Characterization of viscoelastic properties of polymer bar using iterative deconvolution in the time domain

A new approach to characterize the viscoelastic properties of a polymer bar using wave propagation phenomenon that is dominated by attenuation and dispersion is presented. A novel iterative deconvolution algorithm is proposed to directly extract the impulse response function (IRF) from the measured discrete strain signals in the time domain. The algorithm can identify the response of a linear time-invariant system from the measured input and output signals that are often subjected to noise and truncation. The derived IRF is the non-parametric characterization of the viscoelasticity of the polymer bar and is employed to predict strain signal at the next position and/or to retrieve strain signal at a previous position for verification. The parametric representation of the viscoelasticity is implemented on the basis of a universal linear viscoelastic (multiple Maxwell elements) model and the associated frequency response of the derived IRF. A spectrum of viscoelastic parameters was identified for the polymer bar and the results are presented. As an application example of this approach, a data reduction procedure to extract the high strain rate response of low impedance materials from strain signals obtained from a polymer split Hopkinson pressure bar is presented.