New forming limits for light alloys by means of electromagnetic forming and numerical simulation of the process

It is well known that one of the main advantages of the high speed forming (HSF) processes is the improvement in the forming limits of the used materials. Using the Electromagnetic Forming (EMF) technology two materials have been tested with different mechanical and physical properties: the AA5754 aluminium and the AZ31B magnesium alloys. The EMF process principle can be described as follows: A significant amount of electrical energy is stored in a bank of capacitors which are suddenly discharged releasing all the stored energy. This electric discharge runs through a coil which generates an intense transient magnetic field. At the same time transient Eddy currents are induced in the electrically conductive part placed some millimetres far from the coil. Another intense magnetic field is generated due to those Eddy currents but on the opposite direction as the one generated by the coil.A big magnetic repulsion force is created between the part and the coil. This magnetic repulsion between both fields is used to launch the blank with no physical contact and obtain the desired deformation on it. The Forming Limit Diagrams (FLD) obtained in the EMF experiments were them compared to the ones obtained with the "Nakazima" method at conventional deformation speed for both alloys. In parallel to these physical experiments, some simulations were carried out. But trying to simulate this process by FEM is a though work. There are several physics and many factors to take into account in a few microseconds deformation process. And all these factors are tightly related with each other, that is why to this date there is no commercial software able to simulate the EMF process accurately. From LABEIN-Tecnalia we are working with to different softwares to simulate the whole process: Maxwell 3D ® for the electromagnetic part and PAM-STAMP2G ® for the mechanical part of the problem.