Advertisement

Experimental Mechanics

, 47:659 | Cite as

Radial Inertia Effects in Kolsky Bar Testing of Extra-soft Specimens

  • B. Song
  • Y. Ge
  • W. W. Chen
  • T. Weerasooriya
Article

Abstract

Impact responses of extra-soft materials, such as ballistic gelatins and biological tissues, are increasingly in demand. The Kolsky bar is a widely used device to characterize high-rate behavior of materials. When a Kolsky bar is used to determine the dynamic compressive response of an extra-soft specimen, a spike-like feature often appears in the initial portion of the measured stress history. It is important to distinguish whether this spike is an experimental artifact or an intrinsic material response. In this research, we examined this phenomenon using experimental, numerical and analytical methods. The results indicate that the spike is the extra stress from specimen radial inertia during the acceleration stage of the axial deformation. Based on this understanding, remedies in both specimen geometry and loading pulse to minimize the artifact are proposed and verified, and thus capture the intrinsic dynamic behavior of the specimen material.

Keywords

Kolsky bar Impact testing Radial inertia effect Extra-soft material 

Notes

Acknowledgements

This research was supported by US Army Research Laboratory (ARL) through a collaborative research agreement with Purdue University. The authors wish to thank Dr. Michael Scheidler of ARL for his efforts in the proofreading of the analytical modeling work.

