Abstract
Rayleigh waves influenced by surface effect are investigated by using finite element methods, in which eigenfrequency analysis are performed on a model composed of a half-space covered by the surface effect dominated domain. For a given wavelength, the frequency of the Rayleigh wave is obtained as the eigenfrequency of the model satisfying Floquet periodic boundary conditions. The thickness of the surface effect can be set to be infinitely small or a finite value in the finite element methods. The curvature-dependent out-of-plane force induced by surface tension as described by the generalized Young-Laplace equation is realized through geometric nonlinear analysis. The finite element simulations show that the assumptions of small curvature and infinitely small thickness of the surface effect widely used in theoretical approaches become invalid when Rayleigh waves are highly influenced by the surface effect. This work gives a more accurate insight into the surface effect on Rayleigh waves and provides a potential method for measuring the thickness of the surface effect from the dispersion curves of surface effect influenced Rayleigh wave velocities.
Highlights
In solids, acoustic waves with frequencies of ∼ 101 GHz to ∼ 100 THz can be generated by absorbing femtosecond laser light and such waves can be detected by optical probes after traveling on the surfaces or the interior domain of the solids.[1,2,3,4] Since the wavelengths of sub-THz and THz acoustic waves are typically in the order of 100 nm to 102 nm, advances in generating and probing sub-THz and THz acoustic waves herald a powerful method for observing the mechanical behavior of nanoscaled materials
We focus on Finite element (FE) modeling the surface effect on stiff solids
As d increases from 0.3 nm to 1.0 nm, Rayleigh wave velocity decreases and the maximum possible frequency decreases. This information provides a potential method for measuring the thickness of the surface effect in future THz Rayleigh wave experiments
Summary
Acoustic waves with frequencies of ∼ 101 GHz to ∼ 100 THz can be generated by absorbing femtosecond laser light and such waves can be detected by optical probes after traveling on the surfaces or the interior domain of the solids.[1,2,3,4] Since the wavelengths of sub-THz and THz acoustic waves are typically in the order of 100 nm to 102 nm, advances in generating and probing sub-THz and THz acoustic waves herald a powerful method for observing the mechanical behavior of nanoscaled materials. Major assumptions are widely used in the theoretical approaches for modeling the surface effect on wave propagation in solids. The first assumption is that, taking two dimensional case as an example, the curvature of solid surfaces during deformation is so small that the curvature is approximated as the second derivative of normal displacement with respect to tangential coordinate. The dispersion curves of the Rayleigh waves with the surface effect considered are obtained by performing eigenfrequency analysis of the solids with Floquet periodic boundary conditions. Despite of the tremendous difference in the frequency ranges, the fundamental mechanism for the surface tension effect on Rayleigh waves in stiff solids and soft solids is the same. We focus on FE modeling the surface effect on stiff solids
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
