Simulation and instrumentation of electromagnetic compression of steel tubes

The near-axisymmetric compression of high strength steel tubes by electromagnetic forming is studied both experimentally and analytically. Tubes with a nominal tensile strength of 440 MPa, outer diameters of 75 mm and wall thicknesses up to 2.3 mm were compressed using a 9 turn helical actuator and discharge energies up to 24 kJ. This can produce reduction in diameters beyond 15%. Experiments were instrumented for measurement of velocity, as well as primary and induced current during the experiments. These records were compared to those of a simple numerical model and found to be in close agreement both in final tube diameter as well as temporal behavior of current and velocity. The model is also exercised to consider system design outside the space examined experimentally. The present experiments also clearly demonstrated that by reducing the system capacitance, the rise time of the pressure pulse can be decreased and this reduces the tendency for Euler bucking in the tubes. This results in rounder tubes, which may be more useful as a manufactured product.