References

  1. 1.
    Kolsky H (1949) An investigation of the mechanical properties of meterials at very high rates of loading. Proc R Soc London, B 62:679–700.Google Scholar
  2. 2.
    Gray GT (2000) Classic split-Hopkinson pressure bar testing. In: ASM Handbook, Mechanical testing and evaluation vol 8, Materials Park, OH, pp 462–476.Google Scholar
  3. 3.
    Song B, Chen W (2004) Dynamic stress equilibration in split Hopkinson pressure tests on soft materials. Exp Mech 44:300–312.CrossRefGoogle Scholar
  4. 4.
    Gray GT, Blumenthal WR (2000) Split-Hopkinson pressure bar testing of soft materials. In: ASM Handbook, Mechanical testing and evaluation vol 8, Materials Park, OH, pp 488–496.Google Scholar
  5. 5.
    Dioh NN, Ivankovic A, Leevers PS, Williams JG (1995) Stress wave propagation effects in split Hopkionson pressure bar tests. Proc R Soc London, A 499:187–204.Google Scholar
  6. 6.
    Gray GT, Blumenthal WR, Trujillo CP, Carpenter RW (1997) Influence of temperature and strain rate on the mechanical behavior of adiprene L-100. J Phys IV France Colloque C3 (DYMAT 97) 7:523–528.Google Scholar
  7. 7.
    Chen W, Lu F, Frew DJ, Forrestal MJ (2002) Dynamic compression testing of soft materials. J Appl Mech 69:214–223.zbMATHCrossRefGoogle Scholar
  8. 8.
    Wu XJ, Gorham DA (1997) Stress equilibrium in the split Hopkinson pressure bar test. J Phys IV France C3:91–96.Google Scholar
  9. 9.
    Chen W, Zhang B, Forrestal MJ (1999) A split Hopkinson bar technique for low-impedance materials. Exp Mech 39:81–85.CrossRefGoogle Scholar
  10. 10.
    Chen W, Lu F, Zhou B (2000) A quartz-crystal-embedded split Hopkinson pressure bar for soft materials. Exp Mech 40:1–6.zbMATHCrossRefGoogle Scholar
  11. 11.
    Song B, Chen W (2003) One-dimensional dynamic compressive behavior of EPDM rubber. J Eng Mater Technol 125:301–394.CrossRefMathSciNetGoogle Scholar
  12. 12.
    Song B, Chen W (2004) Dynamic compressive behavior of EPDM rubber under nearly uniaxial strain conditions. J Eng Mater Technol 126:213–217.CrossRefGoogle Scholar
  13. 13.
    Song B, Chen W, Jiang X (2005a) Split Hopkinson pressure experiments on polymeric foams. Int J Veh Des 37:185–198.CrossRefGoogle Scholar
  14. 14.
    Shergold OA, Fleck NA, Radford D (2006) The uniaxial stress versus strain response of pig skin and silicone rubber at low and high strain rates. Int J Impact Eng 32:1384–1402.CrossRefGoogle Scholar
  15. 15.
    Song B, Chen W (2005) Split Hopkinson pressure bar techniques for characterizing soft materials. Lat Am J Solids Struct 2:113–152.Google Scholar
  16. 16.
    Fung YC (1993) Biomechanics: mechanical properties of living tissues, 2nd edn. Springer, Berlin Heidelberg New York.Google Scholar
  17. 17.
    Product description of rubber and foam: ultra-elastic clear gel rubber, http://www.mcmaster.com.
  18. 18.
    Lindholm US (1964) Some experiments with split Hopkinson pressure bar. J Mech Phys Solids 12:317–335.CrossRefGoogle Scholar
  19. 19.
    Follansbee PS, Frantz C (1983) Wave propagation in the split Hopkinson pressure bar. J Eng Mater Technol 105:61–66.CrossRefGoogle Scholar
  20. 20.
    Davies E, Hunter SC (1963) The dynamic compression testing of solids by the method of the split Hopkinson pressure bar. J Mech Phys Solids 11:155–179.CrossRefGoogle Scholar
  21. 21.
    Gorham DA, Pope PH, Cox O (1984) Sources of error in very high strain rate compression tests. Inst Phys Conf Ser 70:151–158.Google Scholar
  22. 22.
    Malinowski JZ, Klepaczko JR (1986) A unified analytic and numerical approach to specimen behaviour in the split-Hopkinson pressure bar. Int J Mech 28:381–391.CrossRefGoogle Scholar
  23. 23.
    Gorham DA (1989) Specimen inertia in high strain-rate compression. J Phys, D, Appl Phys 22:1888–1893.CrossRefGoogle Scholar
  24. 24.
    Gorham DA (1991) The effect of specimen dimensions on high strain rate compression measurements of copper. J Phys, D, Appl Phys 24:1489–1492.CrossRefGoogle Scholar
  25. 25.
    Forrestal MJ, Wright TW, Chen W (2006) The effect of radial inertia on brittle samples during the split Hopkinson pressure bar test. Int J Impact Eng 34:405–411.CrossRefGoogle Scholar
  26. 26.
    Syn CJ (2004) Radial inertia effects through sample geometry change. M.S. thesis, University of Arizona.Google Scholar
  27. 27.
    Avitzur B (1968) Metal forming: processes and analysis. McGraw-Hill, New York.Google Scholar
  28. 28.
    Johnson AR, Quigley CJ, Freese CE (1995) A viscohyperelastic finite-element model for rubber. Comput Methods Appl Mech Eng 127:163–180.zbMATHCrossRefGoogle Scholar
  29. 29.
    Chung DT (1996) The effect of specimen shape on dynamic flow stress. In: Schmidt SC, Tao WC (eds) Shock compression of condensed matter 1995, vol 370. American Institute of Physics, Woodbury, New York, pp 483–486.Google Scholar
  30. 30.
    Duffy J, Campbell JD, Hawley RH (1971) On the use of a torsional split Hopkinson bar to study rate effects in 1100-0 aluminum. J Appl Mech 37:83–91.Google Scholar
  31. 31.
    Christensen RJ, Swanson SR, Brown WS (1972) Split-Hopkinson-bar tests on rocks under confining pressure. Exp Mech 11:508–513 (November).CrossRefGoogle Scholar
  32. 32.
    Parry DJ, Walker AG, Dixon PR (1995) Hopkinson bar pulse smoothing. Meas Sci Technol 6:443–446.CrossRefGoogle Scholar
  33. 33.
    Follansbee PS (1985) The Hopkinson bar. In: ASM Handbook, Mechanical testing and evaluation, vol 8. Materials Park, OH, pp 198–203.Google Scholar
  34. 34.
    Song B, Chen W (2005) Split Hopkinson pressure bar technique for characterizing soft materials. Lat Am J Solids Struct 2:113–152.Google Scholar

Copyright information

© Society for Experimental Mechanics 2007

Authors and Affiliations

  1. 1.School of Aeronautics and Astronautics and School of Materials EngineeringPurdue UniversityWest LafayetteUSA
  2. 2.School of Aeronautics and AstronauticsPurdue UniversityWest LafayetteUSA
  3. 3.Impact Physics BranchUS Army Research LaboratoryAberdeen Proving GroundUSA

Personalised recommendations