| Polymers, foam, rubber and other soft materials are widely used in packaging container to protect various types of products as impact resistant material for their better energy absorption property. So test their dynamic mechanical properties attracted attention of more and more people. The experimental technology of viscoelastic bar have been developed for studying the dynamic mechanical properties of viscoelastic materials. In this paper, Based on the experiment of stress propagation in viscoelstic rods, wavelet analysis theory will be used to study the attenuation and dispersion laws for stress propagation in viscoelstic rods. Then waveform prediction will be implemented too.Firstly, research situation of attenuation and dispersion for the stress propagation in viscoelstic rods will be introduced by three aspects: theory,experiment and numerical simulation. Some methods will be discussed and some existing problems will also be pointed out. Then, Design propagation experiment of viscoelastic stress wave and analyze the influence on waveform from different impact velocities, different lengths of projectile and different materials. Through typical signals spectrum analysis, determined the cutoff frequency.Based on Donoho wavelet threshold denoising, four factors that influence the effect of denoising were studied and discussed respectively. In view of the complex wavelet’s amplitude and phase information, the attenuation and dispersion behavior can be got from 3D map of time-scale-amplitude through Gabor continuous wavelet transform. Fitting attenuation coefficient and group velocity for each center frequency by least square method, then the propagation rules in different polymer rods can be got.Predict the waveform through wavelet packet perfect reconstruction. Take the wavelet packet transform on signal, and analyze the frequency-band sequence for each nodes. Then combining the center frequency method with the Cubic Spline Interpolation to Predict the waveform. Finally, Use MATLAB GUI soft programming to realize visualization for data processing, wavelet denoising,attenuation and dispersion analysis, waveform prediction. |
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