacitor battery. To achieve a good efficiency coefficient of the process, the frequency of the current pulse has to be optimized by adjusting the tool coil parameters to the forming machine.

The pressure course directly depends on the current pulse and directly influences the forming velocity. The pressure course can be characterized by its maximum and duration, both influencing the achievable tangential strain in a free forming operation, as well as the pressure rise time, which significantly influences the forming velocity.
The pressure distribution over the axis of the tube significantly influences the contour of the tube, this means the shape along the z- coordinate. It can be adjusted by the design of the tool coil and an additional tool element called fieldshaper.

As mentioned, in a free forming process the radial deformation of the workpiece is determined by the pressure maximum and its duration. With an increasing tangential strain the resulting roundness of the workpiece decreases. This effect can be reduced by increasing the forming velocity.

The maximum length which can be compressed during one single forming step is limited. A possible solution for the compression of even longer areas of the tube is offered by the sequential forming. Thereby, during each forming step a tube compression process is being performed and than the workpiece is moved in axial direction relative to the tool coil.

The electromagnetic sheet metal forming can beneficially be used as a calibrating operation for small areas in deep drawing parts. Before performing a forming process with a die it was necessary to investigate the free forming process to obtain process fundamentals and a clear understanding of the process.

As a result of the performed investigations and several discussions between the project partners the following process parameters have been defined:
- Current impulse
- Pressure impulse defined by pressure maximum and duration of the pressure impulse
- Pressure distribution
- Workpiece deformation
- Forming velocity

Analogous to the tube compression process, also for sheet metal forming the current pulse is influenced by properties of the tool coil, the forming machine, and the charging energy of the capacitor battery and has to be optimized by adjusting the tool coil parameters to the forming machine.

In contrast to the tube compression process the pressure course is significantly influenced by the workpiece deformation and cannot be calculated analytically. Furthermore, there is no direct influence of the pressure rise time on the forming velocity.

The pressure distribution can be adjusted by the design of the tool coil and it significantly influences the forming velocity and its distribution.

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Reported by

ALCAN TECHNOLOGY & MANAGEMENT AG
16 Badische Bahnhofstrasse 16
8212 NEUHAUSEN AM RHEINFALL
Switzerland
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