SH waves travel with a layered elastic semi-space considering surface, nonlocal, and strain gradient effects

With flourishing development in 5G wireless communication and non-destructive tests, the mechanical attributes of ultrahigh-frequency surface acoustic waves should spark considerable attraction. At the same time, the wavelength of surface acoustic waves arrives at micrometers, while the operational frequency of surface waves outperforms 1 GHz. Thereupon, the wavelengths of the GHz and THz waves are so small that size effects must be involved. Furthermore, to explicitly quantify the influence of the gradient elasticity of the bulk and surface layers on the shear horizontal (SH) waves’ properties, we consider the surface stress, the nonlocal, and gradient elastic theories to obtain the phase velocity equations of the SH wave in an elastic nanoplate overlaid on an elastic half-space. It is concluded that the gradient elasticity plays a paramount role in the attributes of SH waves, while the operational frequency or wavelength is ultrahigh or ultrasmall. In addition, we examine a case in which no waves are in the structure, considering strain gradients. It is valid if the elastic layer thickness, h, significantly exceeds the strain gradient constant, l₂. The research could offer a workflow for triggering burgeoning developments of the fabrication of the high-performance SAW nanosensors.