SHPB圧縮実験法標準化案の提示とその問題点

Abstract

The standardization of the split Hopkinson pressure bar compression test is attempted to determine stress-strain curves at high constant strain rates, say 1000 s-1, for four types of sheet metal specimen under conditions of uniaxial stress using an extrapolation method. The extrapolation method which is a variant of the well-known Cook and Larke extrapolation method has been established for determining curves of dynamic resistance to homogeneous deformation, i.e., intrinsic stress-strain curves. We use laminated circular plate specimens with four initial ratios of constant diameter to height that is equal to the thickness multiplied by the number of the plate laminated. It is also shown that one of eight striker bars with different kinds of tapered cylindrical shapes enables constant strain rate testing throughout the deformation of specimens. The analysis of the experimental results is conducted as follows: First, the mean stress containing friction effects are graphed against strain. Secondly, curves are cross-plotted with the mean stress as the ordinate and current diameter/height (d/h) ratio as the abscissa for various strains. The extrapolation of a curve back to zero d/h in the figure is expected to be the intrinsic flow stress free of the effect of friction.