Analysis of startup behavior in a "C-shaped" armature using linked EMAP3D/DYNA3D finite element codes

An important consideration in the design of solid armatures is whether they maintain good solid-on-solid sliding contact during the initial portion of a launch, when the magnetic pressure is too low to provide sufficient loading of the contact faces. This paper analyzes the complete electrical/structure startup behavior of a "C-shaped" armature in the 40 mm, square bore, laboratory launcher at the IAT, using a pair of linked 3D finite element codes. A first analysis solves for the electromagnetic loading on conductors using the EM code EMAP3D. A second analysis uses the hydrocode DYNA3D to solve the dynamic response of the armature, rails, insulators, and railgun containment using the results from EMAP3D as forcing functions. Peak displacements transverse to the direction of motion are found to be in the order of 0.1 mm.