Propagation Characteristics And Numerical Simulation Of Rayleigh Wave On Curved Surface In Inhomogeneous Media

In ultrasonic testing body waves always produce some unwanted reflections in the structure,which affects the detection effect of complex shaped industrial products.However,Rayleigh surface waves can be propagated on smooth surfaces almost unimpeded.Therefore,Rayleigh wave is often used to detect surface bending,surface cracks and coating thickness.At the same time,Rayleigh wave can also be used to design electro-acoustic delay device,because the delay effect of Rayleigh wave in the surface.In view of Rayleigh wave's wide range of applications on surface structure,this paper focuses on Rayleigh wave's propagation in the inhomogeneous medium surface.In this paper,we first use the WKB method(Wentzel-Kramers-Brillouin method),and consider influences of the main curvature radius(the curvature radius along the direction of propagation and perpendicular to the propagation direction)on the Rayleigh wave.The differential equation of motion of Rayleigh wave on the surface is solved and the approximate analytical expression of Rayleigh wave velocity and radius of curvature is obtained.The basic characteristics of Rayleigh wave propagating on the surface are preliminarily described.In order to analyze these problems more accurately,based on the geometric characteristics of Gaussian surface,a semi-analytical expression for general surface is derived by semi-analytical finite method.Several typical uniform engineering surfaces are analyzed by using semi-analytical expressions structure.Finally,the propagation properties of Rayleigh wave on a special surface model with coating are modeled by the semi-analytical expression and are affected by the frequency,the material and the thickness of the overburden.And we can thus deduce the material and thickness of the overlay.