Analysis on the waveform features of the split Hopkinson pressure bar tests of plain concrete specimen

The tendency of the waveform curve can directly reflect the deformation and failure process of specimen in the SHPB (Split Hopkinson Pressure Bar) test of concrete. Different loading rates will result in the different ultimate failure modes, waveform curves and the stress strain curves of the concrete specimens. Furthermore, these differences are obviously characterized by some feature points of waveform or stress strain curves. In the present study, with the pulse shaping technique and high-speed photograph, large dimension (0120 x 100 mm) SHPB tests of concrete specimen have been conducted. The typical features of the waveform curves under different loading rates have been further classified. According to the experimental observation, the double-peak phenomenon of reflection wave in the SHPB tests of concrete-like materials is revealed and interpreted, as well as the compression wave phenomenon occurring in the tail of reflection wave under relatively lower strain rate and the obvious post-peak inward cohcave descending of the transmission wave under high strain rate. What's more, the plastic carrying capacity and the effect of the strain rate are also studied. Some empirical understanding on the correspondence between the waveform features and the ultimate failure status of the concrete specimen under various loading rates are also presented. The above research shows that compression wave phenomenon of the reflection wave and sustainable plastic carrying capacity will vanish with the increasing loading rate. On the contrary, the doubl-peak phenomenon of the reflection wave, which is considered to be the specific property possessed by concrete -like materials, will become more apparent with the increasing loading rate. (C) 2017 Elsevier Ltd. All rights reserved.