Calculation and verification of lateral and pinch electromagnetic action on the shaped charge jet in the passive electromagnetic armor

To improve the armor´s defense ability, the lateral and pinched electromagnetic forces are studied when shaped charge jet is penetrating through the passive electromagnetic armor. Based on the equivalent circuit model, the paper proposed a mechanical model of the lateral and pinched forces from shaped charge jet to study the variations of the lateral electromagnetic force with time and locations. The virtual origin concept is integrated to establish the lateral displacement velocity model of the shaped charge jet after its penetration through the two armor plates, only to find that almost half length of the shaped charge jet experienced effective displacement when the capacitor´s voltage reached 35 kV. Based on the same equivalent circuit model, this study proposed the theoretical formula of surface electromagnetic pressure which is equivalent to the electromagnetic volume force, and analyzed the decay of the equal-effect surface electromagnetic pressure (EESEP) concussively with time. By analyzing the threshold phenomena of averaged EESEP, it also addressed the influence of the ratio of the shaped charge jet radius to skin depth (ř) on the threshold phenomenon. Results showed that, the averaged EESEP would increase rapidly with decreasing ř when ř<;1. Numerical simulation and theoretical results indicated that, the sausage instability would occur when the averaged EESEP increases rapidly in the smaller parts of the shaped charge jet with relevant parameters properly selected. Experiment with the 5kV passive electromagnetic armor found that, when affected by the lateral and pinch electromagnetic force, obvious displacement would occur to the shaped charge jet left in the aftereffect target. The experiment also found that, the penetration diameter of the shaped charge jet in the aftereffect target is obviously larger than that without voltage.