EXPERIMENTAL STUDY FOR DISPERSION AND ATTENUATION CORRECTION IN VISCOELASTIC SPLIT HOPKINSON PRESSURE BAR ARRANGEMENT

Abstract

Split Hopkinson pressure Bar (SHPB) arrangement is the most practical and accurate method for studying dynamic mechanical behavior of materials under high strain rate. However in case of studying foams, and soft tissues (low impedance materials) a modified version of SHPB with bars made from a viscoelastic material like Poly methyl methacrylate PMMA acrylate is commonly used .so a good prediction of the stress waves and particle velocity acting at the interface between bars and specimen taking into account the dispersion and attenuation effect is essential. In this study the wave propagation coefficient as a function of the phase velocity and the attenuation coefficient in relation to the frequency are calculated experimentally by a set of free end bar tests using a cylindrical projectile to the circumstances of stepped velocity and different firing pressure. Correction processes for longitudinal stains related to incident and reflected waves are preceded in frequency domain using Fast Fourier Transformer (FFT) technique.