In order to provide detailed response data for validation of three dimensional numerical simulations of heterogeneous materials subjected to impact loading, an optically recording velocity interferometer system (ORVIS) has been adapted to a lime-imaging instrument capable of generating precise mesoscopic scale measurements of spatially resolved velocity variations during dynamic deformation. While the use of this diagnostic has been demonstrated on several different classes of heterogeneous materials, studies have focused on pressed granular sugar as a simulant material for the widely used explosive HMX. Tests on this material address mesoscopic scale thermomechanical effects in the absence of complications due to rapid reactions. For low-density (65 percent theoretical maximum density) pressings of sugar, material response has been investigated as a fimction of both impact velocity and changes in particle size distribution. The amplitude and Iiequency of observed transverse and longitudinal wave structures are generally consistent with the highly structured mesoscopic response seen in the 3-D simulations. In parallel with instrumental developments, several approaches for detailed analysis of the spatially resolved velocity-time data are being evaluated. The utility of Fast Fourier Transform (ITT) filtering for reduction of certain types of ORVIS image data has been demonstrated.

In order to provide real-time data for validation of three dimensional numerical simulations of heterogeneous materials subjected to impact loading, an optically recording velocity interferometer system (ORVIS) has been adapted to a line-imaging instrument capable of generating precise mesoscopic scale measurements of spatially resolved velocity variations during dynamic deformation. Combining independently variable target magnification and interferometer fringe spacing, this instrument can probe a velocity field along line segments up to 15 mm in length. In high magnification operation, spatial resolution better than 10 µm can be achieved. For events appropriate to short recording times, streak camera recording can provide temporal resolution better than 0.2 ns. A robust method for extracting spatially resolved velocity-time profiles from streak camera image data has been developed and incorporated into a computer program that utilizes a standard VISAR analysis platform. The use of line-imaging ORVIS to obtain measurements of the mesoscopic scale dynamic response of shocked samples has been demonstrated on several different classes of heterogeneous materials. Studies have focused on pressed, granular sugar as a simulant material for the widely used explosive HMX. For low-density (65 percent theoretical maximum density) pressings of sugar, material response has been investigated as a function of both impact velocity and changes in particle size distribution. The experimental results provide a consistent picture of the dispersive nature of the wave transmitted through these samples and reveal both transverse and longitudinal wave structures on mesoscopic scales. This observed behavior is consistent with the highly structured mesoscopic response predicted by 3-D simulations. Preliminary line-imaging ORVIS measurements on HMX as well as other heterogeneous materials such as foam and glassreinforced polyester are also discussed.4