Symmetric split Hopkinson compression and tension tests using synchronized electromagnetic stress pulse generators

This work presents an original impact testing arrangement and its applications using two identical synchronized stress pulses to load symmetrically the specimen sandwiched between the two identical Hopkinson pressure bars. In order to obtain two synchronized stress pulses, two identical electromagnetic stress pulse generators connected to the same LC discharge circuit are used. This symmetric impact loading configuration might be easily interchanged into a compressive as well as a tensile version because of the versatility of the electromagnetic stress pulse generators. In order to validate this apparatus, two materials (copper alloy and aluminum alloy) are tested in compression and in tension using this new experimental setup. The measured forces and velocities at the pressure bar/specimen interfaces are indeed identical and simultaneous. The derived material properties of tested materials are compared with those of the traditional split Hopkinson bars and a good agreement is found. A new symmetric Double Cantilever Beam (DCB) test using this experimental device is also presented. It allows overcoming the difficulties of only one moving side in previous work, which avoids an induced mode II component in a DCB test supposed to be a pure mode I testing.