Mechanical Behavior of Ta at Extreme Strain-Rates
The compressive stress-strain response of a commercially pure (99.98%) Ta was investigated at strain-rates ranging from 0.001/s to 500 k/s. Strain-rates up to 20 k/s were obtained using conventional load frames and Kolsky bar methods. The higher strain-rates were obtained using optically instrumented miniature Kolsky bars. Because these experiments require sample sizes as small as ∼30 um, a fine grain structure was desired. To achieve this, we study a Ta billet that was processed by ECAE to produce an ultrafine grain structure. The billets were subsequently annealed at 1203 K under high vacuum for 2 h to coarsen the grain size to approximately 2 um. The as-worked and annealed microstructures were investigated by electron backscatter diffraction to verify the grain structure. A strong rate dependence is observed over this range of strain-rates, although there is a discrepancy between data at similar strain-rates using different sample sizes. This discrepancy is the subject of on-going investigation.
KeywordsTantalum Split Hopkinson pressure bar Kolsky bar High strain-rate Plasticity
The authors would like to thank Mr. Kevin Taylor for his help conducting the low-rate experiments and for preparing the samples.
- 2.Casem, D.T.: A Small Diameter Kolsky bar for High-rate Compression. Proc. of the 2009 SEM Annual Conference and Exposition on Experimental and Applied Mechanics, Albuquerque, NM, 1–4 June 2009Google Scholar
- 6.Casem, D.T., Huskins, E.L., Ligda, J., Schuster, B.E.: A Kolsky Bar for High-rate Micro-compression – Preliminary Results. In: Proc. 2015 SEM Annual Conference and Exposition, Springer, Costa Mesa, CA (2015)Google Scholar
- 10.Casem, D.T., Ligda, J.P., Schuster, B.E., Mims, S.: High-rate mechanical response of aluminum using miniature Kolsky bar techniques. In: Kimberley, J., Lamberson, L., Mates, S. (eds.) Dynamic Behavior of Materials, Volume 1. Conference Proceedings of the Society for Experimental Mechanics Series. Springer, Cham (2018)Google Scholar