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The role of friction in high strain-rate events is not well understood despite being an important constitutive relationship in modern modeling and simulation studies of explosive events. There is a lack of experimental data available for the validation ofmodels of dynamic sliding. The Rotating Barrel Gas Gun (RBGG) is a novel, small-scale experimental facility designed to investigate interfacial dynamics at high loads and sliding speeds. The RBGG utilizes a low-pressure gas gun to propel a rotating annular projectile towards an annular target rod. Upon striking the target, the projectile imparts both an axial and a torsional impulse into the target at a timescale relevant to explosively-driven events. Resulting elastic waves are measured using strain gages attached to the target rod. The coefficient of friction is obtained through an analysis of the resulting strain wave data. Initial experiments have been performed using dry copper/copper interfaces. We find that the measured coefficient of friction can evolve significantly over a 30 μs event. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Gated infrared (IR) images have been taken of a series of shocked surface geometries in tin. Metal coupons machined with steps and flats were mounted directly to the high explosive. The explosive was point-initiated and 500-ns to 1-microsecond-wide gated images of the target were taken immediately following shock breakout using a Santa Barbara Focalplane InSb camera (SBF-134). Spatial distributions of surface radiance were extracted from the images of the shocked samples and found to be non-single-valued. Several surfaces were modeled using CTH, a 2- or 3-dimensional Eulerian hydrocode. [ABSTRACT FROM AUTHOR]

The physical interactions at the contact interface between two metals moving relative to one another are not well understood, particularly when the relative velocity between the bodies becomes a significant fraction of the sound speed in either material. Our goal is to characterize the interfacial dynamics occurring between two metal surfaces sliding at high loads (up to 300 kbar) and at high speeds (greater than 100 m/s). We are developing a technique where a high-speed spinning projectile is fired from a rifled gun at a rod instrumented with electrical resistance strain gauges for measuring both longitudinal and torsional strain waves. The observed traces, in conjunction with computer simulations, are used to estimate the normal and tangential force components at the interface to produce an estimate of the coefficient of friction. A preliminary estimate for a copper/steel interface is presented. [ABSTRACT FROM AUTHOR]

Provides a corrected reprint of an article on high-speed impact experiments, published in the 1999 edition of the periodical 'Shock Compression of Condensed Matter.'