Incipient spall studies in tantalum - Microstructural effects

Gas gun experiments combined with line-imaging ORVIS velocity interferometric techniques have been used to determine the loading and spall behavior of tantalum at incipient-spall and totally-spalled conditions. An impact velocity of ∼ 0.26 km/s is necessary to induce the incipient spall conditions in tantalum, while it appears that at impact velocities of 0.36 km/s, spallation is almost complete. A 2-mm-long ORVIS line segment is used, so that microstructural effects of spallation at a spatial resolution of less than 50 microns could be determined. Results of these experiments demonstrate a unique feature of this novel test methodology at a microstructural level. The line ORVIS images over this 2-mm segment indicate significant differences in particle-velocity variations in the spall pull-back signal. The observed fluctuations in particle velocity measurements reveal the nucleation and growth of voids and defects in real time at a microstructural level