Robust characterization of viscoelastic materials from measurements of group shear wave speeds
This study describes a new method to determine the stiffness μ0 and viscosity η of viscoelastic materials by observing shear wave propagation following localized, impulsive excitations and measuring the group shear wave speeds Vdisp and Vvel determined using the shear wave displacement and velocity signals, respectively. The stiffness and viscosity are found by analytically solving the equation of motion describing shear wave propagation and calculating lookup tables μ0(Vdisp, Vvel) and η(Vdisp, Vvel) to give μ0 and η from the measured shear wave speeds. Results are presented for three viscoelastic phantoms and one approximately elastic phantom. The method is robust because group shear wave speeds are easily measured experimentally, the lookup tables are relatively insensitive to the size and shape of the excitation, and the difference ΔV = Vvel - Vdisp gives a first order measure of viscosity in the same way that the group shear wave speed gives a measure of the material stiffness.
