Multiple-mode Lamb wave scattering simulations using 3D elastodynamic finite integration technique

• Published in: Ultrasonics Vol. 52; no. 2; pp. 193 - 207
• Main Authors: Leckey, Cara A.C., Rogge, Matthew D., Miller, Corey A., Hinders, Mark K.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.02.2012; Elsevier
• Subjects: Acoustical measurements and instrumentation; Acoustics; Computer simulation; Defects; Elastodynamics; Exact sciences and technology; Finite Element Analysis; Fundamental areas of phenomenology (including applications); Lamb waves; Linear acoustics; Mathematical analysis; Nondestructive evaluation; Physics; Rectangles; Scattering; Simulation; Solid mechanics; Structural acoustics and vibration; Structural and continuum mechanics; Three dimensional; Ultrasonics - methods; Vibration, mechanical wave, dynamic stability (aeroelasticity, vibration control...); Lamb waves; Simulation; Nondestructive evaluation; Waveform; Hole; Surface wave; Aluminium; Overlap; Elastic wave; Multiple scattering; Experimental study; Modeling; Multiple wave; Plate; Thickness; Lamb wave; Phase velocity; Group velocity; Wave scattering; Elastodynamics; Aircraft; Non destructive test; Comparative study; Damaging
• ISSN: 0041-624X; 1874-9968
• DOI: 10.1016/j.ultras.2011.08.003

► We simulate 3D Lamb wave interaction with flaws in aluminum plates and compare to experimental data. ► The plate thickness leads to the existence of numerous dispersive Lamb wave modes at once. ► The multiple modes require a unique way to make comparisons to experimental data. ► Results compare well with experiment and provide insight into multiple mode Lamb wave behavior. ► We also show that 3D simulations can explore other complicated flaw situations related to NDE. We have implemented three-dimensional (3D) elastodynamic finite integration technique (EFIT) simulations to model Lamb wave scattering for two flaw-types in an aircraft-grade aluminum plate, a rounded rectangle flat-bottom hole and a disbond of the same shape. The plate thickness and flaws explored in this work include frequency–thickness regions where several Lamb wave modes exist and sometimes overlap in phase and/or group velocity. For the case of the flat-bottom hole the depth was incrementally increased to explore progressive changes in multiple-mode Lamb wave scattering due to the damage. The flat-bottom hole simulation results have been compared to experimental data and are shown to provide key insight for this well-defined experimental case by explaining unexpected results in experimental waveforms. For the rounded rectangle disbond flaw, which would be difficult to implement experimentally, we found that Lamb wave behavior differed significantly from the flat-bottom hole flaw. Most of the literature in this field is restricted to low frequency–thickness regions due to difficulties in interpreting data when multiple modes exist. We found that benchmarked 3D EFIT simulations can yield an understanding of scattering behavior for these higher frequency–thickness regions and in cases that would be difficult to set up experimentally. Additionally, our results show that 2D simulations would not have been sufficient for modeling the complicated scattering that occurred.