Conductivity measurements of MFCG armature material under shock and high strain rates utilizing a split-Hopkinson pressure bar apparatus

Summary form only given, as follows. Modeling and characterization of a Magnetic Flux Compression Generator (MFCG) requires detailed knowledge of the changes in conductivity of the MFCG materials during the shock-loading phase. A split-Hopkinson pressure bar apparatus (SHPB) and current source/differential amplifier setup was used to study shock-loading under controlled conditions while monitoring changes in resistivity in armature material samples. The SHPB apparatus was capable of producing strain rates up to the fracture limit of the samples tested. Actual fracturing of samples would not have allowed detailed analysis of thermal and mechanical effects in sample resistivity changes. Sample strain rate levels of up to 1/spl times/10/sup 4/ strain sec/sup -1/ were achieved with the apparatus on OFHC copper and aluminum samples. This may be comparable to switching contacts under similar shock-loading and is an order of magnitude less than the expected strain rates in the MFCG. Sample resistivity showed an initial and abrupt decrease followed by a rapid increase during loading to levels twice that of virgin samples. Short and long time based resistivity monitoring and high speed framing photography allowed differentiation between changes in resistivity due to bulk material deformation, and changes due to thermal effects.