Global–local model for three-dimensional guided wave scattering with application to rail flaw detection

Abstract

This study presents a three-dimensional global–local formulation for the prediction of guided wave scattering from discontinuities (e.g. defects). The approach chosen utilizes the Semi-Analytical Finite Element method for the “global” portion of the waveguide, and a full Finite Element discretization for the “local” portion of the waveguide containing the discontinuity. The application of interest is the study of guided wave scattering from transverse head defects in rails. Theoretical scattering results are impossible to obtain in this case for a wide-frequency range. While three-dimensional Semi-Analytical Finite Element–Finite Element models for guided wave scattering studies have been used in the past, this is the only study where guided waves in rails were modeled in a wide-frequency range (up to 180 kHz). A comparison analysis with a benchmark study of wave reflections from the free end of a cylindrical rod is conducted first. For the case of the rail, selected case studies of incoming guided modes were chosen, and reflection and transmission spectra are calculated for head defects of various sizes. This kind of results can be utilized to guide and/or interpret ultrasonic guided wave tests aimed at defect detection or quantification. Finally, parametric studies are conducted to examine more closely the role of certain operational parameters that are important in this kind of analysis, and specifically the size of the “local” region and the number of guided modes considered. These parametric studies lead to compromises that need to be struck on the basis of conservation of energy among all wave modes involved.

The role of evanescent modes in global-local analysis of ultrasonic guided waves in plates with varying local zone-scatterer relations

“…In this paper, the authors study the role of evanescent modes in the accurate modeling of UGWs scattering in isotropic and composite plate waveguides, with respect to defect shapes and sizes. The hybrid GL method, expanded by the authors and applied on complex composite structures and 3D geometries (Spada et al (2020); Spada et al (2022)), is here used and its accuracy is assessed through energy balance to provide considerations in terms of the local FE zone and scatterer relation.…”

Advancing measurement of zero-group-velocity Lamb waves using PVDF-TrFE transducers: first data and application to in situ health monitoring of multilayer bonded structures

“…Numerous methods exploiting the guided ultrasonic waves (GUWs) have been developed and applied to detect the defects and assess the health conditions of engineering structures, among which methods based on specific wave modes have manifested applicability to structures with complex geometries. For example, methods based on diffused ultrasonic waves, 1–6 featured-GUWs, 7–9 numerical analysis-driven methods 10–15 have been intensively studied and applied. Although these methods have proved their effectiveness for monitoring structures with irregular sections, it is almost a consensus that the interpretation of interactions of GUWs with defect in these methods is fairly challenging.…”