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Profs. Daehn, Niezgoda, and others receive NSF MRI award

The field of “dynamic behavior of materials” has often stood somewhat separate from the more mainstream fields of “physical metallurgy” and “materials science.” This is partly because dynamic studies require large and dedicated facilities such as gas guns, Hopkinson-Kolsky bars and even explosives.  The MSE team will build the first-of-its-kind equipment that may formalize and standardize new techniques that can make dynamic studies far more accessible. 

Recently, Vivek, Daehn, and co-workers have developed a far more robust and efficient approach that is based on the “exploding conductor” phenomenon that takes place when passing a large current through a thin metal foil or wire. The current adaptation, which consists of the thin conductor with a thick steel anvil on one side and a metallic workpiece on the other, is referred to as the Vaporizing Foil Actuator (VFA) method. The joule heating produces a nearly- instantaneous state change from solid to gas/plasma that can generate several gigapascals of pressure, which can accelerate sheet metal to over 1 km/s in distances of just a few millimeters. The process and equipment are quite robust; excepting the vaporized foil, all of the other components of the system are completely reusable. This develops at least a five-fold improvement in pressures and speeds available in electromagnetic forming with a very reusable system. These pressures and impacts have been shown useful for a number of operations including: impact welding, embossing, precision shape calibration, powder consolidation, adiabatic assisted shearing and the measurement of high strain rate constitutive behavior. In addition, there are basic scientific studies enabled by this equipment. They include both studies of material behavior in rapid, intense loading and studies of the nearly instant solid gas transformation. This new instrument will dramatically improve the experimental throughput, provide much richer data sets and allow studies of equipment robustness, dramatically accelerating progress in the nascent field of Impulse Processing. 

Classes of experiments enabled by the new instrument, from left to right: a) Dynamic Materials Testing, unpublished example of bulk metallic glass fragmentation from collaboration with Prof. K. Flores of Washington, U., b) Impact welding, c) Dynamic Processing exemplified by precision shape calibration and d) VFA Physics, exemplified by laser shadowgram of vaporizing wire 1μs after voltage maximum, anode on the right