Abstract
In order to study the effect of the loading wedge length on the propagation behavior of stress pulse in a Hopkinson bar loaded fracture test, non-uniform loading bars with different wedge lengths of 0, 3, 15.5 and 40 mm have been machined from a certain rod. The Hopkinson bar loading experiment is performed on one-bar/three-point bend fracture loading system without the bending specimen to avoid the effect of specimen configuration on the reflected pulse. The results indicate that the high frequency oscillations of the reflected pulse are enhanced and the rise time of the reflected pulse increased with increasing wedge length, i.e. the dispersion effect becomes seriously with increasing wedge length. As a consequence, the oscillations in the load-time curves determined using the incident and reflected pulses are more severe for the wedge with larger length. The loading-point displacements calculated are identical when the wedge lengths are 0 and 3 mm. Therefore, in order to decrease the effect of wedge length on stress pulse propagation and to make the loading interface linear contact with specimen, the wedge length should be designed as small as possible.

Key words
Hopkinson pressure bar, wedge-shaped, non-uniform, stress pulse

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