# Engineering Mechanics

Proceedings Vol. 32 (2026)

ENGINEERING MECHANICS 2026

Copyright © 2026 Institute of Thermomechanics of the Czech Academy of Sciences, Prague

 

Fíla T., Falta J.
pages 41 - 44, full text

The Split Hopkinson Pressure Bar (SHPB) technique is widely used for high strain-rate characteri- zation, but its application to low-impedance materials is limited by low signal amplitudes and poor signal-to- noise ratio in conventional metallic bars. Polymeric viscoelastic bars offer improved sensitivity but introduce wave dispersion, complicating signal interpretation. This study proposes a simplified approach combining a linear elastic aluminium input bar with a viscoelastic polyamide output bar and a wave separation technique based on simultaneous strain and velocity measurements at a single location. Instead of employing complex viscoelastic models, an effective linear elastic representation of the viscoelastic bar is calibrated using void tests. The results show that the approach is only valid when the frequency bandwidth of the stress wave is sufficiently reduced. Without pulse shaping (mechanical filtering), strong dispersion leads to significant dis- crepancies in measured signals. By introducing a soft copper pulse shaper, high-frequency components are suppressed, enabling accurate reconstruction of force and velocity using the simplified model. The method is successfully demonstrated on a very low-impedance material, where the polymeric bar provides significantly improved signal quality compared to a conventional metallic bar.

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All papers were reviewed by members of the scientific committee.