Abstract
A fairly simple modification of the split Hopkinson bar (SHB) method is presented that extends significantly the scope of the Kolsky method in studying the effects of strain rate and strain-rate history on the physical and mechanical properties. The developed modification of the SHB method makes it possible to conduct incremental tests with alternating dynamic loading. Examples illustrating the possibilities of the modifications described are included. In the recent three decades the SHB method, originally proposed by H. Kolsky, has been successfully used all over the world to study strain-rate dependence of the mechanical properties of structural materials. Presently, this method is used to determine the mechanical properties of materials loaded in tension, compression, torsion and 3 — 1 shear CI] for the strain rates of 10 s . In some works this method was used to study the effects of strain-rate history on the mechanical properties of materials [2-63. Most results of this kind have been obtained in the experiments where a dynamic load was superposed on a previously applied static one. There is a number of works where dynamic shifts from one strain rate to another were accomplished during high-rate loading of the specimen C5-63. A Kolsky method modification that allowed to alternate the specimen loading and, thus, to study the dynamic Bauschinger effect was originally developed by Ogawa 171. Some simple modifications of the SHB method have been worked out by the present authors to extend its scope. To create complex strain-rate histories in specimens it is proposed to generate cyclic loads by loading the SHB system using projectiles made up of lengths of two or more bars of materials with different acoustic impedances pC, where p is material density and C is sound velocity in it. The bars the projectile is made up of may follow one another with no gaps between them C8.93 (glued together) or with some gaps CIO].
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