Interpretation of shear material properties of vocal fold mucosal tissues with Fung’s quasilinear viscoelastic theory

Abstract

Fung’s quasilinear viscoelastic theory (QLV) [Y. C. Fung, Biomechanics (Springer-Verlag, New York, 1993), pp. 277–292] has been successfully applied to model the time- and history-dependent properties of a variety of biological soft tissues in the passive state. In particular, the hysteresis or damping curves of many soft tissues remain relatively insensitive to the rate of deformation (strain rate or frequency) across several decades of variation. This insensitivity to frequency cannot readily be accounted for by traditional discrete models of linear viscoelasticity. Rather, Fung’s QLV provides a mathematically powerful framework in which a continuous stress relaxation spectrum can be used to model the relatively flat damping characteristics. The shear properties of human vocal fold mucosal tissues were measured with a rotational rheometer. Data on complex dynamic shear modulus, complex dynamic viscosity, and damping ratio as functions of frequency were obtained. It was found that vocal fold mucosal tissues show the shear-thinning behavior and have a relatively flat damping curve typical of biological soft tissues. Theoretical predictions based on the QLV matched well with the empirical data. The results suggest that the vocal fold mucosa can be modeled by the QLV under small-amplitude oscillation conditions. [Work supported by NIH Grant No. P60 DC00976.]