71
displacement interferometer (TDI) is used at the midpoint of the input bar to measure the incident and reflected pulses. This
involves the use of a diffraction grating, which if used for the tension bar would require a much longer input bar than planned
here to ensure adequate distance to accelerate the striker. Since long thin bars are difficult to make with sufficient precision
at this size range, the use of an NDI on the input bar has an advantage over one which would require either a TDI or straingage on the input bar.
As a final note, the use of the small bars with optical instrumentation has an additional advantage for this type of mechanical testing. Although we are not especially interested in obtaining high strain rates, we are interested in obtaining as much
information as possible about the failure process. This can occur quite rapidly and requires a method of measuring the force
in the sample with a high temporal resolution. Casem et al. [6] have shown that a steel bar with a 300 μm diameter and interferometer instrumentation can be used to measure frequencies as high as 7 MHz, which hopefully will provide details of the
nature of stress collapse that can inform failure models. We know of no other transducer that can meet this need.
References
1. Chen, W., Song, B.: Split Hopkinson (Kolsky) Bar. Springer (2011).
2. Follansbee, P.S.: The Hopkinson bar. In: Metals Handbook, vol. 8(9), pp. 198–217. American Society for Metals, Metals Park, OH (1985)
3. Jia, D., Ramesh, K.T.: A rigorous assessment of the benefits of miniaturization in the Kolsky Bar system. Exp. Mech. 44, 445–454 (2004)
4. Malinowski, J.Z., Klepaczko, J.R., Kowalewski, Z.L.: Miniaturized compression test at very high strain rates by direct impact. Exp. Mech. 47,
451–463 (2007)
5. Casem, D.T., Grunschel, S.E., Schuster, B.E.: Normal and transverse displacement interferometers applied to small diameter Kolsky bars. Exp.
Mech. 52(2), 173–184 (2012)
6. Casem, D., Ligda, J., Walter, T., Darling, K., Hornbuckle, B.: Strain-rate sensitivity of nanocrystalline Cu–10Ta to 700,000/s. J. Dyn. Behav.
Mater. 6, 1–10 (2019)
7. Nicholas, T., Bless, S.J.: High rate tension testing. In: ASM Metals Handbook, vol. 8, pp. 208–214. American Society for Metals, Metals Park,
OH (1985)
8. Ogawa, K.: Impact-tension compression test by using a split- Hopkinson bar. Exp. Mech. 24, 81–86 (1984)
9. Lindholm, U.S., Yeakley, L.M.: High strain rate testing: tension and compression. Exp. Mech. 8, 1–9 (1968)
10. Staab, G., Gilat, A.: A direct-tension split Hopkinson bar for high strain-rate testing. Exp. Mech. 31(3), 232–235 (1991)
11. Hartley, K., Duffy, J., Hawley, R.: The torsional Kolsky (split- Hopkinson) bar. In: ASM Metals Handbook, vol. 8, pp. 218–228. American
Society for Metals, Metals Park, OH (1985)
12. Guzman, O., Frew, D.J., Chen, W.: A Kolsky tension bar technique using a hollow incident tube. Measur. Sci. Technol. 22(4), 045703 (2011)
13. Gerlach, R., Kettenbeil, C., Petrinic, N.: A new split Hopkinson tensile bar design. Int. J. Impact Eng. 50, 63–67 (2012). https://doi.org/10.1016/j.
ijimpeng.2012.08.004
14. Sanborn, B.M.F., Moy, P., Weerasooriya, T.: Micro-tensile experimental methods to study the dynamic behavior of thin metallic films. In
Proceedings of the society of experimental mechanics annual conference, Lombard, IL (2014).
