Dependence of electromagnetic force on rib geometry in the electromagnetic forming of stiffened panels

The electromagnetic force is the key factor affecting the electromagnetic forming (EMF) process of integrally stiffened panels. In this work, the influence of rib distribution and height on the distribution and variation rules of electromagnetic force in the EMF of stiffened panels is analyzed via the finite element simulation. The results show that the distributions and peaks of electromagnetic forces on the no-rib panel, panel with X direction ribs, panel with Y direction ribs, and grid-rib panel are very different. The electromagnetic force on the stiffened panels distributes irregularly and concentrates on the ribs because of the skin effect of the eddy. The grid-rib panel presents larger peak force than the other two panels with single direction ribs and the panel without ribs, which may due to the more efficient restraint of the magnetic leakage. However, the maximal forces on the webs of the four panels are very close. With the increase of the rib height, the maximal values of the normal and the horizontal electromagnetic forces both increase rapidly, and the ratio of the horizontal force to the normal force firstly increases and then tends to a certain value. Both the simulated result and verification experiment show that when the rib height increases to 12 mm, the horizontal electromagnetic force would cause obviously transversal bend for the ribs along the X direction; thus, its effect on deformation cannot be ignored.