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OPUS4-4532 Wissenschaftlicher Artikel Pupyrev, Pavel Dmitrievich; Nedospasov, Ilya; Sokolova, Elena; Mayer, Andreas Surface acoustic waves confined to a soft layer between two stiff elastic quarter-spaces Propagation of acoustic waves is considered in a system consisting of two stiff quarter-spaces connected by a planar soft layer. The two quarter-spaces and the layer form a half-space with a planar surface. In a numerical study, surface waves have been found and analyzed in this system with displacements that are localized not only at the surface, but also in the soft layer. In addition to the semi-analytical finite element method, an alternative approach based on an expansion of the displacement field in a double series of Laguerre functions and Legendre polynomials has been applied. It is shown that a number of branches of the mode spectrum can be interpreted and remarkably well described by perturbation theory, where the zero-order modes are the wedge waves guided at a rectangular edge of the stiff quarter-spaces or waves guided at the edge of a soft plate with rigid surfaces. For elastic moduli and densities corresponding to the material combination PMMA-silicone-PMMA, at least one of the branches in the dispersion relation of surface waves trapped in the soft layer exhibits a zero-group velocity point. Potential applications of these 1D guided surface waves in non-destructive evaluation are discussed. ScienceDirect 2021 NaN Wave Motion 101 102672-1 102672-6 10.1016/j.wavemoti.2020.102672 Fakultät Betriebswirtschaft und Wirtschaftsingenieurwesen (B+W)
OPUS4-3838 Wissenschaftlicher Artikel Pupyrev, Pavel Dmitrievich; Nedospasov, Ilya; Mayer, Andreas Guided acoustic waves at the intersection of interfaces and surfaces In numerical calculations, guided acoustic waves, localized in two spatial dimensions, have been shown to exist and their properties have been investigated in three different geometries, (i) a half-space consisting of two elastic media with a planar interface inclined to the common surface, (ii) a wedge made of two elastic media with a planar interface, and (iii) the free edge of an elastic layer between two quarter-spaces or two wedge-shaped pieces of a material with elastic properties and density differing from those of the intermediate layer. For the special case of Poisson media forming systems (i) and (ii), the existence ranges of these 1D guided waves in parameter space have been determined and found to strongly depend on the inclination angle between surface and interface in case (i) and the wedge angle in case (ii). In a system of type (ii) made of two materials with strong acoustic mismatch and in systems of type (iii), leaky waves have been found with a high degree of spatial localization of the associated displacements, although the two materials constituting these structures are isotropic. Both the fully guided and the leaky waves analyzed in this work could find applications in non-destructive evaluation of composite structures and should be accounted for in geophysical prospecting, for example. A critical comparison is presented of the two computational approaches employed, namely a semi-analytical finite element scheme and a method based on an expansion of the displacement field in a double series of special functions. Amsterdam [u.a.] Elsevier 2019 10 Ultrasonics 95 52 62 10.1016/j.ultras.2019.03.002 Fakultät Betriebswirtschaft und Wirtschaftsingenieurwesen (B+W)