Improvement and application of miniature Hopkinson bar device based on series-parallel coil array electromagnetic launch

To eliminate the electromagnetic deceleration force, remove the limitations of striker bar's length and improve the efficiency for the miniature split Hopkinson pressure bar (mini-SHPB) device, the electromagnetic launch system and energy supply system are improved. The series-parallel coil array launch structure is proposed. The multi-winding parallel coils discharge rapidly to eliminate electromagnetic deceleration force without complex control system or detecting the position of the striker bar in the electromagnetic coils, which can remove the length limitation of striker bar, adjust the stress wave width easily, simplify the multistage launch sensor component structure, and improve the launch velocity greatly without changing the coil geometry parameters. The integrative energy storage structure comprised of “lithium battery + booster module + capacitor group” is proposed. Through the booster module, the capacitor can be charged controllably and the structure can quickly complete many times tests in a single charge, which is secure, reusable and accurate. By using the improved device, the dynamic mechanical properties of Inconel 625 based on laser engineered net shaping (LENS) process are tested in two different build directions under different high strain rates. The tests show that the properties are affected by build direction because of the material anisotropy.