Experimental investigations of visco-plastic properties of the aluminium and tungsten alloys used in KE projectiles

The main aim of studies on dynamic behaviour of construction materials at high strain rates is to determine the variation of mechanical properties (strength, plasticity) in function of the strain rate and temperature. On the basis of results of dynamic tests on the properties of constructional materials the constitutive models are formulated to create numerical codes applied to solve constructional problems with computer simulation methods. In the case of military applications connected with the phenomena of gunshot and terminal ballistics it's particularly important to develop a model of strength and armour penetration with KE projectile founded on reliable results of dynamic experiments and constituting the base for further analyses and optimization of projectile designs in order to achieve required penetration depth. Static and dynamic results of strength investigations of the EN AW-7012 aluminium alloy (sabot) and tungsten alloy (penetrator) are discussed in this paper. Static testing was carried out with the INSTRON testing machine. Dynamic tests have been conducted using the split Hopkinson pressure bars technique at strain rates up to 1,2 · 10 4 s −1 (for aluminium alloy) and 6 · 10 3 s −1 (for tungsten alloy). with the range and the strain rate caused by dynamic loads in the wide range of temperatures allows to create the computer code reflecting in computer simulations the real dynamic processes of material deformation for high strain rates. The measurements of mechanical properties of constructional materials are taken during tensile, compres- sion or torsion tests of material specimens. During tests conducted on standard testing machines the mechanical parameters of material are determined at average strain rate of 5 s −1 . By using testing machines of special design it is possible to determine the mechanical parameters of mate-

[1]  U. S. Lindholm.  Some experiments with the split hopkinson pressure bar , 1964 .

[2]  H. Kolsky.  An Investigation of the Mechanical Properties of Materials at very High Rates of Loading , 1949 .

[3]  R. Davies.  A critical study of the Hopkinson pressure bar , 1948, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[4]  Sia Nemat-Nasser,et al.  Hopkinson techniques for dynamic recovery experiments , 1991, Proceedings of the Royal Society of London. Series A: Mathematical and Physical Sciences.

[5]  I. Daniel.  Experimentation and modeling of composite materials , 1999 .

[6]  Pierre Collet,et al.  An optimisation method for separating and rebuilding one-dimensional dispersive waves from multi-point measurements. Application to elastic or viscoelastic bars , 2002 .

[7]  J. M. Lifshitz,et al.  Data processing in the split Hopkinson pressure bar tests , 1994 .

[8]  B. Hopkinson.  A method of measuring the pressure produced in the detonation of high explosives or by the impact of bullets , 2022 .

[9]  L. Kruszka,et al.  New applications of the Hopkinson pressure bar technique to determining dynamic bahaviour of materials , 1996 .

[10]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

[11]  I. Daniel,et al.  New method for testing composites at very high strain rates , 1981 .

[12]  M. J. Forrestal,et al.  A split Hopkinson bar technique for low-impedance materials , 1999 .

[13]  Geoffrey Ingram Taylor,et al.  The use of flat-ended projectiles for determining dynamic yield stress I. Theoretical considerations , 1948, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.