Specimen Size Effects on the Compressive Stress-Strain Response of Equal Channel Angular Extrusion (ECAE) Tantalum
[Technical Report, Technical Report]
CCDC Army Research Laboratory
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Compression tests were performed on tantalum over a range of strain rates using conventional servo-hydraulic load frames and the Kolsky split-Hopkinson pressure bar. To obtain a large range of strain rates 0.001s to 500ks, different diameter Kolsky bars were required 3.18 mm, 1.59 mm, 794 um, and 305 um. These different bars were used to test different sample geometries nominally 1.6-, 0.8-, and 0.4-mm cubes, and small cylinders with 60-um diameter and 30-um height. It was found that the four different sample sizes led to drastically different measured strengths, even for samples tested at the same strain rates. The tantalum studied has a fine grain structure 2 um so this is not believed to be due to the grain size. However, the reason for the discrepancy is unknown.
- Metallurgy and Metallography