Photon Doppler velocimetry measurements of the impact velocity during electromagnetic pulse welding of copper-steel tubular joints

Tubular copper to steel joints were manufactured by electromagnetic pulse welding, during which the impact velocity was measured with photon Doppler velocimetry. The reduction in inner diameter and the remaining cross-sectional area of the target tube were determined after welding. Tube-to-tube configurations with an internal support exhibited a larger remaining cross-sectional area, compared to the configuration without internal support. Moreover, for the tube-to-rod configuration, the initial velocity drop immediately after impact dropped down to zero, whereas for the tube-to-tube configurations, a velocity drop to an intermediate level was found. The velocity and acceleration increased with an increase of the discharge energy. The acceleration was positive up to at least 9 μs, with an expected turning point situated between 9 μs and 11 μs. The acceleration was still positive at the moment of impact at a stand off distance of 1.0 mm and 1.5 mm, but was likely negative at 2.0 mm.