Compression pulse attenuation in polymethylmethacrylate

Numerical investigation is carried out in viscoelastic and hydrodynamic approximations of the shock waves dynamics, which arising in the case of a plane high-velocity impact of plate, and also when pressure pulses of micro-, nano- and picosecond durations are applied to the polymethylmethacrylate (PMMA) surface. For PMMA, the difference in amplitude between calculations in the hydrodynamic and the viscoelastic approximations is about 20%. The amplitude of the shock compression pulse in the viscoelastic approximation, in comparison with the hydrodynamic one, is greater for shallow depths due to additional rigidity, and is smaller for large depths due to the higher propagation velocity of the unloading wave catching the front of the shock wave. An investigation was made for the compression pulse attenuation in model polymers with variable parameters of the viscoelasticity model. The increase in the relaxation time and the yield point leads to a transition to the elastic behavior. At the same time, even for small relaxation times and yield limits, the damping curves at large depths differ from the hydrodynamic approximation due to the higher velocity of the unloading wave.