93
16.5 Conclusion
A novel Tension-Torsion Split Hopkinson Bar apparatus is built to achieve an arbitrary combination of tensile and shear
wave loading. The apparatus is demonstrated via bar-attached tests to generate combined tensile and shear waves with favorably short rise time and smooth wave form. The length of the waves corresponds to the length of the pre-stressed section of
the input bar, and the magnitude is correlated to the amount of the stored tensile or torsional elastic energy. Wave synchronization can be approximately satisfied by a proper selection of the short distance between the clamp and the input bar–output bar interface. The full capacity of TTHB will be further demonstrated by means of experiments on commercially available
pure titanium. A data processing method for the complex stress state will be established and the rate-dependent behavior of
the material subjected to complex stress states will be analyzed and reported. The failure surface of specimens subjected to
a prescribed combination of tension and torsion will be assessed using optical profilometry and scanning electron microscope.
Acknowledgments The research is sponsored by EPSRC and Rolls- Royce plc as part of the Prosperity Partnership (Cornerstone) project. We are
grateful to S. Carter, J. Fullerton, and P. Tantrum for their assistance with the apparatus manufacturing and assembly.
References
1. Gerlach, R., Kettenbeil, C., Petrinic, N.: A new split Hopkinson tensile bar design. Int. J. Impact Eng. 50, 63–67 (2012)
2. Gray III, G.T.: Classic split-Hopkinson pressure bar testing. In: Kuhn, H., Medlin, D. (eds.) ASM Handbook, Mechanical Testing and
Evaluation, vol. 8, pp. 462–476. ASM International, Materials Park, OH (2000)
3. Harding, J., Welsh, L.M.: A tensile testing technique for fibre- reinforced composites at impact rates of strain. J. Mater. Sci. 18(6),
1810–1826 (1983)
4. Staab, G.H., Gilat, A.: A direct-tension split Hopkinson bar for high strain-rate testing. Exp. Mech. 31, 232–235 (1991)
5. Pope, D.P., Vreeland Jr., T., Wood, D.S.: Machine for producing square torsion pulses of micro-second duration. Rev. Sci. Instrum. 35,
1351–1355 (1964)
6. Lewis, J.L., Goldsmith, W.: The dynamic fracture and prefracture response of compact bone by split Hopkinson bar methods. J. Biomech. 8,
27–40 (1975)
7. Hartley, K.A., Duffy, J., Hawley, R.H.: The Torsional Kolsky (Split-Hopkinson) Bar, Mechanical Testing ASM Handbook, vol. 8, pp. 218–228.
ASM International, Materials Park, OH (1985)
8. Gilat, A., Cheng, C.-S.: Torsional split Hopkinson bar tests at strain rates above 104 s
-1
. Exp. Mech. 40(1), 54–59 (2000)
9. Duffy, J., Campbell, J.D., Hawley, R.H.: On the use of a torsional split Hopkinson bar to study rate effects in 1100-O aluminum. J. Appl. Mech.
38, 83–91 (1971)
10. Frantz, R.A., Duffy, J.: The dynamic stress-strain behavior in torsion of 1100-0 aluminum subjected to a sharp increase in strain rate. J. Appl.
Mech. 39, 939–945 (1972)
Fig. 16.3 Bar-attached
validation: combined tensile
and shear waves
16 The Development of Split Hopkinson Tension-Torsion Bar for the Understanding of Complex Stress States at High Rate
16.5 Conclusion
A novel Tension-Torsion Split Hopkinson Bar apparatus is built to achieve an arbitrary combination of tensile and shear
wave loading. The apparatus is demonstrated via bar-attached tests to generate combined tensile and shear waves with favorably short rise time and smooth wave form. The length of the waves corresponds to the length of the pre-stressed section of
the input bar, and the magnitude is correlated to the amount of the stored tensile or torsional elastic energy. Wave synchronization can be approximately satisfied by a proper selection of the short distance between the clamp and the input bar–output bar interface. The full capacity of TTHB will be further demonstrated by means of experiments on commercially available
pure titanium. A data processing method for the complex stress state will be established and the rate-dependent behavior of
the material subjected to complex stress states will be analyzed and reported. The failure surface of specimens subjected to
a prescribed combination of tension and torsion will be assessed using optical profilometry and scanning electron microscope.
Acknowledgments The research is sponsored by EPSRC and Rolls- Royce plc as part of the Prosperity Partnership (Cornerstone) project. We are
grateful to S. Carter, J. Fullerton, and P. Tantrum for their assistance with the apparatus manufacturing and assembly.
References
1. Gerlach, R., Kettenbeil, C., Petrinic, N.: A new split Hopkinson tensile bar design. Int. J. Impact Eng. 50, 63–67 (2012)
2. Gray III, G.T.: Classic split-Hopkinson pressure bar testing. In: Kuhn, H., Medlin, D. (eds.) ASM Handbook, Mechanical Testing and
Evaluation, vol. 8, pp. 462–476. ASM International, Materials Park, OH (2000)
3. Harding, J., Welsh, L.M.: A tensile testing technique for fibre- reinforced composites at impact rates of strain. J. Mater. Sci. 18(6),
1810–1826 (1983)
4. Staab, G.H., Gilat, A.: A direct-tension split Hopkinson bar for high strain-rate testing. Exp. Mech. 31, 232–235 (1991)
5. Pope, D.P., Vreeland Jr., T., Wood, D.S.: Machine for producing square torsion pulses of micro-second duration. Rev. Sci. Instrum. 35,
1351–1355 (1964)
6. Lewis, J.L., Goldsmith, W.: The dynamic fracture and prefracture response of compact bone by split Hopkinson bar methods. J. Biomech. 8,
27–40 (1975)
7. Hartley, K.A., Duffy, J., Hawley, R.H.: The Torsional Kolsky (Split-Hopkinson) Bar, Mechanical Testing ASM Handbook, vol. 8, pp. 218–228.
ASM International, Materials Park, OH (1985)
8. Gilat, A., Cheng, C.-S.: Torsional split Hopkinson bar tests at strain rates above 104 s
-1
. Exp. Mech. 40(1), 54–59 (2000)
9. Duffy, J., Campbell, J.D., Hawley, R.H.: On the use of a torsional split Hopkinson bar to study rate effects in 1100-O aluminum. J. Appl. Mech.
38, 83–91 (1971)
10. Frantz, R.A., Duffy, J.: The dynamic stress-strain behavior in torsion of 1100-0 aluminum subjected to a sharp increase in strain rate. J. Appl.
Mech. 39, 939–945 (1972)
Fig. 16.3 Bar-attached
validation: combined tensile
and shear waves
16 The Development of Split Hopkinson Tension-Torsion Bar for the Understanding of Complex Stress States at High Rate