High-Strain-Rate Facility
The single-stage gas gun facility is equipped with interferometric, stress-gauge, high-speed digital data acquisition, and ultra-high speed digital photographic instrumentation, permitting material testing at strain rates up to 106 s-1 under a range of multiaxial states of stress through normal and pressure-shear (inclined) plate impact experiments. The gas gun has an 80 mm diameter, 8 m long gun barrel connected to a 28.5 liter gas chamber which is separated via a double (rupture) diaphragm on the breech side and is connected to a large soft-recovery catcher tank on the muzzle side. Impact velocities between 200 to 1200 ms-1 (reproducible within 5%) can be obtained, and are monitored using four sets of arrival-time velocity pins, connected to a Tektronix Model 640 digitizing oscilloscope as well as digital counters (HP Model No. 5313A, 2 channel, 225 MHz). Time-resolved in-situ stress measurements can be performed using piezoelectric PVDF as well as piezoresistive manganin stress gauges. Particle velocity measurements using a state-of-the-art VISAR (Velocity Interferometer System for Any Reflector) interferometry can also be made. This VISAR system is capable of measuring free surface velocities in the range of 30-5000 ms-1 with a sensitivity of (+/-)2 ms-1 and a depth of field of 12 mm. Simultaneous measurements can be performed at any four locations on a plane. Two four-channel Tektronix digital oscilloscopes (Model TDS784A) with a sampling rate of 4 Giga points per second are available for high-speed data acquisition. An IMACON high-speed digital camera (16 frames at 200x106 f/s) is also available for time-resolved diagnostics of impact events.