Conference Proceedings of the Society for Experimental Mechanics Series
Olles, Joseph D.; Hudspeth, Matthew; Tilger, Christopher F.; Garasi, Christopher; Sanchez, Nathaniel; Jensen, Brian
Material strength properties for metals under shock loading conditions were investigated using high-fidelity, ultra-high-speed X-ray diagnostics. High-strain rate Richtmyer-Meshkov instability (RMI) experiments were performed with an explosive powder driven gas gun at the Advanced Photon Source (APS) located at Argonne National Laboratory. Metal targets (copper and aluminum) with a prescribed sinusoidal interface, were studied using photonic Doppler velocimetry (PDV) and X-ray phase contrast imaging (PCI). The metal targets were impacted at velocities up to ~2.25 mm/μs with subsequent maximum strain rates ranging between 107–108 s−1. The instability was recorded using X-ray PCI having a spatial resolution of 2–3 microns with sub-nanosecond exposures. Due to the constructive/destructive interference of X-rays and other challenges with artifacts associated with PCI, edge extraction must be robust against deviations in brightness, contrast, and noise. For the experimental images, a phase congruency feature detection algorithm outputs quantitative descriptors of edges for the metal jet size and shape. Computational hydrocode simulations were used to fit parameters for various strength models, with good agreement. The spatial and temporal resolution of our measurements allow validation and expansion of previously documented literature on these materials.
The breakup of liquids due to aerodynamic forces has been widely studied. However, the literature contains limited quantified data on secondary droplet sizes, particularly as a function of time. Here, a column of liquid water is subjected to a step change in relative gas velocity using a shock tube. A unique digital in-line holography (DIH) configuration is proposed which quantifies the secondary droplets sizes, three-dimensional position, and three-component velocities at 100 kHz. Results quantify the detailed evolution of the characteristic mean diameters and droplet size-velocity correlations as a function of distance downstream from the initial location of the water column. Accuracy of the measurements is confirmed through mass balance. These data give unprecedented detail on the breakup process which will be useful for improved model development and validation.