Computational Simulation And Experimental Research On The Wave Propagation In Viscoelastic Bar

The research in this dissertation is concerned with the bar in the viscoelastic SHPB system. The viscoelastic wave propagation in a thin bar and the spectral analysis method are investigated by computational simulation and experimental research.Firstly, the history of Hopkinson technology is looked back. The latest process of viscoelastic Hopkinson technology is introduced, and some problems are also pointed out. It is found that the wave propagation coefficient method is easy to use in the viscoelastic Hopkinson experiment, after the comparison between two spectral analysis methods which are used to investigate the propagation of viscoelastic wave.A computer programme is designed for the wave propagation coefficient method, which is used to calculate the propagation coefficient and predict the wave propagating in the bar. As an example, the propagation coefficient of PMMA is calculated.The bar loaded by several ideal impact pressures or hit by a projectile is analyzed with ABAQUS, then how does the wave propagate in the bar is investigated. In the computational simulation, the ABAQUS user subroutine interface UMAT is used to define the nonlinear Zhu-Wang-Tang (ZWT) constitutive model, and the detailed design of UMAT is discussed. The results of the computational simulation indicate that the wave propagation attenuation and dispersion is obvious. It also shows that the sharper the incident wave is, the faster the amplitude attenuates. After propagating for some distance, the lengths of waves produced by projectiles with different lengths are almost equal. The computational simulation work in this dissertation presents a numerical method to study the viscoelastic SHPB technology.Finally, the viscoelastic wave propagation in the bar and the influenced factors of the propagation coefficient are investigated with a set of experiments. The results of experiments indicate that the higher the velocity of the projectile is, the more serious the wave propagation dispersion is, and the shorter the projectile is, or the sharper the incident wave is , the more obvious the wave propagation attenuation and dispersion is . Further more, it also shows that the propagation coefficient is influenced by the velocity of the projectile, the shape of the incident wave and the diameter of the bar.The work in this dissertation provides basis for viscoelastic SHPB technology.