Coupled finite-element codes for armature design

This paper discusses the development of a design tool that couples two-dimensional (2-D) electromagnetics (EM) with three-dimensional (3-D) dynamic structural mechanics. The resulting model has the capability for rapid performance assessment of railgun and armature structures. The coupling of codes is one-way in that no deformations are provided to the EM code once the calculations begin. An efficient and accurate 2-D EM code is used to generate the thermal and mechanical loads. It is well known that the 2-D EM solution for a solid armature railgun grossly compromises the calculation as compared to the 3-D formulation for isolated regions in the armature and conducting boundary. However, despite this drawback, some success has been obtained in comparing experimental results to the 2-D computations with velocity skin effect, as well as favorable comparisons between 2-D and static 3-D computations. At the present time, there is no code available that accurately captures the entire launch process and physics leading up to and including transition of the armature contacts. It is anticipated that with development of design rules and methodology, the electromagnetic field solution can be extended to 3-D as well as automated to the point that very little computer time and user intervention are required.