Mechanical analysis of the dynamic structural instability of sheets during electromagnetic forming process

In order to reveal the plastic instability mechanism of sheets during electromagnetic forming (EMF), the dynamic structural response of blank undergoing pulsed magnetic forces was analyzed on the bases of the dynamic plastic deformation characteristics of EMF upon establishing the typical dynamic magnetic tensile experiments. Mechanical analysis results show that inertia force plays an important role in dynamic forming, which results in two typical deformation stages, the pulsed magnetic force affecting stage and the inertial motion stage, successively. The involved dynamic deformation modes accord with the law that the initial plastic deformation associated with the absorption of kinetic energy and the latter plastic deformation produced from the dissipation of the kinetic energy. And the presence of inertia force makes the blank exhibit the characteristic of self-inhibition of its own structural instability, which is helpful to spreading deformation instability and to improving the formability of sheets.