Experimental and numerical study on unreliability of young's modulus measurement by conventional split Hopkinson bar

The split Hopkinson bar (SHB) technique has been widely used to determine dynamic plastic/damage properties of materials at high strain rates. But presently, a number of researchers used it to measure the so-called dynamic Young's moduli. This paper aims at the feasibility to determine Young's moduli by conventional SHB. The strain-stress curves of two kinds of metals, 45# steel and LY-12 aluminum, were measured by a conventional SHB facility. The corresponding numerical experiments were performed by ABAQUS/Explicit. The curves obtained by the both procedures agree well in elastic stage (strain range 0-0.5% assumed). But the slopes of the linearly fitted curves, i.e. the so-called dynamic Young's moduli, are much different from the corresponding real values. The significant errors come from the non-uniformity of stress in specimen during the beginning stage of loading process. The results clarify that it is unfeasible to measure Young's moduli by conventional SHB.