No abstract

No abstract

Mechanical properties of the human vocal fold cover layer were experimentally investigated in uniaxial and biaxial tensile tests. The results showed a coupling effect between the stress conditions along the anterior-posterior and transverse directions, with vocal fold elongation increasing vocal fold stiffness along both directions, thus allowing more efficient control of the fundamental frequency of voice through vocal fold elongation. This study also shows that vocal folds were nearly isotropic at resting conditions, thus a tendency to vibrate with incomplete glottal closure, but became increasingly anisotropic with increasing vocal fold elongation. IntroductionThe mechanical conditions within the human vocal folds play an important role in determining the fundamental frequency of vocal fold vibration and the resulting voice quality. As the vocal folds are postured for the production of different voice types, the mechanical conditions are also expected to vary (Hirano, 1974). A better understanding of the mechanical conditions of the vocal folds across different voice types would facilitate the development of biomaterials for vocal fold injection or tissue engineered vocal fold replacement with similar material properties. Computationally, a more quantitative characterization of the vocal fold mechanical properties would provide data for developing material constitutive models, linear or nonlinear, for use in computational models of phonation.There have been many previous reports experimentally characterizing vocal fold mechanical properties (e.g., Hirano and Kakita, 1985;Alipour-Haghighi and Titze, 1991;Haji et al., 1992;Chan and Titze, 1999;Alipour and Vigmostad, 2012;Kelleher et al., 2013;Kazemirad et al., 2014). While these studies have provided valuable contribution to our understanding of the vocal fold mechanical properties, most of these studies were performed in a uniaxial tensile test, different from the physiological conditions in which vocal folds are subject to tensions or constraints along multiple directions. Although elongating the vocal folds along the anterior-posterior (AP) direction increases vocal fold stiffness and tension along this direction, which is considered the primary means of regulating the fundamental frequency (F0) of voice (Titze, 1994;Zhang, 2016b), little is known about how vocal fold elongation affects the mechanical conditions in the transverse plane (the plane perpendicular to the AP direction), which may also contribute to F0 control. Previous studies have shown a cross-axis coupling effect such that AP elongation may also stiffen the vocal folds in the transverse plane (e.g., Yin and Zhang, 2013). With this extra vocal fold stiffening in the transverse plane, vocal fold elongation would be more effective in regulating the overall vocal fold stiffness and F0 of vocal fold vibration, compared to F0 control through varying the stiffness and tension along the AP direction alone. This cross-axis coupling effect of vocal fold elongation cannot be investigated in a ...

No abstract

Interface delaminations between individual plies in a composite, or disbonds of face sheets in honeycomb structures often remain undetected. Using guided ultrasonic waves (Rayleigh and Lamb waves) such hidden defects can be detected. In this work, an analytical framework that considers propagating, nonpropagating and evanescent waves to analyze the scattering of an incident ultrasonic wave at a delamination-like discontinuity is presented. Wave conversion at the interface of the damage is quantified in terms of the power flows of the individual waves. The analytical solutions are compared with results from numerical simulations. For an incident Lamb wave, excellent agreement is found. However, it is shown that the analytical solution for an incident Rayleigh wave has significant differences from the numerical results, due to the incomplete nature of the Rayleigh wave-field in the half-space. Even though this study is performed for isotropic waveguides, the method can be extended to transversely isotropic laminates by substituting the corresponding expressions for the dispersion equations, as well as displacement and stress fields.