The use of the Hopkinson bar to validate constitutive relations at high rates of strain

Attempts to -validate constitutive relations at high rates of strain have o ften used finite element codes, incorporating the proposed constitutive rel ation, to predict the deformed shape of a given component, e.g. an explosiv ely formed projectile or a Taylor impact test specimen, resulting from the high-rate loading. A more sensitive check, however, of the validity of the given constitutive relation, is its ability to predict the loads required t o produce this deformed shape. Use of the Hopkinson-bar test, where the loa d at which the specimen deforms may be measured, allows such a check to be made. In the present paper tensile Hopkinson-bar tests are performed on Remco iro n specimens and high-speed photography is used to monitor the changing spec imen geometry, allowing a further check of the validity of the proposed con stitutive relation to be made in terms of its ability to predict the observ ed reduction in diameter at the neck. In addition a thermal imaging camera monitors the specimen surface temperature following the high-speed deformat ion and allows a comparison to be made between the temperature profile meas ured experimentally and that predicted in the numerical analysis using two forms of constitutive relation. Crown copyright (C) 1999 Published by Elsev ier Science Ltd. All rights reserved.