A rigorous assessment of the benefits of miniaturization in the Kolsky bar system

A rigorous experimental and numerical assessment is made of the benefits and limits of miniaturization in the Kolsky bar system. The primary issues that arise in very high strain rate testing (stress equilibration, inertial effects, wave dispersion, friction, and controllability of deformations) are addressed through experiments coupled with explicit finite element analyses. A miniaturized Kolsky bar system that includes the input bar is developed, together with the use of the laser occlusive radius detector to obtain local measurements of specimen strain during the very high rate deformations. It is demonstrated that this miniaturized Kolsky bar system can be used to provide fully validated results, including the explicit determination of equilibration, over a very wide range of strain rates (1×103 to 5×104 s−1). The desired high strain rate can be achieved even at low accumulated strains, and the total strain developed can be controlled very effectively. Specific conditions are developed for determining the range of utility of the technique for a given material. The technique is applied to the characterization of 6061-T651 aluminum, and the results are compared with the results obtained using a conventional Kolsky bar.

[1]  J. R. Klepaczko,et al.  A unified analytic and numerical approach to specimen behaviour in the Split-Hopkinson pressure bar , 1986 .

[2]  Guruswami Ravichandran,et al.  A micromechanical model for high strain rate behavior of ceramics , 1995 .

[3]  K. T. Ramesh,et al.  Finite deformations and the dynamic measurement of radial strains in compression Kolsky bar experiments , 1996 .

[4]  J. G. Lenard,et al.  An Experimental Study of Interfacial Friction-Hot Ring Compression , 1992 .

[5]  J. Shioiri,et al.  Strain Rate Sensitivity of Flow Stress at Very High Rates of Strain , 1996 .

[6]  Gray,et al.  Classic Split-Hopkinson Pressure Bar Testing , 2000 .

[7]  U. S. Lindholm.  Deformation Maps in the Region of High Dislocation Velocity , 1979 .

[8]  Y. Li,et al.  The compressive viscoplastic response of an A359/SiCp metal-matrix composite and of the A359 aluminum alloy matrix , 2000 .

[9]  D. A. Gorham,et al.  An improved method for compressive stress-strain measurements at very high strain rates , 1992, Proceedings of the Royal Society of London. Series A: Mathematical and Physical Sciences.

[10]  J. Bell,et al.  An experimental diffraction grating study of the quasi-static hypothesis of the split hopkinson bar experiment , 1966 .

[11]  L. Pochhammer,et al.  Ueber die Fortpflanzungsgeschwindigkeiten kleiner Schwingungen in einem unbegrenzten isotropen Kreiscylinder. , 1876 .

[12]  D. A. Gorham,et al.  The effect of specimen dimensions on high strain rate compression measurements of copper , 1991 .

[13]  C. K. H. Dharan,et al.  Determination of stress-strain characteristics at very high strain rates , 1970 .

[14]  K. T. Ramesh,et al.  Effects of nanocrystalline and ultrafine grain sizes on constitutive behavior and shear bands in iron , 2003 .

[15]  J. W. Edington.  The influence of strain rate on the mechanical properties and dislocation substructure in deformed copper single crystals , 1969 .

[16]  C. Chree.  The Equations of an Isotropic Elastic Solid in Polar and Cylindrical Co-ordinates their Solution and Application , 1889 .

[17]  D. A. Gorham,et al.  A numerical method for the correction of dispersion in pressure bar signals , 1983 .

[18]  R. Pick,et al.  MEASUREMENT OF THE BEHAVIOUR OF HIGH-PURITY COPPER AT VERY HIGH RATES OF STRAIN , 1995 .

[19]  D. Bancroft.  The Velocity of Longitudinal Waves in Cylindrical Bars , 1941 .

[20]  G. Wulf.  The high strain rate compression of 7039 aluminium , 1978 .

[21]  D. A. Gorham,et al.  Specimen inertia in high strain-rate compression , 1989 .

[22]  L. D. Bertholf,et al.  Two-dimensional analysis of the split hopkinson pressure bar system☆ , 1975 .

[23]  S. C. Hunter,et al.  The Dynamic Compression Testing of Solids by the Method of the Split Hopkinson Pressure Bar , 1963 .

[24]  L. E. Malvern,et al.  Dispersion Investigation in the Split Hopkinson Pressure Bar , 1990 .