Measuring strength of materials at very high strain rates using electromagnetically driven expanding cylinders

In this work we developed a new methodology to measure the strength of materials at very high strain rates, using magnetically driven expanding cylinder experiments by the means of a pulse current generator (PCG). The expansion of the specimen is done using a ``pusher'' configuration, enabling one cylinder which carries the magnetic load to push out the external tested material, with negligible effects of the current/magnetic field on it. This allows also to test with this technique any material, regardless its conductivity. We use a hybrid analysis methodology to measure and define the yield stress in the tests, using the combination of experimental and numerical analyses. The analysis is conducted at the \textit{forced} stage of acceleration unlike standard expanding ring/cylinder tests in the literature which use the free ?ight stage for the strength analysis. This allows to take advantage of the high rate regime, dominated by the fast rise-time of the PCG and thus to reach very high strain rates. The technique is demonstrated for OFHC copper up to strain rates of 7.5$\cdot $10$^{\mathrm{4}}$ sec$^{\mathrm{-1}}$ and is compared with other results in the literature for this material.