title: Ultrasonic guided wave propagation across waveguide transitions: energy transfer and mode conversion.
abstract: Ultrasonic guided wave inspection of structures containing adhesively bonded joints requires an understanding of the interaction of guided waves with geometric and material discontinuities or transitions in the waveguide. Such interactions result in mode conversion with energy being partitioned among the reflected and transmitted modes. The step transition between an aluminum layer and an aluminum-adhesive-aluminum multi-layer waveguide is analyzed as a model structure. Dispersion analysis enables assessment of (i) synchronism through dispersion curve overlap and (ii) wavestructure correlation. Mode-pairs in the multi-layer waveguide are defined relative to a prescribed mode in a single layer as being synchronized and having nearly perfect wavestructure matching. Only a limited number of mode-pairs exist, and each has a unique frequency range. A hybrid model based on semi-analytical finite elements and the normal mode expansion is implemented to assess mode conversion at a step transition in a waveguide. The model results indicate that synchronism and wavestructure matching is associated with energy transfer through the step transition, and that the energy of an incident wave mode in a single layer is transmitted almost entirely to the associated mode-pair, where one exists. This analysis guides the selection of incident modes that convert into transmitted modes and improve adhesive joint inspection with ultrasonic guided waves.
authors: 212 Engineering Science and Mechanics, Pennsylvania State University, University Park, Pennsylvania 16802, USA. kumarpp@gmail.com
authors: Padmakumar
authors: P
authors: Puthillath
authors: Jose M
authors: JM
authors: Galan
authors: Baiyang
authors: B
authors: Ren
authors: Cliff J
authors: CJ
authors: Lissenden
authors: Joseph L
authors: JL
authors: Rose
mesh_terms: D000269:Adhesives; D000535:Aluminum; D004735:Energy Transfer; D020342:Finite Element Analysis; D008422:Materials Testing; D008962:Models, Theoretical; D009038:Motion; D013016:Sound; D013997:Time Factors; D014465:Ultrasonics
chemical_list: D000269:Adhesives; D000535:Aluminum