15. Cheng, M., Chen, W., Weerasooriya, T.: Mechanical properties of Kevlar
® KM2 single fiber. J. Eng. Mater. Technol. 127, 197–203 (2005)
13 Development of a Micro Tensile Kolsky Bar
displacement interferometer (TDI) is used at the midpoint of the input bar to measure the incident and reflected pulses. This
involves the use of a diffraction grating, which if used for the tension bar would require a much longer input bar than planned
here to ensure adequate distance to accelerate the striker. Since long thin bars are difficult to make with sufficient precision
at this size range, the use of an NDI on the input bar has an advantage over one which would require either a TDI or straingage on the input bar.
As a final note, the use of the small bars with optical instrumentation has an additional advantage for this type of mechanical testing. Although we are not especially interested in obtaining high strain rates, we are interested in obtaining as much
information as possible about the failure process. This can occur quite rapidly and requires a method of measuring the force
in the sample with a high temporal resolution. Casem et al. [6] have shown that a steel bar with a 300 μm diameter and interferometer instrumentation can be used to measure frequencies as high as 7 MHz, which hopefully will provide details of the
nature of stress collapse that can inform failure models. We know of no other transducer that can meet this need.
References
1. Chen, W., Song, B.: Split Hopkinson (Kolsky) Bar. Springer (2011).
2. Follansbee, P.S.: The Hopkinson bar. In: Metals Handbook, vol. 8(9), pp. 198–217. American Society for Metals, Metals Park, OH (1985)
3. Jia, D., Ramesh, K.T.: A rigorous assessment of the benefits of miniaturization in the Kolsky Bar system. Exp. Mech. 44, 445–454 (2004)
4. Malinowski, J.Z., Klepaczko, J.R., Kowalewski, Z.L.: Miniaturized compression test at very high strain rates by direct impact. Exp. Mech. 47,
451–463 (2007)
5. Casem, D.T., Grunschel, S.E., Schuster, B.E.: Normal and transverse displacement interferometers applied to small diameter Kolsky bars. Exp.
Mech. 52(2), 173–184 (2012)
6. Casem, D., Ligda, J., Walter, T., Darling, K., Hornbuckle, B.: Strain-rate sensitivity of nanocrystalline Cu–10Ta to 700,000/s. J. Dyn. Behav.
Mater. 6, 1–10 (2019)
7. Nicholas, T., Bless, S.J.: High rate tension testing. In: ASM Metals Handbook, vol. 8, pp. 208–214. American Society for Metals, Metals Park,
OH (1985)
8. Ogawa, K.: Impact-tension compression test by using a split- Hopkinson bar. Exp. Mech. 24, 81–86 (1984)
9. Lindholm, U.S., Yeakley, L.M.: High strain rate testing: tension and compression. Exp. Mech. 8, 1–9 (1968)
10. Staab, G., Gilat, A.: A direct-tension split Hopkinson bar for high strain-rate testing. Exp. Mech. 31(3), 232–235 (1991)
11. Hartley, K., Duffy, J., Hawley, R.: The torsional Kolsky (split- Hopkinson) bar. In: ASM Metals Handbook, vol. 8, pp. 218–228. American
Society for Metals, Metals Park, OH (1985)
12. Guzman, O., Frew, D.J., Chen, W.: A Kolsky tension bar technique using a hollow incident tube. Measur. Sci. Technol. 22(4), 045703 (2011)
13. Gerlach, R., Kettenbeil, C., Petrinic, N.: A new split Hopkinson tensile bar design. Int. J. Impact Eng. 50, 63–67 (2012). https://doi.org/10.1016/j.
ijimpeng.2012.08.004
14. Sanborn, B.M.F., Moy, P., Weerasooriya, T.: Micro-tensile experimental methods to study the dynamic behavior of thin metallic films. In
Proceedings of the society of experimental mechanics annual conference, Lombard, IL (2014).
15. Cheng, M., Chen, W., Weerasooriya, T.: Mechanical properties of Kevlar
® KM2 single fiber. J. Eng. Mater. Technol. 127, 197–203 (2005)
13 Development of a Micro Tensile Kolsky Bar