Broadband ultrasonic spectroscopy for the characterization of viscoelastic materials

• Paper addresses a method for the characterization of linear viscoelastic materials.
• Method is based on acoustic through transmission technique.
• Method can be used in 20–400 kHz range.
• Spherical wave is used to characterize the material.
• Spreading error caused by the spherical wave is eliminated by using diffraction correction method developed for focused transducers.
• Method is validated on PMMA.
• Method is capable of material properties of soft matter.

In this study, non-destructive experimental method based on acoustic through transmission technique along with broadband spectroscopy is proposed in order to determine the linear viscoelastic material properties in 20–400 kHz range. Material properties such as phase velocity and attenuation coefficient of longitudinal and shear waves are measured. Diffraction correction developed for focused transducers is used to eliminate the spreading error due to the spherical wave generated by the hydrophone which is used as a transmitter. Method is validated on polymethyl methacrylate (PMMA). Both longitudinal wave velocity, shear wave velocity and attenuation coefficient of longitudinal wave of PMMA are in agreement with the previously reported values which are given in the literature. Attenuation coefficient of shear wave in PMMA is measured successfully and in agreement with the theoretical predictions. Longitudinal wave velocity and corresponding attenuation coefficient of gelatine gel are also measured.