Modeling Assumptions for Railguns

Insights from recovered armatures suggest re-examining historical modeling assumptions for railguns. The finite-element codes EMAP3D and DYNA3D were linked to explore the effects of temperature-dependent material properties, thermal diffusion, armature wear, inertial loading, thermal stresses, and 2-D model approximations. Temperatures and principal stresses for each of these cases were compared. Thermal diffusion and thermal stresses in armatures cannot be ignored past the first millisecond of launch; material properties under pulsed heating can significantly differ from equilibrium and room-temperature values. Armature wear and inertial loading can be ignored at low speeds, but not at high speeds (>1 km/s). Models in 2-D can approximate 3-D models with appropriate boundary conditions, but only for the first few milliseconds of launch. With a detailed EMAP3D model and minimal assumptions, simulations that agree within a few percentage points of microstructural measurements from recovered armatures are possible