Standardization of Split Hopkinson Pressure Bar Compression System without Frictional Effects for Metal Plate Specimens

概要

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The effects of variables, such as the dimensions of a test specimen and the friction between the plate specimen and the tools, on the average stress measured in the usual split Hopkinson-Davies pressure bar (SHPB) compression test are estimated, and a method, which is a variant of the well-known Cook and Larke extrapolation method, is established for a constant-strain-rate test using some tapered striker bars to determine the curves of dynamic resistance to homogeneous deformation, i.e., the intrinsic stress-strain curves, by trial and error. The research involves the SHPB compression tests on metal specimens with four or five initial ratios of diameter to height and an analysis of the resulting curves. It is shown that the friction coefficient for various conditions is somewhat complicated and hence it is difficult to estimate the friction coefficient by the SHPB compression test. Then we formulate an extrapolation method to reduce friction to a minimum for the SHPB compression test at a constant strain rate: approximately 1000 [1/s] for metal plate specimens. We conclude that this kind of SHPB system with a constant-strain-rate test followed by the extrapolation procedure is a standard SHPB compression system for metal plate specimens.