Effect of viscoelastic coating on Lamb wave propagation in plates

Abstract

Dispersion curves for elastic multilayer plates are useful to describe the behavior of guided wave modes in composite materials. They provide information to set up the appropriate launching conditions of the guided waves for assuring high scanning distances with sensitivity. This paper applies an efficient Gauss-Lobatto-Legendre (GLL) collocation method to formulate the Scaled Boundary Finite Element Method SBFEM to estimate the dispersion curves and wave structure in metallic plates with viscoelastic coatings. This formulation is quite efficient because it discretize the cross-section of each layer with only one spectral element. As a result, a global stiffness matrix is obtained by assembling the stiffness matrices of each layer. The formulation leads to a first-order eigenvalue problem by implementing the Z coefficient matrix that can be efficiently solved to compute the (ω, k) couples that guarantee the wave modes propagating in the structure. The estimated phase velocity and group velocity curves for coated and free plates show a small frequency shifting exhibited in some modes, with predominant displacement in the viscoelastic layer of the wave displacement profile.