Abstract
The propagation characteristics of viscoelastic waves have been investigated with a 6 mm diameter split Hopkinson pressure bar (SHPB) made of polymethyl methacrylate (PMMA). The strain signals in SHPB tests were improved by the pulse shaping technique. Based on the experimentally determined propagation coefficients, the amplitude attenuation and wave dispersion induced by viscoelastic effects at different impact velocities were quantitatively analyzed. The results indicate that the high-frequency harmonics attenuate faster in a higher phase velocity. With an increase in the impact velocity, the amplitude attenuation of the viscoelastic wave changes slightly during propagation, while the waveform dispersion gradually intensifies. A feasible method by waveform prediction was proposed to verify the validity and applicability of the propagation coefficient. The results indicate that the strain obtained from the small diameter viscoelastic SHPB can be effectively modified by utilizing the propagation coefficient. Furthermore, it is preferred to adopt the propagation coefficient obtained at low impact velocity for correction when the impact velocity varies. Moreover, the PMMA-steel bar impact test was performed to further illustrate the accuracy of the propagation coefficient and the effectiveness of the correction method.
Highlights
It is well known that the split Hopkinson pressure bar (SHPB) is a widely utilized technique for exploring the dynamic mechanical behavior of materials [1,2,3]
Attenuation and Dispersion in Wave Propagation. e signals on the incident bar in Figure 4 can be divided into incident waves and reflected waves by the threshold method. en, the propagation coefficients are obtained by equation (6). e attenuation coefficients and phase velocities are obtained by equation (4)
It can be found that when the impact velocity changes within a certain range, the same propagation coefficient can be used for correction
Summary
It is well known that the split Hopkinson pressure bar (SHPB) is a widely utilized technique for exploring the dynamic mechanical behavior of materials [1,2,3]. Numerical simulation provides the possibility to reveal the important micromechanism of wave propagation, specimen failure, and the strain rate effect in the SHPB test. Employing a proper pulse shaper is one of the effective methods to improve the incident waveform, which helps to achieve the dynamic equilibrium state and to meet the condition of constant strain rate in the test specimen [7, 8]. Li et al [11] reported that the strain rate effects on the strength of rock are related to radial confinement induced by axial strain acceleration, small aspect ratio, and friction constrains. Hao et al [12] proposed empirical relations to eliminate the impacts of the lateral inertia confinement, so as to better explore the strain rate effects. Zhu et al [13] introduced three methods to study the frictional effect between the rock sample and bars. ey analyzed the effects of static axial pressure and lateral pressure and determined the dynamic behavior of rocks under in situ stresses
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
